livecodingspace-app/public/core/vwf.js

/*
The MIT License (MIT)
Copyright (c) 2014-2020 Nikolai Suslov and the Krestianstvo.org project contributors. (https://github.com/NikolaySuslov/livecodingspace/blob/master/LICENSE.md)

Virtual World Framework Apache 2.0 license  (https://github.com/NikolaySuslov/livecodingspace/blob/master/licenses/LICENSE_VWF.md)
*/

/// @module vwf

/// vwf.js is the main Virtual World Framework manager. It is constructed as a JavaScript ES6 module
/// to isolate it from the rest of the  page's JavaScript environment. The vwf module self-creates its own instance when loaded and
/// attaches to the global window object as window.vwf. Nothing else should affect the global environment.

import { Helpers } from '/core/helpers.js';
import { VirtualTime } from '/core/virtualTime.js';
import { ReflectorClient } from '/core/reflectorClient.js';
import { Luminary } from '/core/luminary.js';

import { Logger } from '/core/vwf/utility/logger.js';
import { KUtility } from '/core/vwf/utility/kutility.js';
import { Utility } from '/core/vwf/utility/utility.js';
import { XPath } from '/core/vwf/utility/xpath.js';

import { Fabric } from '/core/vwf/fabric.js';
import { ViewKernel } from '/core/vwf/view.js';
import { ModelKernel } from '/core/vwf/model.js';
import { Log } from '/core/vwf/model/stage/log.js';

class VWF {

    constructor(driverConf, proxy, doc, connectionConf) {
        console.log("VWF constructor");

        let self = this;

        this.helpers = new Helpers;

        this.driverConfiguration = driverConf || {};
        this.proxy = proxy;
        this.doc = doc;

        this.isLuminary = connectionConf.luminary;
        this.isLuminaryGlobalHB = connectionConf.luminaryHB;
        this.luminaryGlobalHBPath = connectionConf.luminaryGlobalHBPath;


        this.luminary = new Luminary;
        this.reflectorClient = new ReflectorClient;
        this.virtualTime = new VirtualTime;
        window._Time = this.virtualTime; //vwf.virtualTime = app.virtualTime;

        this.applicationLoad = undefined;

        // == Public variables =====================================================================

        /// The runtime environment (production, development, testing) and other configuration
        /// settings appear here.
        /// 
        /// @name module:vwf.configuration
        /// 
        /// @private

        /// Default configuration for all environments.

        this.configuration = {
            "log-level": "info",                  // logger threshold
            "random-seed": +new Date,             // pseudorandom number generator seed
            "randomize-ids": true,               // randomize IDs to discourage assumptions about ID allocation
            "humanize-ids": true,                // append recognizable strings to node IDs
            "preserve-script-closures": false,    // retain method/event closures by not serializing functions (breaks replication, persistence)
            "load-timeout": 30                   // resource load timeout in seconds
        }


        //undefined; // require( "vwf/configuration" ).active; // "active" updates in place and changes don't invalidate the reference  // TODO: assign here after converting vwf.js to a RequireJS module and listing "vwf/configuration" as a dependency

        /// Kernel utility functions and objects.
        /// 
        /// @name module:vwf.utility
        /// 
        /// @private

        this.kutility = new KUtility;
        //this.kutility = undefined; // require( "vwf/kernel/utility" );  // TODO: assign here after converting vwf.js to a RequireJS module and listing "vwf/kernel/utility" as a dependency


        this.xpath = new XPath;
        this.utility = new Utility;

        this.viewModule = new Fabric({
            id: "vwf/view"
        }, 'View');

        this.modelModule = new Fabric({
            id: "vwf/model"
        }, 'Model');


        /// The kernel logger.
        /// 
        /// @name module:vwf.logger
        /// 
        /// @private

        this.logger = (new Logger).for("vwf", this, this.configuration["log-level"]);

        //undefined; // require( "logger" ).for( undefined, this );  // TODO: for( "vwf", ... ), and update existing calls  // TODO: assign here after converting vwf.js to a RequireJS module and listing "vwf/logger" as a dependency

        /// Each model and view module loaded by the main page registers itself here.
        /// 
        /// @name module:vwf.modules
        /// 
        /// @private

        this.modules = [];

        /// vwf.initialize() creates an instance of each model and view module configured on the main
        /// page and attaches them here.
        /// 
        /// @name module:vwf.models
        /// 
        /// @private

        this.models = [];

        /// vwf.initialize() creates an instance of each model and view module configured on the main
        /// page and attaches them here.
        /// 
        /// @name module:vwf.views
        /// 
        /// @private

        this.views = [];

        /// this.models is a list of references to the head of each driver pipeline. Define an
        /// `actual` property that evaluates to a list of references to the pipeline tails. This is
        /// a list of the actual drivers after any intermediate stages and is useful for debugging.
        /// 
        /// @name module:vwf.models.actual

        Object.defineProperty(this.models, "actual", {

            get: function () {

                // Map the array to the result.

                var actual = this.map(function (model) {
                    return last(model);
                });

                // Map the non-integer properties too.

                for (var propertyName in this) {
                    if (isNaN(Number(propertyName))) {
                        actual[propertyName] = last(this[propertyName]);
                    }
                }

                // Follow a pipeline to the last stage.

                function last(model) {
                    while (model.model) model = model.model;
                    return model;
                }

                return actual;
            }

        });

        /// this.views is a list of references to the head of each driver pipeline. Define an
        /// `actual` property that evaluates to a list of references to the pipeline tails. This is
        /// a list of the actual drivers after any intermediate stages and is useful for debugging.
        /// 
        /// @name module:vwf.views.actual

        Object.defineProperty(this.views, "actual", {

            get: function () {

                // Map the array to the result.

                var actual = this.map(function (model) {
                    return last(model);
                });

                // Map the non-integer properties too.

                for (var propertyName in this) {
                    if (isNaN(Number(propertyName))) {
                        actual[propertyName] = last(this[propertyName]);
                    }
                }

                // Follow a pipeline to the last stage.

                function last(model) {
                    while (model.model) model = model.model;
                    return model;
                }

                return actual;
            }

        });

        /// The identifer assigned to the client by the server.
        /// 
        /// @name module:vwf.moniker_
        /// 
        /// @private

        this.moniker_ = undefined;

        /// Nodes that are receiving ticks.
        /// 
        /// @name module:vwf.tickable
        /// 
        /// @private

        this.tickable = {
            // models: [],
            // views: [],
            nodeIDs: [],
        };

        // == Private variables ====================================================================

        /// @name module:vwf.private
        /// 
        /// @private

        this.private = {}; // for debugging

        /// Components describe the objects that make up the simulation. They may also serve as
        /// prototype objects for further derived components. External components are identified by
        /// URIs. Once loaded, we save a mapping here from its URI to the node ID of its prototype so
        /// that we can find it if it is reused. Components specified internally as object literals
        /// are anonymous and are not indexed here.
        /// 
        /// @name module:vwf~components

        this.components = this.private.components = {}; // maps component node ID => component specification

        // Each node is assigned an ID as it is created. This is the most recent ID assigned.

        // Communication between the manager and the models and views uses these IDs to refer to the
        // nodes. The manager doesn't maintain any particular state for the nodes and knows them
        // only as their IDs. The models work in federation to provide the meaning to each node.

        // var lastID = 0;

        /// Callback functions defined in this scope use this local "vwf" to locate the manager.
        /// 
        /// @name module:vwf~vwf

        window.vwf = this;


        //////////
        this.setProperty.entrants = {}; // maps ( nodeID + '-' + propertyName ) => { index: i, value: v }
        this.getProperty.entrants = {}; // maps ( nodeID + '-' + propertyName ) => { index: i, value: v }


        // == Private variables ====================================================================

        /// Prototype for name-based, unordered collections in the node registry, including
        /// `node.properties`, `node.methods`, and `node.events`.

        this.keyedCollectionPrototype = {

            /// Record that a property, method or event has been created.
            /// 
            /// @param {String} name
            ///   The member name.
            /// @param {Boolean} changes
            ///   For patchable nodes, record changes so that `kernel.getNode` may create a patch
            ///   when retrieving the node.
            /// @param [value]
            ///   An optional value to assign to the record. If `value` is omitted, the record will
            ///   exist in the collection but have the value `undefined`.
            /// 
            /// @returns {Boolean}
            ///   `true` if the member was successfully added. `false` if a member by that name
            ///   already exists.

            create: function (name, changes, value) {

                if (!this.hasOwn(name)) {

                    this.makeOwn("existing");

                    // Add the member. `Object.defineProperty` is used instead of
                    // `this.existing[name] = ...` since the prototype may be a behavior proxy, and
                    // the accessor properties would prevent normal assignment.

                    Object.defineProperty(this.existing, name,
                        self.configurable(value ? value : undefined));

                    if (changes) {

                        this.makeOwn("changes");

                        if (this.changes[name] !== "removed") {
                            this.changes[name] = "added";
                        } else {
                            this.changes[name] = "changed"; // previously removed, then added
                        }

                        if (this.container && this.containerMember) {
                            this.container.change(this.containerMember);
                        }

                    }

                    return true;
                }

                return false;
            },

            /// Record that a member has been deleted.
            /// 
            /// @param {String} name
            ///   The member name.
            /// 
            /// @returns {Boolean}
            ///   `true` if the member was successfully removed. `false` if a member by that name
            ///   does not exist.

            delete: function (name, changes) {

                if (this.hasOwn(name)) {

                    delete this.existing[name];

                    if (changes) {

                        this.makeOwn("changes");

                        if (this.changes[name] !== "added") {
                            this.changes[name] = "removed";
                        } else {
                            delete this.changes[name]; // previously added, then removed
                        }

                        if (this.container && this.containerMember) {
                            this.container.change(this.containerMember);
                        }

                    }

                    return true;
                }

                return false;
            },

            /// Record that a member has changed.
            /// 
            /// @param {String} name
            ///   The member name.
            /// 
            /// @returns {Boolean}
            ///   `true` if the change was successfully recorded. `false` if a member by that name
            ///   does not exist.

            change: function (name, value) {

                if (this.hasOwn(name)) {

                    this.makeOwn("changes");

                    if (this.changes[name] !== "added") {
                        this.changes[name] = value ?
                            value : this.changes[name] || "changed";
                    }

                    if (this.container && this.containerMember) {
                        this.container.change(this.containerMember);
                    }

                    return true;
                }

                return false;
            },

            /// Determine if a node has a member with the given name, either directly on the node or
            /// inherited from a prototype.
            /// 
            /// @param {String} name
            ///   The member name.
            /// 
            /// @returns {Boolean}

            has: function (name) {
                return name in this.existing;
            },

            /// Determine if a node has a member with the given name. The node's prototypes are not
            /// considered.
            /// 
            /// @param {String} name
            ///   The member name.
            /// 
            /// @returns {Boolean}

            // Since prototypes of the collection objects mirror the node's prototype chain,
            // collection objects for the proto-prototype `node.vwf` intentionally don't inherit
            // from `Object.prototype`. Otherwise the Object members `hasOwnProperty`,
            // `isPrototypeOf`, etc. would be mistaken as members of a VWF node.

            // Instead of using the simpler `this.existing.hasOwnProperty( name )`, we must reach
            // `hasOwnProperty through `Object.prototype`.

            hasOwn: function (name) {
                return Object.prototype.hasOwnProperty.call(this.existing, name);
            },

            /// Hoist a field from a prototype to the collection in preparation for making local
            /// changes.
            /// 
            /// If the field in the prototype is an object, create a new object with that field as
            /// its prototype. If the field in the prototype is an array, clone the field since
            /// arrays can't readily serve as prototypes for other arrays. In other cases, copy the
            /// field from the prototype. Only objects, arrays and primitive values are supported.
            /// 
            /// @param {String} fieldName
            ///   The name of a field to hoist from the collection's prototype.

            makeOwn: function (fieldName) {

                if (!this.hasOwnProperty(fieldName)) {

                    if (this[fieldName] instanceof Array) {
                        this[fieldName] = this[fieldName].slice(); // clone arrays
                    } else if (typeof this[fieldName] === "object" && this[fieldName] !== null) {
                        this[fieldName] = Object.create(this[fieldName]); // inherit from objects
                    } else {
                        this[fieldName] = this[fieldName]; // copy primitives
                    }

                }

            },

            /// The property, method, or event members defined in this collection.
            /// 
            /// `existing` is an unordered collection of elements and optional values. The keys are
            /// the primary data. Existence on the object is significant regardless of the value.
            /// Some collections store data in the element when the kernel owns additional details
            /// about the member. Values will be `undefined` in other collections.
            /// 
            /// For each collection, `existing` is the authoritative list of the node's members. Use
            /// `collection.hasOwn( memberName )` to determine if the node defines a property,
            /// method or event by that name.
            /// 
            /// The prototype of each `existing` object will be the `existing` object of the node's
            /// prototype (or a proxy to the top behavior for nodes with behaviors). Use
            /// `collection.has( memberName )` to determine if a property, method or event is
            /// defined on the node or its prototypes.

            existing: Object.create(null
                // name: undefined,
                // name: { ... } -- details
                // ...
            ),

            /// The change list for members in this collection.
            /// 
            /// For patchable nodes, `changes` records the members that have been added, removed, or
            /// changed since the node was first initialized. `changes` is not created in the
            /// collection until the first change occurs. Only the change is recorded here. The
            /// state behind the change is retrieved from the drivers when needed.

            changes: {
                // name: "added"
                // name: "removed"
                // name: "changed"
                // name: { ... } -- changed, with details
                // ...
            },

            /// The parent collection if this collection is a member of another. Changes applied to
            /// members of this collection will call `container.change( containerMember )` to also
            /// set the change flag for the containing member.
            /// 
            /// For example, members of the `node.events` collection contain listener collections at
            /// `node.events.existing[name].listeners`. Each listener collection knows its event
            /// name and points back to `node.events`. Changing a listener will call
            /// `node.events.change( name )` to mark the event as changed.

            container: undefined,

            /// This collection's name in the parent if this collection is a member of another
            /// collection. Changes to members of this collection will mark that member changed in
            /// the containing collection.

            containerMember: undefined,

        }

        /// Prototype for index-based, ordered collections in the node registry, including
        /// `event.listeners`.

        this.indexedCollectionPrototype = {

            /// Record that a member has been created.
            /// 
            /// @param {string|number|boolean|null} id
            ///   The member's unique id.
            /// @param {Boolean} changes
            ///   For patchable nodes, record changes so that `kernel.getNode` may create a patch
            ///   when retrieving the node.
            /// 
            /// @returns {Boolean}
            ///   `true` if the member was successfully added. `false` if a member with that id
            ///   already exists.

            create: function (id, changes) {

                if (!this.hasOwn(id)) {

                    this.makeOwn("existing");
                    this.existing.push(id);

                    if (changes) {

                        this.makeOwn("changes");

                        var removedIndex = this.changes.removed ?
                            this.changes.removed.indexOf(id) : -1;

                        if (removedIndex < 0) {
                            this.changes.added = this.changes.added || [];
                            this.changes.added.push(id);
                        } else {
                            this.changes.removed.splice(removedIndex, 1);
                            this.changes.changed = this.changes.changed || [];
                            this.changes.changed.push(id);
                        }

                        if (this.container && this.containerMember) {
                            this.container.change(this.containerMember);
                        }

                    }

                    return true;
                }

                return false;
            },

            /// Record that a member has been deleted.
            /// 
            /// @param {string|number|boolean|null} id
            ///   The member's unique id.
            /// 
            /// @returns {Boolean}
            ///   `true` if the member was successfully removed. `false` if a member with that id
            ///   does not exist.

            delete: function (id, changes) {

                if (this.hasOwn(id)) {

                    this.existing.splice(this.existing.indexOf(id), 1);

                    if (changes) {

                        this.makeOwn("changes");

                        var addedIndex = this.changes.added ?
                            this.changes.added.indexOf(id) : -1;

                        if (addedIndex < 0) {
                            this.changes.removed = this.changes.removed || [];
                            this.changes.removed.push(id);
                        } else {
                            this.changes.added.splice(addedIndex, 1);
                        }

                        if (this.container && this.containerMember) {
                            this.container.change(this.containerMember);
                        }

                    }

                    return true;
                }

                return false;
            },

            /// Record that a member has changed.
            /// 
            /// @param {string|number|boolean|null} id
            ///   The member's unique id.
            /// 
            /// @returns {Boolean}
            ///   `true` if the change was successfully recorded. `false` if a member with that id
            ///   does not exist.

            change: function (id) {

                if (this.hasOwn(id)) {

                    this.makeOwn("changes");

                    var addedIndex = this.changes.added ?
                        this.changes.added.indexOf(id) : -1;

                    var changedIndex = this.changes.changed ?
                        this.changes.changed.indexOf(id) : -1;

                    if (addedIndex < 0 && changedIndex < 0) {
                        this.changes.changed = this.changes.changed || [];
                        this.changes.changed.push(id);
                    }

                    if (this.container && this.containerMember) {
                        this.container.change(this.containerMember);
                    }

                    return true;
                }

                return false;
            },

            /// Determine if a node has a member with the given id.
            /// 
            /// `has` is the same as `hasOwn` for `indexedCollectionPrototype` since index-based
            /// collections don't automatically inherit from their prototypes.
            /// 
            /// @param {string|number|boolean|null} id
            ///   The member's unique id.
            /// 
            /// @returns {Boolean}

            has: function (id) {
                return this.hasOwn(id);
            },

            /// Determine if a node has a member with the given id. The node's prototypes are not
            /// considered.
            /// 
            /// @param {string|number|boolean|null} id
            ///   The member's unique id.
            /// 
            /// @returns {Boolean}

            hasOwn: function (id) {
                return this.existing ? this.existing.indexOf(id) >= 0 : false;
            },

            /// Hoist a field from a prototype to the collection in preparation for making local
            /// changes.
            /// 
            /// If the field in the prototype is an object, create a new object with that field as
            /// its prototype. If the field in the prototype is an array, clone the field since
            /// arrays can't readily serve as prototypes for other arrays. In other cases, copy the
            /// field from the prototype. Only objects, arrays and primitive values are supported.
            /// 
            /// @param {String} fieldName
            ///   The name of a field to hoist from the collection's prototype.

            makeOwn: function (fieldName) {

                if (!this.hasOwnProperty(fieldName)) {

                    if (this[fieldName] instanceof Array) {
                        this[fieldName] = this[fieldName].slice(); // clone arrays
                    } else if (typeof this[fieldName] === "object" && this[fieldName] !== null) {
                        this[fieldName] = Object.create(this[fieldName]); // inherit from objects
                    } else {
                        this[fieldName] = this[fieldName]; // copy primitives
                    }

                }

            },

            /// IDs of the members defined in this collection.
            /// 
            /// `existing` is an ordered list of IDs, which much be unique within the collection.
            /// The IDs retain the order in which they were originally added.
            /// 
            /// For each collection, `existing` is the authoritative list of the node's members. Use
            /// `collection.hasOwn( memberID )` to determine if the collection contains a member
            /// with that id. Unlike `keyedCollectionPrototype` collections,
            /// `indexedCollectionPrototype` collections aren't connected in parallel with their
            /// containers' prototype chains.

            existing: [
                // id,
                // id,
                // ...
            ],

            /// The change list for members in this collection.
            /// 
            /// For patchable nodes, `changes` records the members that have been added, removed, or
            /// changed since the node was first initialized. Changes are recorded in separate
            /// `added`, `removed`, and `changed` arrays, respectively. The `added` array retains
            /// the order in which the members were added. Although `removed` and `changed` are also
            /// arrays, the order of removals and changes is not significant.
            /// 
            /// `changes` is not created in the collection until the first change occurs. Only the
            /// change is recorded here. The state behind the change is retrieved from the drivers
            /// when needed.

            changes: {
                // added: [ id, ... ],
                // removed: [ id, ... ],
                // changed: [ id, ... ],
            },

            /// The parent collection if this collection is a member of another. Changes applied to
            /// members of this collection will call `container.change( containerMember )` to also
            /// set the change flag for the containing member.
            /// 
            /// For example, members of the `node.events` collection contain listener collections at
            /// `node.events.existing[name].listeners`. Each listener collection knows its event
            /// name and points back to `node.events`. Changing a listener will call
            /// `node.events.change( name )` to mark the event as changed.

            container: undefined,

            /// This collection's name in the parent if this collection is a member of another
            /// collection. Changes to members of this collection will mark that member changed in
            /// the containing collection.

            containerMember: undefined,

        }

        // Prototype for the `events` collection in the `nodes` objects.

        this.eventCollectionPrototype = Object.create(self.keyedCollectionPrototype, {

            create: {
                value: function (name, changes, parameters) {
                    var value = parameters ? {
                        parameters: parameters.slice(), // clone
                    } : {};

                    value.listeners = Object.create(self.indexedCollectionPrototype, {
                        container: self.enumerable(this),
                        containerMember: self.enumerable(name),
                    });

                    return self.keyedCollectionPrototype.create.call(this, name, changes, value);
                }

            },

        })

        /// The application's nodes, indexed by ID.
        /// 
        /// The kernel defines an application as:
        /// 
        ///   * A tree of nodes,
        ///   * Extending prototypes and implementing behaviors,
        ///   * Publishing properties, and
        ///   * Communicating using methods and events.
        /// 
        /// This definition is as abstract as possible to avoid imposing unnecessary policy on the
        /// application. The concrete realization of these concepts lives in the hearts and minds of
        /// the drivers configured for the application. `nodes` contains the kernel's authoritative
        /// data about this arrangement.
        /// 
        /// @name module:vwf~nodes

        // Note: this is a first step towards moving authoritative data out of the vwf/model/object
        // and vwf/model/javascript drivers and removing the kernel's dependency on them as special
        // cases. Only `nodes.existing[id].properties` is currently implemented this way.

        this.nodes = this.private.nodes = {

            /// Register a node as it is created.
            /// 
            /// @param {ID} nodeID
            ///   The ID assigned to the new node. The node will be indexed in `nodes` by this ID.
            /// @param {ID} prototypeID
            ///   The ID of the node's prototype, or `undefined` if this is the proto-prototype,
            ///   `node.vwf`.
            /// @param {ID[]} behaviorIDs
            ///   An array of IDs of the node's behaviors. `behaviorIDs` should be an empty array if
            ///   the node doesn't have any behaviors.
            /// @param {String} nodeURI
            ///   The node's URI. `nodeURI` should be the component URI if this is the root node of
            ///   a component loaded from a URI, and undefined in all other cases.
            /// @param {String} nodeName
            ///   The node's name.
            /// @param {ID} parentID
            ///   The ID of the node's parent, or `undefined` if this is the application root node
            ///   or another global, top-level node.
            /// 
            /// @returns {Object} 
            ///   The kernel `node` object if the node was successfully added. `undefined` if a node
            ///   identified by `nodeID` already exists.

            create: function (nodeID, prototypeID, behaviorIDs, nodeURI, nodeName, parentID) {

                // if ( ! this.existing[nodeID] ) {

                let selfNode = this;
                var prototypeNode = behaviorIDs.reduce(function (prototypeNode, behaviorID) {
                    return selfNode.proxy(prototypeNode, selfNode.existing[behaviorID]);
                }, this.existing[prototypeID]);

                // Look up the parent.

                var parentNode = this.existing[parentID];

                // If this is the global root of a new tree, add it to the `globals` set.

                if (!parentNode) {
                    this.globals[nodeID] = undefined;
                }

                //FIX!!!
                // if (parentNode && Object.keys(parentNode.childsDeleted).includes(nodeName))
                //     delete parentNode.childsDeleted[nodeName]

                // Add the node to the registry.

                return this.existing[nodeID] = {

                    // id: ...,

                    // Inheritance. -- not implemented here yet; still using vwf/model/object

                    // prototype: ...,
                    // behaviors: [],

                    // Intrinsic state. -- not implemented here yet.

                    // source: ...,
                    // type: ...,

                    uri: nodeURI,
                    name: nodeName,

                    // Internal state. The change flags are omitted until needed. -- not implemented here yet; still using vwf/model/object

                    // sequence: ...,
                    // sequenceChanged: true / false,

                    // prng: ...,
                    // prngChanged: true / false,

                    // Tree. -- not implemented here yet; still using vwf/model/object

                    // parent: ...,
                    // children: [],

                    // Property, Method and Event members defined on the node.

                    properties: Object.create(self.keyedCollectionPrototype, {
                        existing: self.enumerable(Object.create(prototypeNode ?
                            prototypeNode.properties.existing : null)),
                    }),

                    methods: Object.create(self.keyedCollectionPrototype, {
                        existing: self.enumerable(Object.create(prototypeNode ?
                            prototypeNode.methods.existing : null)),
                    }),

                    events: Object.create(self.eventCollectionPrototype, {
                        existing: self.enumerable(Object.create(prototypeNode ?
                            prototypeNode.events.existing : null)),
                    }),

                    // Is this node patchable? Nodes are patchable if they were loaded from a
                    // component.

                    patchable: !!(nodeURI ||
                        parentNode && !parentNode.initialized && parentNode.patchable),

                    // Has this node completed initialization? For applications, visibility to
                    // ancestors from uninitialized nodes is blocked. Change tracking starts
                    // after initialization.

                    initialized: false,

                    childsDeleted: {}

                };

                // } else {

                //     return undefined;

                // }

            },

            /// Record that a node has initialized.

            initialize: function (nodeID) {

                if (this.existing[nodeID]) {

                    this.existing[nodeID].initialized = true;

                    return true;
                }

                return false;
            },

            /// Unregister a node as it is deleted.

            delete: function (nodeID, parentID) {

                if (this.existing[nodeID] && this.existing[parentID]) {

                    this.existing[parentID].childsDeleted[this.existing[nodeID].name] = nodeID;

                    delete this.existing[nodeID];
                    delete this.globals[nodeID];

                    return true;
                }

                return false;
            },

            /// Create a proxy node in the form of the nodes created by `nodes.create` to represent
            /// a behavior node in another node's prototype chain. The `existing` objects of the
            /// proxy's collections link to the prototype collection's `existing` objects, just as
            /// with a regular prototype. The proxy's members delegate to the corresponding members
            /// in the behavior.

            proxy: function (prototypeNode, behaviorNode) {

                return {

                    properties: {
                        existing: Object.create(
                            prototypeNode ? prototypeNode.properties.existing : null,
                            propertyDescriptorsFor(behaviorNode.properties.existing)
                        ),
                    },

                    methods: {
                        existing: Object.create(
                            prototypeNode ? prototypeNode.methods.existing : null,
                            propertyDescriptorsFor(behaviorNode.methods.existing)
                        ),
                    },

                    events: {
                        existing: Object.create(
                            prototypeNode ? prototypeNode.events.existing : null,
                            propertyDescriptorsFor(behaviorNode.events.existing)
                        ),
                    },

                };

                /// Return an `Object.create` properties object for a proxy object for the provided
                /// collection's `existing` object.

                function propertyDescriptorsFor(collectionExisting) {

                    return Object.keys(collectionExisting).reduce(

                        function (propertiesObject, memberName) {

                            propertiesObject[memberName] = {
                                get: function () {
                                    return collectionExisting[memberName]
                                },
                                enumerable: true,
                            };

                            return propertiesObject;
                        },

                        {}

                    );

                }

            },

            /// Registry of all nodes, indexed by ID. Each is an object created by `nodes.create`.

            existing: {

                // id: {
                //     id: ...,
                //     uri: ...,
                //     name: ...,
                //     ...
                // }

            },

            /// Global root nodes. Each of these is the root of a tree.
            /// 
            /// The `globals` object is a set: the keys are the data, and only existence on the
            /// object is significant.

            globals: {
                // id: undefined,
            }

        }

    }

    // == Public functions =====================================================================

    // -- loadConfiguration ---------------------------------------------------------------------------

    // The main page only needs to call vwf.loadConfiguration() to launch the application. Use
    // require.ready() or jQuery(document).ready() to call loadConfiguration() once the page has
    // loaded. loadConfiguration() accepts three parameters.
    // 
    // A component specification identifies the application to be loaded. modelInitializers and 
    // viewInitializers identify the model and view libraries that were parsed out of the URL that 
    // should be attached to the simulation. Each is specified as an object with each library 
    // name as a property of the object with any arguments as the value of the property.
    // Arguments may be specified as an array [1], as a single value if there is only one [2], or as 
    // undefined if there are none[3].
    // 
    //     [1] vwf.loadConfiguration( ..., { "vwf/model/glge": [ "#scene, "second param" ] }, { ... } )
    //     [2] vwf.loadConfiguration( ..., { "vwf/model/glge": "#scene" }, { ... } )
    //     [3] vwf.loadConfiguration( ..., { "vwf/model/javascript": undefined }, { ... } )

    loadConfiguration(app, userLib, cb

        /* [ componentURI|componentObject ] { modelInitializers }
                    { viewInitializers } */
    ) {
        let self = this;

        let applicationLoad = app;
        let userLibraries = userLib || {};

        var applicationConfig = {};
        let callback = cb;

        var initializers = {
            model: [
                {
                    library: "/core/vwf/model/ohm",
                    active: true
                },
                {
                    library: "/core/vwf/model/javascript",
                    active: true
                },
                {
                    library: "/core/vwf/model/object",
                    active: true
                }

            ],
            view: [

                {
                    library: "/core/vwf/view/ohm",
                    active: true
                },

                {
                    library: "/core/vwf/view/document",
                    active: true
                },


            ]
        };
        //mapLibraryName(requireArray);
        mapLibraryName(initializers["model"]);
        mapLibraryName(initializers["view"]);

        function mapLibraryName(array) {
            for (var i = 0; i < array.length; i++) {
                array[array[i].library] = array[i];
            }
        }

        function getActiveLibraries(libraryList, includeParameters) {
            var activeLibraryList = [];
            for (var i = 0; i < libraryList.length; i++) {
                if (libraryList[i].active) {
                    if (includeParameters) {
                        var activeLibrary = {};
                        activeLibrary[libraryList[i].library] = libraryList[i].parameters;
                        activeLibraryList.push(activeLibrary);
                    } else {
                        activeLibraryList.push(libraryList[i].library);
                    }
                }
            }
            return activeLibraryList;
        }


        // let confPromise = new Promise((resolve, reject) => {
        //     resolve(this.driverConfiguration);
        // });

        let configLibraries = this.driverConfiguration;

        if (configLibraries && typeof configLibraries == "object") {
            if (typeof configLibraries.configuration == "object") {
                applicationConfig = configLibraries.configuration;
            }
            Object.keys(configLibraries).forEach(function (libraryType) {
                if (libraryType == 'info' && configLibraries[libraryType]["title"]) {
                    //jQuery('title').html(configLibraries[libraryType]["title"]);
                    document.querySelector('title').innerHTML = configLibraries[libraryType]["title"]
                }
                if (!userLibraries[libraryType]) {
                    userLibraries[libraryType] = {};
                }
                // Merge libraries from config file and URL together. Check for incompatible
                // libraries, and disable them.
                Object.keys(configLibraries[libraryType]).forEach(function (libraryName) {
                    var disabled = false;
                    if (!disabled) {
                        if (userLibraries[libraryType][libraryName] == undefined) {
                            userLibraries[libraryType][libraryName] = configLibraries[libraryType][libraryName];
                        } else if (typeof userLibraries[libraryType][libraryName] == "object" && typeof configLibraries[libraryType][libraryName] == "object") {
                            userLibraries[libraryType][libraryName] = Object.assign({}, configLibraries[libraryType][libraryName], userLibraries[libraryType][libraryName]);
                        }
                    }
                });
            });
        }


        Object.keys(userLibraries).forEach(function (libraryType) {
            if (initializers[libraryType]) {
                Object.keys(userLibraries[libraryType]).forEach(function (libraryName) {
                    //if (requireArray[libraryName]) {
                    // requireArray[libraryName].active = true;

                    if (!initializers[libraryType][libraryName]) {

                        initializers[libraryType].unshift({ 'library': libraryName });
                        initializers[libraryType][libraryName] = initializers[libraryType][0];

                    }
                    initializers[libraryType][libraryName].active = true;
                    if (userLibraries[libraryType][libraryName] && userLibraries[libraryType][libraryName] != "") {
                        if (typeof initializers[libraryType][libraryName].parameters == "object") {

                            initializers[libraryType][libraryName].parameters = Object.assign({}, initializers[libraryType][libraryName].parameters, userLibraries[libraryType][libraryName]);

                        } else {
                            initializers[libraryType][libraryName].parameters = userLibraries[libraryType][libraryName];
                        }
                    }
                });
            }
        })


        // Load default renderer if no other librarys specified
        // if (Object.keys(userLibraries["model"]).length == 0 && Object.keys(userLibraries["view"]).length == 0) {
        //     // requireArray["vwf/model/threejs"].active = true;
        // }

        // With the scripts loaded, we must initialize the framework. vwf.initialize()
        // accepts three parameters: a world specification, model configuration parameters,
        // and view configuration parameters.

        self.initialize(self.applicationLoad, getActiveLibraries(initializers["model"], true), getActiveLibraries(initializers["view"], true), callback);



    }



    // -- initialize ---------------------------------------------------------------------------

    /// The main page only needs to call vwf.initialize() to launch the application. Use
    /// require.ready() or jQuery(document).ready() to call initialize() once the page has
    /// loaded. initialize() accepts three parameters.
    /// 
    /// A component specification identifies the application to be loaded. If a URI is provided,
    /// the specification is loaded from there [1]. Alternately, a JavaScript object literal
    /// containing the specfication may be provided [2]. Since a component can extend and
    /// specialize a prototype, using a simple object literal allows existing component to be
    /// configured for special uses [3].
    /// 
    ///     [1] vwf.initialize( "http://vwf.example.com/applications/sample12345", ... )
    ///
    ///     [2] vwf.initialize( { source: "model.dae", type: "model/vnd.collada+xml",
    ///             properties: { "p1": ... }, ... }, ... )
    ///
    ///     [3] vwf.initialize( { extends: "http://vwf.example.com/applications/sample12345",
    ///             source: "alternate-model.dae", type: "model/vnd.collada+xml" }, ... )
    /// 
    /// modelInitializers and viewInitializers identify the model and view modules that should be
    /// attached to the simulation. Each is specified as an array of objects that map the name of
    /// a model or view to construct to the set of arguments to pass to its constructor. Modules
    /// without parameters may be specified as a string [4]. Arguments may be specified as an
    /// array [5], or as a single value if there is only one [6].
    /// 
    ///     [4] vwf.initialize( ..., [ "vwf/model/javascript" ], [ ... ] )
    ///     [5] vwf.initialize( ..., [ { "vwf/model/glge": [ "#scene, "second param" ] } ], [ ... ] )
    ///     [6] vwf.initialize( ..., [ { "vwf/model/glge": "#scene" } ], [ ... ] )
    /// 
    /// @name module:vwf.initialize

    async initialize(
        /* [ componentURI|componentObject ] [ modelInitializers ]
                   [ viewInitializers ] */
    ) {

        let self = this;

        var args = Array.prototype.slice.call(arguments);
        //var application;

        // Load the runtime configuration. We start with the factory defaults. The reflector may
        // provide additional settings when we connect.

        //this.configuration = require("vwf/configuration").active; // "active" updates in place and changes don't invalidate the reference

        // Load the kernel utilities.

        //this.kutility =  new KUtility //require("vwf/kernel/utility");

        // Create the logger.

        //this.logger = require("logger").for("vwf", this); // TODO: for( "vwf", ... ), and update existing calls

        // Get the jQuery reference. This also happens in `loadConfiguration`, but the tests
        // initialize using `initialize` and don't call `loadConfiguration` first.

        //  jQuery = require("jquery");

        // Parse the function parameters. If the first parameter is not an array, then treat it
        // as the application specification. Otherwise, fall back to the "application" parameter
        // in the query string.

        if (typeof args[0] != "object" || !(args[0] instanceof Array)) {
            this.applicationLoad = args.shift();
        }

        // Shift off the parameter containing the model list and initializer arguments.

        var modelInitializers = args.shift() || [];

        // Shift off the parameter containing the view list and initializer arguments.

        var viewInitializers = args.shift() || [];

        var callback = args.shift();
        var compatibilityStatus = {
            compatible: true,
            errors: {}
        };

        // Create the model interface to the kernel. Models can make direct calls that execute
        // immediately or future calls that are placed on the queue and executed when removed.

        let modelKernel = new ModelKernel({
            id: "vwf/kernel/model"
        }).factory();
        this.models.kernel = modelKernel.create(vwf);

        //this.models.kernel = require("vwf/kernel/model").create(vwf);

        // Create and attach each configured model.

        for (let modelInitializer of modelInitializers) {
            //modelInitializers.forEach(function (modelInitializer) {

            // Skip falsy values to allow initializers to be conditionally included by the
            // loader.

            if (modelInitializer) {

                // Accept either { "vwf/model/name": [ arguments] } or "vwf/model/name".

                if (typeof modelInitializer == "object" && modelInitializer != null) {
                    var modelName = Object.keys(modelInitializer)[0];
                    var modelArguments = modelInitializer[modelName];
                } else {
                    var modelName = modelInitializer;
                    var modelArguments = undefined;
                }

                let log = new Log({
                    id: "vwf/model/stage/log"
                }).factory();

                //
                var modelMod = undefined;
                await import(modelName + '.js').then(m => {
                    modelMod = (new m.default({
                        id: modelName
                    }).factory())
                });


                var model = modelMod.create(
                    this.models.kernel, // model's kernel access
                    [log],
                    //[require("vwf/model/stage/log")], // stages between the kernel and model
                    {}, // state shared with a paired view
                    [].concat(modelArguments || []) // arguments for initialize()
                );


                if (model) {
                    this.models.push(model);
                    this.models[modelName] = model; // also index by id  // TODO: this won't work if multiple model instances are allowed

                    if (modelName == "/core/vwf/model/javascript") { // TODO: need a formal way to follow prototype chain from vwf.js; this is peeking inside of vwf-model-javascript
                        this.models.javascript = model;
                        while (this.models.javascript.model) this.models.javascript = this.models.javascript.model;
                    }

                    if (modelName == "/core/vwf/model/object") { // TODO: this is peeking inside of vwf-model-object
                        this.models.object = model;
                        while (this.models.object.model) this.models.object = this.models.object.model;
                    }

                    if (model.model.compatibilityStatus) {
                        if (!model.model.compatibilityStatus.compatible) {
                            compatibilityStatus.compatible = false;
                            Object.assign(compatibilityStatus.errors, model.model.compatibilityStatus.errors);
                            //jQuery.extend(compatibilityStatus.errors, model.model.compatibilityStatus.errors);
                        }
                    }
                }

            }

        }
        //, this);

        // Create the view interface to the kernel. Views can only make replicated calls which
        // bounce off the reflection server, are placed on the queue when received, and executed
        // when removed.

        let viewKernel = new ViewKernel({
            id: "vwf/kernel/view"
        }).factory();

        this.views.kernel = viewKernel.create(vwf);

        //this.views.kernel = require("vwf/kernel/view").create(vwf);

        // Create and attach each configured view.

        for (let viewInitializer of viewInitializers) {
            //viewInitializers.forEach(function (viewInitializer) {

            // Skip falsy values to allow initializers to be conditionally included by the
            // loader.

            if (viewInitializer) {

                // Accept either { "vwf/view/name": [ arguments] } or "vwf/view/name".

                if (typeof viewInitializer == "object" && viewInitializer != null) {
                    var viewName = Object.keys(viewInitializer)[0];
                    var viewArguments = viewInitializer[viewName];
                } else {
                    var viewName = viewInitializer;
                    var viewArguments = undefined;
                }

                // if (!viewName.match("^vwf/view/")) { // old way

                //     var view = this.modules[viewName];

                //     if (view) {
                //         var instance = new view();
                //         instance.state = this.models.actual["vwf/model/" + viewName] && this.models.actual["vwf/model/" + viewName].state || {}; // state shared with a paired model
                //         view.apply(instance, [vwf].concat(viewArguments || []));
                //         this.views.push(instance);
                //         this.views[viewName] = instance; // also index by id  // TODO: this won't work if multiple view instances are allowed

                //         if (view.compatibilityStatus) {
                //             if (!view.compatibilityStatus.compatible) {
                //                 compatibilityStatus.compatible = false;
                //                 Object.assign(compatibilityStatus.errors, view.compatibilityStatus.errors);
                //                 // jQuery.extend(compatibilityStatus.errors, view.compatibilityStatus.errors);
                //             }
                //         }
                //     }

                // } else { 
                // new way

                var modelPeer = this.models.actual[viewName.replace("view/", "model/")]; // TODO: this.model.actual() is kind of heavy, but it's probably OK to use just a few times here at start-up


                var viewMod = undefined;
                await import(viewName + '.js').then(m => {
                    viewMod = (new m.default({
                        id: viewName
                    }).factory())
                })

                var view = viewMod.create(
                    this.views.kernel, // view's kernel access
                    [], // stages between the kernel and view
                    modelPeer && modelPeer.state || {}, // state shared with a paired model
                    [].concat(viewArguments || []) // arguments for initialize()
                );



                if (view) {
                    this.views.push(view);
                    this.views[viewName] = view; // also index by id  // TODO: this won't work if multiple view instances are allowed

                    if (view.compatibilityStatus) {
                        if (!view.compatibilityStatus.compatible) {
                            compatibilityStatus.compatible = false;
                            Object.assign(compatibilityStatus.errors, view.compatibilityStatus.errors);
                            // jQuery.extend(compatibilityStatus.errors, view.compatibilityStatus.errors);
                        }
                    }
                }

                //}

            }

        }
        //, this);


        if (callback) {
            callback(compatibilityStatus);
        }

        //await _app.getApplicationState();
        await _app.getApplicationState()
            .then(res => {
                return self.chooseConnection(res)
            })
            .then(res => {
                self.ready(self.application, res)
            })

    }

    // -- ready --------------------------------------------------------------------------------

    /// @name module:vwf.ready

    ready(component_uri_or_json_or_object, path) {

        // Connect to the reflector. This implementation uses the socket.io library, which
        // communicates using a channel back to the server that provided the client documents.

        if (this.isLuminary) {
            //Use Luminary for connection

            this.namespace_ = this.luminary.namespace; //this.helpers.GetNamespace(path.path); //.split(".").join("_");
            this.moniker_ = this.luminary.clientID;
            console.log('namespace: ' + this.namespace_, ' for client: ' + this.moniker_);

            //let heartbeat = _LCSDB.get('server').get('heartbeat'); 
            var heartbeat = _lum.get(this.namespace_).get('heartbeat'); //_LCSDB.get(vwf.namespace_).get('heartbeat');

            if (this.isLuminaryGlobalHB && this.luminaryGlobalHBPath) {
                let hbPath = this.luminaryGlobalHBPath.split('/');
                var heartbeat = _LCSDB;
                hbPath.forEach(el => {
                    heartbeat = heartbeat.get(el);
                })
            }

            this.luminary.subscribeOnHeartbeat(heartbeat);
            this.luminary.subscribeOnMessages();


        } else {
            //Use Reflector for connection

            this.reflectorClient.connect(component_uri_or_json_or_object, path);

        }

    }

    // -- log ----------------------------------------------------------------------------------

    /// Send a log message to the reflector.
    /// 
    /// @name module:vwf.log

    log() {

        this.respond(undefined, "log", undefined, undefined, arguments);

    }


    // -- setState -----------------------------------------------------------------------------

    /// setState may complete asynchronously due to its dependence on createNode. To prevent
    /// actions from executing out of order, queue processing must be suspended while setState is
    /// in progress. createNode suspends the queue when necessary, but additional calls to
    /// suspend and resume the queue may be needed if other async operations are added.
    /// 
    /// @name module:vwf.setState
    /// 
    /// @see {@link module:vwf/api/kernel.setState}

    setState(appState, callback_async /* () */) {
        let self = this;

        this.logger.debuggx("setState"); // TODO: loggableState

        // Set the runtime configuration.

        var applicationState = appState;

        if (applicationState.init) {
            applicationState = JSON.parse(localStorage.getItem('lcs_app')).saveObject
        }

        if (applicationState.configuration) {
            this.configuration = applicationState.configuration;
            //require("vwf/configuration").instance = applicationState.configuration;
        }

        // Update the internal kernel state.

        if (applicationState.kernel) {
            if (applicationState.kernel.time !== undefined) self.virtualTime.now = applicationState.kernel.time;
        }

        // Create or update global nodes and their descendants.

        var nodes = applicationState.nodes || [];
        var annotations = applicationState.annotations || {};

        var nodeIndex = 0;

        async.forEachSeries(nodes, function (nodeComponent, each_callback_async /* ( err ) */) {

            // Look up a possible annotation for this node. For backward compatibility, if the
            // state has exactly one node and doesn't contain an annotations object, assume the
            // node is the application.

            var nodeAnnotation = self.nodes.length > 1 || applicationState.annotations ?
                annotations[nodeIndex] : "application";

            self.createNode(nodeComponent, nodeAnnotation, function (nodeID) /* async */ {
                each_callback_async(undefined);
            });

            nodeIndex++;

        }, function (err) /* async */ {

            // Clear the message queue, except for reflector messages that arrived after the
            // current action.

            self.virtualTime.filterQueue();

            // Set the queue time and add the incoming items to the queue.

            if (applicationState.queue) {
                self.virtualTime.time = applicationState.queue.time;
                self.virtualTime.insert(applicationState.queue.queue || []);
            }

            callback_async && callback_async();

        });

        this.logger.debugu();
    };

    // -- getState -----------------------------------------------------------------------------

    /// @name module:vwf.getState
    /// 
    /// @see {@link module:vwf/api/kernel.getState}

    getState(full, normalize) {

        let self = this;
        this.logger.debuggx("getState", full, normalize);

        // Get the application nodes and queue.

        var applicationState = {

            // Runtime configuration.

            configuration: self.configuration, //require("vwf/configuration").active,

            // Internal kernel state.

            kernel: {
                time: self.virtualTime.now,
            },

            // Global node and descendant deltas.

            nodes: [ // TODO: all global objects
                this.getNode("proxy/clients.vwf", full),
                this.getNode(this.application(), full),
            ],

            // `createNode` annotations, keyed by `nodes` indexes.

            annotations: {
                1: "application",
            },

            // Message queue.

            queue: self.virtualTime.stateQueue


        };

        // Normalize for consistency.

        if (normalize) {
            applicationState = self.utility.transform(
                applicationState, self.utility.transforms.hash);
        }

        this.logger.debugu();

        return applicationState;
    };

    // -- hashState ----------------------------------------------------------------------------

    /// @name module:vwf.hashState
    /// 
    /// @see {@link module:vwf/api/kernel.hashState}

    hashState() {

        this.logger.debuggx("hashState");

        var applicationState = this.getState(true, true);

        // Hash the nodes.

        var hashn = this.hashNode(applicationState.nodes[0]); // TODO: all global objects

        // Hash the queue.

        var hashq = "q" + Crypto.MD5(JSON.stringify(applicationState.queue)).toString().substring(0, 16);

        // Hash the other kernel properties.

        var hashk = "k" + Crypto.MD5(JSON.stringify(applicationState.kernel)).toString().substring(0, 16);

        this.logger.debugu();

        // Generate the combined hash.

        return hashn + ":" + hashq + ":" + hashk;
    }




    // -- createNode ---------------------------------------------------------------------------

    /// Create a node from a component specification. Construction may require loading data from
    /// multiple remote documents. This function returns before construction is complete. A
    /// callback is invoked once the node has fully loaded.
    /// 
    /// A simple node consists of a set of properties, methods and events, but a node may
    /// specialize a prototype component and may also contain multiple child nodes, any of which
    /// may specialize a prototype component and contain child nodes, etc. So components cover a
    /// vast range of complexity. The application definition for the overall simulation is a
    /// single component instance.
    /// 
    /// A node is a component instance--a single, anonymous specialization of its component.
    /// Nodes specialize components in the same way that any component may specialize a prototype
    /// component. The prototype component is made available as a base, then new or modified
    /// properties, methods, events, child nodes and scripts are attached to modify the base
    /// implemenation.
    /// 
    /// To create a node, we first make the prototoype available by loading it (if it has not
    /// already been loaded). This is a recursive call to createNode() with the prototype
    /// specification. Then we add new, and modify existing, properties, methods, and events
    /// according to the component specification. Then we load and add any children, again
    /// recursively calling createNode() for each. Finally, we attach any new scripts and invoke
    /// an initialization function.
    /// 
    /// createNode may complete asynchronously due to its dependence on setNode, createChild and
    /// loadComponent. To prevent actions from executing out of order, queue processing must be
    /// suspended while createNode is in progress. setNode, createChild and loadComponent suspend
    /// the queue when necessary, but additional calls to suspend and resume the queue may be
    /// needed if other async operations are added.
    /// 
    /// @name module:vwf.createNode
    /// 
    /// @see {@link module:vwf/api/kernel.createNode}

    createNode(nodeComponent, nodeAnnotation, baseURI, callback_async /* ( nodeID ) */) {

        let self = this;

        // Interpret `createNode( nodeComponent, callback )` as
        // `createNode( nodeComponent, undefined, undefined, callback )` and
        // `createNode( nodeComponent, nodeAnnotation, callback )` as
        // `createNode( nodeComponent, nodeAnnotation, undefined, callback )`. `nodeAnnotation`
        // was added in 0.6.12, and `baseURI` was added in 0.6.25.

        if (typeof nodeAnnotation == "function" || nodeAnnotation instanceof Function) {
            callback_async = nodeAnnotation;
            baseURI = undefined;
            nodeAnnotation = undefined;
        } else if (typeof baseURI == "function" || baseURI instanceof Function) {
            callback_async = baseURI;
            baseURI = undefined;
        }

        this.logger.debuggx("createNode", function () {
            return [JSON.stringify(self.loggableComponent(nodeComponent)), nodeAnnotation];
        });

        var nodePatch;

        if (self.componentIsDescriptor(nodeComponent) && nodeComponent.patches) {
            nodePatch = nodeComponent;
            nodeComponent = nodeComponent.patches; // TODO: possible sync errors if the patched node is a URI component and the kernel state (time, random) is different from when the node was created on the originating client
        }

        // nodeComponent may be a URI, a descriptor, or an ID. While being created, it will
        // transform from a URI to a descriptor to an ID (depending on its starting state).
        // nodeURI, nodeDescriptor, and nodeID capture the intermediate states.

        var nodeURI, nodeDescriptor, nodeID;

        async.series([

            // If `nodeComponent` is a URI, load the descriptor. `nodeComponent` may be a URI, a
            // descriptor or an ID here.

            function (series_callback_async /* ( err, results ) */) {

                if (self.componentIsURI(nodeComponent)) { // URI  // TODO: allow non-vwf URIs (models, images, etc.) to pass through to stage 2 and pass directly to createChild()

                    // Resolve relative URIs, but leave host-relative, locally-absolute
                    // references intact.

                    nodeURI = nodeComponent
                    //nodeComponent[0] == "/" ? nodeComponent : require( "vwf/utility" ).resolveURI( nodeComponent, baseURI );

                    // Load the document if we haven't seen this URI yet. Mark the components
                    // list to indicate that this component is loading.

                    if (!self.components[nodeURI]) { // uri is not loading (Array) or is loaded (id)

                        self.components[nodeURI] = []; // [] => array of callbacks while loading => true

                        self.loadComponent(nodeURI, undefined, function (nodeDescriptor) /* async */ {
                            nodeComponent = nodeDescriptor;
                            series_callback_async(undefined, undefined);
                        }, function (errorMessage) {
                            nodeComponent = undefined;
                            series_callback_async(errorMessage, undefined);
                        });

                        // If we've seen this URI, but it is still loading, just add our callback to
                        // the list. The original load's completion will call our callback too.

                    } else if (self.components[nodeURI] instanceof Array) { // uri is loading

                        callback_async && self.components[nodeURI].push(callback_async); // TODO: is this leaving a series callback hanging if we don't call series_callback_async?

                        // If this URI has already loaded, skip to the end and call the callback
                        // with the ID.

                    } else { // uri is loaded

                        if (nodePatch) {
                            self.setNode(self.components[nodeURI], nodePatch, function (nodeID) /* async */ {
                                callback_async && callback_async(self.components[nodeURI]); // TODO: is this leaving a series callback hanging if we don't call series_callback_async?
                            });
                        } else {
                            callback_async && callback_async(self.components[nodeURI]); // TODO: is this leaving a series callback hanging if we don't call series_callback_async?
                        }

                    }

                } else { // descriptor, ID or error
                    series_callback_async(undefined, undefined);
                }

            },

            // Rudimentary support for `{ includes: prototype }`, which absorbs a prototype
            // descriptor into the node descriptor before creating the node.

            // Notes:
            // 
            //   - Only supports one level, so `{ includes: prototype }` won't work if the
            //     prototype also contains a `includes` directive).
            //   - Only works with prototype URIs, so `{ includes: { ... descriptor ... } }`
            //     won't work.
            //   - Loads the prototype on each reference, so unlike real prototypes, multiple
            //     references to the same prototype cause multiple network loads.
            // 
            // Also see the `mergeDescriptors` limitations.

            function (series_callback_async /* ( err, results ) */) {

                if (self.componentIsDescriptor(nodeComponent) && nodeComponent.includes && self.componentIsURI(nodeComponent.includes)) { // TODO: for "includes:", accept an already-loaded component (which componentIsURI exludes) since the descriptor will be loaded again

                    var prototypeURI = nodeComponent.includes //require( "vwf/utility" ).resolveURI( nodeComponent.includes, nodeURI || baseURI );

                    self.loadComponent(prototypeURI, undefined, function (prototypeDescriptor) /* async */ {
                        prototypeDescriptor = self.resolvedDescriptor(prototypeDescriptor, prototypeURI);
                        nodeComponent = self.mergeDescriptors(nodeComponent, prototypeDescriptor); // modifies prototypeDescriptor
                        series_callback_async(undefined, undefined);
                    }, function (errorMessage) {
                        nodeComponent = undefined;
                        series_callback_async(errorMessage, undefined);
                    });

                } else {
                    series_callback_async(undefined, undefined);
                }

            },

            // If `nodeComponent` is a descriptor, construct and get the ID. `nodeComponent` may
            // be a descriptor or an ID here.

            function (series_callback_async /* ( err, results ) */) {

                if (self.componentIsDescriptor(nodeComponent)) { // descriptor  // TODO: allow non-vwf URIs (models, images, etc.) to pass through to stage 2 and pass directly to createChild()

                    nodeDescriptor = nodeComponent;

                    // Create the node as an unnamed child global object.

                    self.createChild(0, nodeAnnotation, nodeDescriptor, nodeURI, function (nodeID) /* async */ {
                        nodeComponent = nodeID;
                        series_callback_async(undefined, undefined);
                    });

                } else { // ID or error
                    series_callback_async(undefined, undefined);
                }

            },

            // nodeComponent is an ID here.

            function (series_callback_async /* ( err, results ) */) {

                if (self.componentIsID(nodeComponent) || self.components[nodeComponent] instanceof Array) { // ID

                    nodeID = nodeComponent;

                    if (nodePatch) {
                        self.setNode(nodeID, nodePatch, function (nodeID) /* async */ {
                            series_callback_async(undefined, undefined);
                        });
                    } else {
                        series_callback_async(undefined, undefined);
                    }

                } else { // error
                    series_callback_async(undefined, undefined); // TODO: error
                }

            },

        ], function (err, results) /* async */ {

            // If this node derived from a URI, save the list of callbacks waiting for
            // completion and update the component list with the ID.

            if (nodeURI) {
                var callbacks_async = self.components[nodeURI];
                self.components[nodeURI] = nodeID;
            }

            // Pass the ID to our callback.

            callback_async && callback_async(nodeID); // TODO: handle error if invalid id

            // Call the other callbacks.

            if (nodeURI) {
                callbacks_async.forEach(function (callback_async) {
                    callback_async && callback_async(nodeID);
                });
            }

        });

        this.logger.debugu();
    }

    // -- deleteNode ---------------------------------------------------------------------------

    /// @name module:vwf.deleteNode
    /// 
    /// @see {@link module:vwf/api/kernel.deleteNode}

    deleteNode(nodeID, replaceFlag) {
        let self = this;

        this.logger.debuggx("deleteNode", nodeID);

        // Send the meta event into the application. We send it before deleting the child so
        // that the child will still be available for review.

        var parentID = this.parent(nodeID);

        if (parentID !== 0) {

            var nodeIndex = this.children(parentID).indexOf(nodeID);

            if (nodeIndex < 0) {
                nodeIndex = undefined;
            }

            if (this.models.kernel.enabled()) {
                this.fireEvent(parentID, ["children", "removed"],
                    [nodeIndex, this.kutility.nodeReference(nodeID)]);
            }

        }

        // Remove the entry in the components list if this was the root of a component loaded
        // from a URI.

        Object.keys(self.components).some(function (nodeURI) { // components: nodeURI => nodeID
            if (self.components[nodeURI] == nodeID) {
                delete self.components[nodeURI];
                return true;
            }
        });

        //Delete childs nodes
        self.children(nodeID).forEach(function (child) {
            self.deleteNode(child);
        });


        // Call deletingNode() on each model. The node is considered deleted after all models
        // have run.

        this.models.forEach(function (model) {
            model.deletingNode && model.deletingNode(nodeID, replaceFlag);
        });

        // Unregister the node.

        this.nodes.delete(nodeID, parentID);

        // Call deletedNode() on each view. The view is being notified that a node has been
        // deleted.

        this.views.forEach(function (view) {
            view.deletedNode && view.deletedNode(nodeID);
        });

        this.logger.debugu();
    }

    // -- setNode ------------------------------------------------------------------------------

    /// setNode may complete asynchronously due to its dependence on createChild. To prevent
    /// actions from executing out of order, queue processing must be suspended while setNode is
    /// in progress. createChild suspends the queue when necessary, but additional calls to
    /// suspend and resume the queue may be needed if other async operations are added.
    /// 
    /// @name module:vwf.setNode
    /// 
    /// @see {@link module:vwf/api/kernel.setNode}

    setNode(nodeID, nodeComponent, callback_async /* ( nodeID ) */) { // TODO: merge with createChild?

        let self = this;
        self.logger.debuggx("setNode", function () {
            return [nodeID, JSON.stringify(self.loggableComponent(nodeComponent))];
        });

        var node = self.nodes.existing[nodeID];

        // Set the internal state.

        self.models.object.internals(nodeID, nodeComponent);

        // Suppress kernel reentry so that we can write the state without coloring from
        // any scripts.

        self.models.kernel.disable();

        // Create the properties, methods, and events. For each item in each set, invoke
        // createProperty(), createMethod(), or createEvent() to create the field. Each
        // delegates to the models and views as above.

        // Properties.

        nodeComponent.properties && Object.keys(nodeComponent.properties).forEach(function (propertyName) { // TODO: setProperties should be adapted like this to be used here
            var propertyValue = nodeComponent.properties[propertyName];

            // Is the property specification directing us to create a new property, or
            // initialize a property already defined on a prototype?

            // Create a new property if the property is not defined on a prototype.
            // Otherwise, initialize the property.

            // if(!node){
            //     console.log(nodeComponent);
            //     return
            // }

            var creating = !node.properties.has(propertyName); // not defined on node or prototype

            // Translate node references in the descriptor's form `{ node: nodeID }` into kernel
            // node references.

            if (self.valueHasAccessors(propertyValue) && propertyValue.node) {
                propertyValue = self.kutility.nodeReference(propertyValue.node);
            }

            // Create or initialize the property.

            if (creating) {
                self.createProperty(nodeID, propertyName, propertyValue);
            } else {
                self.setProperty(nodeID, propertyName, propertyValue);
            } // TODO: delete when propertyValue === null in patch

        });

        // Methods.

        nodeComponent.methods && Object.keys(nodeComponent.methods).forEach(function (methodName) {
            var methodHandler = nodeComponent.methods[methodName];

            var creating = !node.methods.has(methodName); // not defined on node or prototype

            // Create or initialize the method.

            if (creating) {
                self.createMethod(nodeID, methodName, methodHandler.parameters, methodHandler.body);
            } else {
                self.setMethod(nodeID, methodName, methodHandler);
            } // TODO: delete when methodHandler === null in patch

        });

        // Events.

        nodeComponent.events && Object.keys(nodeComponent.events).forEach(function (eventName) {
            var eventDescriptor = nodeComponent.events[eventName];

            var creating = !node.events.has(eventName); // not defined on node or prototype

            // Create or initialize the event.

            if (creating) {
                self.createEvent(nodeID, eventName, eventDescriptor.parameters);
                self.setEvent(nodeID, eventName, eventDescriptor); // set the listeners since `createEvent` can't do it yet
            } else {
                self.setEvent(nodeID, eventName, eventDescriptor);
            } // TODO: delete when eventDescriptor === null in patch

        });

        // Restore kernel reentry.

        self.models.kernel.enable();


        async.series([

            function (series_callback_async /* ( err, results ) */) {

                // Create and attach the children. For each child, call createChild() with the
                // child's component specification. createChild() delegates to the models and
                // views as before.

                async.forEach(Object.keys(nodeComponent.children || {}), function (childName, each_callback_async /* ( err ) */) {

                    var creating = !self.nodeHasOwnChild.call(self, nodeID, childName);
                    if (creating) {
                        self.createChild(nodeID, childName, nodeComponent.children[childName], undefined, function (childID) /* async */ { // TODO: add in original order from nodeComponent.children  // TODO: ensure id matches nodeComponent.children[childName].id  // TODO: propagate childURI + fragment identifier to children of a URI component?
                            each_callback_async(undefined);
                        });
                    } else {
                        self.setNode(nodeComponent.children[childName].id || nodeComponent.children[childName].patches,
                            nodeComponent.children[childName],
                            function (childID) /* async */ {
                                each_callback_async(undefined);
                            });
                    } // TODO: delete when nodeComponent.children[childName] === null in patch
                }, function (err) /* async */ {
                    let deletedProtoNodes = nodeComponent.childrenDeleted;

                    if (deletedProtoNodes) {
                        let childNames = Object.keys(nodeComponent.childrenDeleted)
                        if (childNames) {
                            childNames.forEach(el => {
                                console.log("DELETE CHILD HERE!: ", el);

                                //self.deleteChild(nodeID, el);
                                var indm = false;
                                for (const prop in nodeComponent.children) {
                                    if (nodeComponent.children[prop].properties && nodeComponent.children[prop].properties.displayName) {

                                        if (nodeComponent.children[prop].properties.displayName == el ||
                                            nodeComponent.children[prop].properties.displayName.value == el) {
                                            indm = true;
                                            //console.log('REPLACE: ');
                                            //self.deleteChild(nodeID, el, true);
                                        }

                                    } else {
                                        indm = false;
                                        //self.deleteChild(nodeID, el);
                                    }

                                }
                                if (nodeComponent.children && !nodeComponent.children[el] && indm) {
                                    self.deleteChild(nodeID, el, true)
                                } else {
                                    self.deleteChild(nodeID, el)
                                }

                            });
                        }
                    }
                    series_callback_async(err, undefined);
                });

            },

            function (series_callback_async /* ( err, results ) */) {

                // Attach the scripts. For each script, load the network resource if the script
                // is specified as a URI, then once loaded, call execute() to direct any model
                // that manages scripts of this script's type to evaluate the script where it
                // will perform any immediate actions and retain any callbacks as appropriate
                // for the script type.

                var scripts = nodeComponent.scripts ? [].concat(nodeComponent.scripts) : []; // accept either an array or a single item

                var baseURI = self.uri(nodeID, true);

                async.map(scripts, function (script, map_callback_async /* ( err, result ) */) {

                    if (self.valueHasType(script)) {
                        if (script.source) {
                            self.loadScript(script.source, baseURI, function (scriptText) /* async */ { // TODO: this load would be better left to the driver, which may want to ignore it in certain cases, but that would require a completion callback from kernel.execute()
                                map_callback_async(undefined, {
                                    text: scriptText,
                                    type: script.type
                                });
                            }, function (errorMessage) {
                                map_callback_async(errorMessage, undefined);
                            });
                        } else {
                            map_callback_async(undefined, {
                                text: script.text,
                                type: script.type
                            });
                        }
                    } else {
                        map_callback_async(undefined, {
                            text: script,
                            type: undefined
                        });
                    }

                }, function (err, scripts) /* async */ {

                    // Suppress kernel reentry so that initialization functions don't make any
                    // changes during replication.

                    self.models.kernel.disable();

                    // Create each script.

                    scripts.forEach(function (script) {
                        self.execute(nodeID, script.text, script.type); // TODO: callback
                    });

                    // Restore kernel reentry.

                    self.models.kernel.enable();

                    series_callback_async(err, undefined);
                });

            },

        ], function (err, results) /* async */ {

            callback_async && callback_async(nodeID);

        });

        this.logger.debugu();

        return nodeComponent;
    }

    // -- getNode ------------------------------------------------------------------------------

    /// @name module:vwf.getNode
    /// 
    /// @see {@link module:vwf/api/kernel.getNode}

    getNode(nodeID, full, normalize, proto) { // TODO: options to include/exclude children, prototypes

        this.logger.debuggx("getNode", nodeID, full);

        var node = this.nodes.existing[nodeID];

        // Start the descriptor.

        var nodeComponent = {};

        // Arrange the component as a patch if the node originated in a URI component. We want
        // to refer to the original URI but apply any changes that have been made to the node
        // since it was loaded.

        var patches = this.models.object.patches(nodeID),
            patched = false;

        if (node.patchable) {
            nodeComponent.patches = node.uri || nodeID;
        } else {
            nodeComponent.id = nodeID;
        }

        // Intrinsic state. These don't change once created, so they can be omitted if we're
        // patching.

        if (full || !node.patchable) {

            var intrinsics = this.intrinsics(nodeID); // source, type

            var prototypeID = this.prototype(nodeID);

            if (prototypeID === undefined) {
                nodeComponent.extends = null;
            } else if (prototypeID !== this.kutility.protoNodeURI) {
                nodeComponent.extends = this.getNode(prototypeID); // TODO: move to vwf/model/object and get from intrinsics
            }

            nodeComponent.implements = this.behaviors(nodeID).map(function (behaviorID) {
                return this.getNode(behaviorID); // TODO: move to vwf/model/object and get from intrinsics
            }, this);

            nodeComponent.implements.length || delete nodeComponent.implements;

            if (intrinsics.source !== undefined) nodeComponent.source = intrinsics.source;
            if (intrinsics.type !== undefined) nodeComponent.type = intrinsics.type;

        }

        // Internal state.
        //patches = patches ? patches : {}
        if (full || !node.patchable || patches.internals) {

            var internals = this.models.object.internals(nodeID); // sequence and random

            nodeComponent.sequence = internals.sequence;
            nodeComponent.random = internals.random;

        }

        // Suppress kernel reentry so that we can read the state without coloring from any
        // scripts.

        this.models.kernel.disable();

        // Properties.

        if (full || !node.patchable) {

            // Want everything, or only want patches but the node is not patchable.

            nodeComponent.properties = this.getProperties(nodeID);

            // Description of Getters & Setters
            let jsProps = this.models.javascript.nodes[nodeID];
            let getters = jsProps.private.getters;
            let setters = jsProps.private.setters;

            Object.keys(nodeComponent.properties).forEach(el => {

                if (Object.keys(getters).includes(el) || Object.keys(setters).includes(el)) {

                    let prop = {
                        value: nodeComponent.properties[el]
                    }

                    if (typeof getters[el] == 'function') {
                        let fn = getters[el].toString()
                        prop.get = fn.slice(fn.indexOf("{") + 1, fn.lastIndexOf("}"));

                    } else {
                        prop.get = ""
                    }

                    if (typeof setters[el] == 'function') {
                        let fn = setters[el].toString()
                        prop.set = fn.slice(fn.indexOf("{") + 1, fn.lastIndexOf("}"));
                    } else {
                        prop.set = ""
                    }


                    if(prop.get == "" && prop.set == ""){
                        //let val = prop.value;
                        // delete prop.get;
                        // delete prop.set;
                        prop = prop.value;
                    }

                    nodeComponent.properties[el] = prop
                }
            })
            ///end of Getters & Setters

            for (var propertyName in nodeComponent.properties) {
                var propertyValue = nodeComponent.properties[propertyName];

                if (propertyValue === undefined) {
                    delete nodeComponent.properties[propertyName];
                } else if (this.kutility.valueIsNodeReference(propertyValue)) {
                    // Translate kernel node references into descriptor node references.
                    nodeComponent.properties[propertyName] = {
                        node: propertyValue.id
                    };
                }

            }

        } else if (node.properties.changes) {

            // The node is patchable and properties have changed.

            nodeComponent.properties = {};

            Object.keys(node.properties.changes).forEach(function (propertyName) {

                if (node.properties.changes[propertyName] !== "removed") { // TODO: handle delete

                    var propertyValue = this.getProperty(nodeID, propertyName);

                    if (this.kutility.valueIsNodeReference(propertyValue)) {
                        // Translate kernel node references into descriptor node references.
                        nodeComponent.properties[propertyName] = {
                            node: propertyValue.id
                        };
                    } else {
                        nodeComponent.properties[propertyName] = propertyValue;
                    }

                }

            }, this);

        }

        if (Object.keys(nodeComponent.properties).length == 0) {
            delete nodeComponent.properties;
        } else {
            patched = true;
        }

        // Methods.

        if (full || !node.patchable) {

            Object.keys(node.methods.existing).forEach(function (methodName) {
                nodeComponent.methods = nodeComponent.methods || {};
                nodeComponent.methods[methodName] = this.getMethod(nodeID, methodName);
                patched = true;
            }, this);

        } else if (node.methods.changes) {

            Object.keys(node.methods.changes).forEach(function (methodName) {
                if (node.methods.changes[methodName] !== "removed") { // TODO: handle delete
                    nodeComponent.methods = nodeComponent.methods || {};
                    nodeComponent.methods[methodName] = this.getMethod(nodeID, methodName);
                    patched = true;
                }
            }, this);

        }

        // Events.

        var events = full || !node.patchable ?
            node.events.existing : node.events.changes;

        if (events) {
            Object.keys(events).forEach(function (eventName) {
                nodeComponent.events = nodeComponent.events || {};
                nodeComponent.events[eventName] = this.getEvent(nodeID, eventName);
                patched = true;
            }, this);
        }

        // Restore kernel reentry.

        this.models.kernel.enable();

        // Children.

        nodeComponent.children = {};

        this.children(nodeID).forEach(function (childID) {
            nodeComponent.children[this.name(childID)] = this.getNode(childID, full);
        }, this);

        for (var childName in nodeComponent.children) { // TODO: distinguish add, change, remove
            if (nodeComponent.children[childName] === undefined) {
                delete nodeComponent.children[childName];
            }
        }

        ////CHECK FOR DELETED PROTO NODES

        nodeComponent.childrenDeleted = {};

        Object.keys(node.childsDeleted).forEach((childName) => {
            nodeComponent.childrenDeleted[childName] = null//node.childsDeleted[childName];
            patched = true;
        });

        ////

        if (Object.keys(nodeComponent.children).length == 0) {
            delete nodeComponent.children;
        } else {
            patched = true;
        }

        // Scripts.

        // TODO: scripts

        if (node.scripts) {
            console.log("SCRIPTS: ", node.scripts)
        }


        // Normalize for consistency.

        if (normalize) {
            nodeComponent = self.utility.transform(
                nodeComponent, self.utility.transforms.hash);
        }

        this.logger.debugu();

        // Return the descriptor created, unless it was arranged as a patch and there were no
        // changes. Otherwise, return the URI if this is the root of a URI component.

        if (full || !node.patchable || patched) {
            return nodeComponent;
        } else if (node.uri) {
            return node.uri;
        } else {
            return undefined;
        }

    };

    // -- hashNode -----------------------------------------------------------------------------

    /// @name module:vwf.hashNode
    /// 
    /// @see {@link module:vwf/api/kernel.hashNode}

    hashNode(nodeID) { // TODO: works with patches?  // TODO: only for nodes from getNode( , , true )

        this.logger.debuggx("hashNode", typeof nodeID == "object" ? nodeID.id : nodeID);

        var nodeComponent = typeof nodeID == "object" ? nodeID : this.getNode(nodeID, true, true);

        // Hash the intrinsic state.

        var internal = {
            id: nodeComponent.id,
            source: nodeComponent.source,
            type: nodeComponent.type
        }; // TODO: get subset same way as getNode() puts them in without calling out specific field names

        internal.source === undefined && delete internal.source;
        internal.type === undefined && delete internal.type;

        var hashi = "i" + Crypto.MD5(JSON.stringify(internal)).toString().substring(0, 16);

        // Hash the properties.

        var properties = nodeComponent.properties || {};

        var hashp = Object.keys(properties).length ?
            "p" + Crypto.MD5(JSON.stringify(properties)).toString().substring(0, 16) : undefined;

        // Hash the children.

        var children = nodeComponent.children || {};

        var hashc = Object.keys(children).length ?
            "c" + Crypto.MD5(JSON.stringify(children)).toString().substring(0, 16) : undefined;

        this.logger.debugu();

        // Generate the combined hash.

        return hashi + (hashp ? "." + hashp : "") + (hashc ? "/" + hashc : "");
    }


    // -- createChild --------------------------------------------------------------------------

    /// When we arrive here, we have a prototype node in hand (by way of its ID) and an object
    /// containing a component specification. We now need to create and assemble the new node.
    /// 
    /// The VWF manager doesn't directly manipulate any node. The various models act in
    /// federation to create the greater model. The manager simply routes messages within the
    /// system to allow the models to maintain the necessary data. Additionally, the views
    /// receive similar messages that allow them to keep their interfaces current.
    ///
    /// To create a node, we simply assign a new ID, then invoke a notification on each model and
    /// a notification on each view.
    /// 
    /// createChild may complete asynchronously due to its dependence on createNode and the
    /// creatingNode and createdNode driver calls. To prevent actions from executing out of
    /// order, queue processing must be suspended while createChild is in progress. createNode
    /// and the driver callbacks suspend the queue when necessary, but additional calls to
    /// suspend and resume the queue may be needed if other async operations are added.
    /// 
    /// @name module:vwf.createChild
    /// 
    /// @see {@link module:vwf/api/kernel.createChild}

    createChild(nodeID, childName, childComponent, childURI, callback_async /* ( childID ) */) {

        let self = this;

        this.logger.debuggx("createChild", function () {
            return [nodeID, childName, JSON.stringify(self.loggableComponent(childComponent)), childURI];
        });

        childComponent = self.normalizedComponent(childComponent);

        var child, childID, childIndex, childPrototypeID, childBehaviorIDs = [],
            deferredInitializations = {};

        var resolvedSource; // resolved `childComponent.source` for the drivers.

        // Determine if we're replicating previously-saved state, or creating a fresh object.

        var replicating = !!childComponent.id;

        // Allocate an ID for the node. IDs must be unique and consistent across all clients
        // sharing the same instance regardless of the component load order. Each node maintains
        // a sequence counter, and we allocate the ID based on the parent's sequence counter and
        // ID. Top-level nodes take the ID from their origin URI when available or from a hash
        // of the descriptor. An existing ID is used when synchronizing to state drawn from
        // another client or to a previously-saved state.

        if (childComponent.id) { // incoming replication: pre-calculated id
            childID = childComponent.id;
            childIndex = this.children(nodeID).length;
        } else if (nodeID === 0) { // global: component's URI or hash of its descriptor
            childID = childURI ||
                Crypto.MD5(JSON.stringify(childComponent)).toString(); // TODO: MD5 may be too slow here
            childIndex = childURI;
        } else { // descendant: parent id + next from parent's sequence
            childID = nodeID + ":" + this.sequence(nodeID) +
                (this.configuration["randomize-ids"] ? "-" + ("0" + Math.floor(this.random(nodeID) * 100)).slice(-2) : "") +
                (this.configuration["humanize-ids"] ? "-" + childName.replace(/[^0-9A-Za-z_-]+/g, "-") : "");
            childIndex = this.children(nodeID).length;
        }

        // Register the node.

        child = self.nodes.create(childID, childPrototypeID, childBehaviorIDs, childURI, childName, nodeID);

        // Register the node in vwf/model/object. Since the kernel delegates many node
        // information functions to vwf/model/object, this serves to register it with the
        // kernel. The node must be registered before any async operations occur to ensure that
        // the parent's child list is correct when following siblings calculate their index
        // numbers.

        this.models.object.creatingNode(nodeID, childID, childPrototypeID, childBehaviorIDs,
            childComponent.source, childComponent.type, childIndex, childName); // TODO: move node metadata back to the kernel and only use vwf/model/object just as a property store?

        // The base URI for relative references is the URI of this node or the closest ancestor.

        var baseURI = this.uri(childID, true);

        // Construct the node.

        async.series([

            function (series_callback_async /* ( err, results ) */) {

                // Rudimentary support for `{ includes: prototype }`, which absorbs a prototype
                // descriptor into the child descriptor before creating the child. See the notes
                // in `createNode` and the `mergeDescriptors` limitations.

                // This first task always completes asynchronously (even if it doesn't perform
                // an async operation) so that the stack doesn't grow from node to node while
                // createChild() recursively traverses a component. If this task is moved,
                // replace it with an async stub, or make the next task exclusively async.

                if (self.componentIsDescriptor(childComponent) && childComponent.includes && self.componentIsURI(childComponent.includes)) { // TODO: for "includes:", accept an already-loaded component (which componentIsURI exludes) since the descriptor will be loaded again

                    var prototypeURI = childComponent.includes //require( "vwf/utility" ).resolveURI( childComponent.includes, baseURI );

                    var sync = true; // will loadComponent() complete synchronously?

                    self.loadComponent(prototypeURI, undefined, function (prototypeDescriptor) /* async */ {

                        // Resolve relative references with respect to the included component.

                        prototypeDescriptor = self.resolvedDescriptor(prototypeDescriptor, prototypeURI);

                        // Merge the child descriptor onto the `includes` descriptor.

                        childComponent = self.mergeDescriptors(childComponent, prototypeDescriptor); // modifies prototypeDescriptor

                        if (sync) {

                            self.virtualTime.suspend("before beginning " + childID); // suspend the queue

                            async.nextTick(function () {
                                series_callback_async(undefined, undefined);
                                self.virtualTime.resume("after beginning " + childID); // resume the queue; may invoke dispatch(), so call last before returning to the host
                            });

                        } else {
                            series_callback_async(undefined, undefined);
                        }

                    }, function (errorMessage) {
                        childComponent = undefined;
                        series_callback_async(errorMessage, undefined);
                    });

                    sync = false; // not if we got here first

                } else {

                    self.virtualTime.suspend("before beginning " + childID); // suspend the queue

                    async.nextTick(function () {
                        series_callback_async(undefined, undefined);
                        self.virtualTime.resume("after beginning " + childID); // resume the queue; may invoke dispatch(), so call last before returning to the host
                    });

                }

            },

            function (series_callback_async /* ( err, results ) */) {

                // Create the prototype and behavior nodes (or locate previously created
                // instances).

                async.parallel([

                    function (parallel_callback_async /* ( err, results ) */) {

                        // Create or find the prototype and save the ID in childPrototypeID.

                        if (childComponent.extends !== null) { // TODO: any way to prevent node loading node as a prototype without having an explicit null prototype attribute in node?

                            var prototypeComponent = childComponent.extends || self.kutility.protoNodeURI;

                            self.createNode(prototypeComponent, undefined, baseURI, function (prototypeID) /* async */ {
                                childPrototypeID = prototypeID;

                                // TODO: the GLGE driver doesn't handle source/type or properties in prototypes properly; as a work-around pull those up into the component when not already defined
                                if (!childComponent.source) {
                                    var prototype_intrinsics = self.intrinsics(prototypeID);
                                    if (prototype_intrinsics.source) {
                                        var prototype_uri = self.uri(prototypeID);
                                        var prototype_properties = self.getProperties(prototypeID);
                                        childComponent.source = prototype_intrinsics.source //require( "vwf/utility" ).resolveURI( prototype_intrinsics.source, prototype_uri );
                                        childComponent.type = prototype_intrinsics.type;
                                        childComponent.properties = childComponent.properties || {};
                                        Object.keys(prototype_properties).forEach(function (prototype_property_name) {
                                            if (childComponent.properties[prototype_property_name] === undefined && prototype_property_name != "transform") {
                                                childComponent.properties[prototype_property_name] = prototype_properties[prototype_property_name];
                                            }
                                        });
                                    }
                                }
                                parallel_callback_async(undefined, undefined);
                            });
                        } else {
                            childPrototypeID = undefined;
                            parallel_callback_async(undefined, undefined);
                        }

                    },

                    function (parallel_callback_async /* ( err, results ) */) {

                        // Create or find the behaviors and save the IDs in childBehaviorIDs.

                        var behaviorComponents = childComponent.implements ? [].concat(childComponent.implements) : []; // accept either an array or a single item

                        async.map(behaviorComponents, function (behaviorComponent, map_callback_async /* ( err, result ) */) {
                            self.createNode(behaviorComponent, undefined, baseURI, function (behaviorID) /* async */ {
                                map_callback_async(undefined, behaviorID);
                            });
                        }, function (err, behaviorIDs) /* async */ {
                            childBehaviorIDs = behaviorIDs;
                            parallel_callback_async(err, undefined);
                        });

                    },

                ], function (err, results) /* async */ {
                    series_callback_async(err, undefined);
                });

            },

            function (series_callback_async /* ( err, results ) */) {

                // Re-register the node now that we have the prototypes and behaviors.

                child = self.nodes.create(childID, childPrototypeID, childBehaviorIDs, childURI, childName, nodeID);

                // For the proto-prototype node `node.vwf`, register the meta events.

                if (childID === self.kutility.protoNodeURI) {
                    child.events.create(self.namespaceEncodedName(["properties", "created"]));
                    child.events.create(self.namespaceEncodedName(["properties", "initialized"]));
                    child.events.create(self.namespaceEncodedName(["properties", "deleted"]));
                    child.events.create(self.namespaceEncodedName(["methods", "created"]));
                    child.events.create(self.namespaceEncodedName(["methods", "deleted"]));
                    child.events.create(self.namespaceEncodedName(["events", "created"]));
                    child.events.create(self.namespaceEncodedName(["events", "deleted"]));
                    child.events.create(self.namespaceEncodedName(["children", "added"]));
                    child.events.create(self.namespaceEncodedName(["children", "removed"]));
                }

                // Re-register the node in vwf/model/object now that we have the prototypes and
                // behaviors. vwf/model/object knows that we call it more than once and only
                // updates the new information.

                self.models.object.creatingNode(nodeID, childID, childPrototypeID, childBehaviorIDs,
                    childComponent.source, childComponent.type, childIndex, childName); // TODO: move node metadata back to the kernel and only use vwf/model/object just as a property store?

                // Resolve the asset source URL for the drivers.

                resolvedSource = childComponent.source && childComponent.source
                //require( "vwf/utility" ).resolveURI( childComponent.source, baseURI );

                // Call creatingNode() on each model. The node is considered to be constructed
                // after all models have run.

                async.forEachSeries(self.models, function (model, each_callback_async /* ( err ) */) {

                    var driver_ready = true;
                    var timeoutID;

                    // TODO: suppress kernel reentry here (just for childID?) with kernel/model showing a warning when breached; no actions are allowed until all drivers have seen creatingNode()

                    model.creatingNode && model.creatingNode(nodeID, childID, childPrototypeID, childBehaviorIDs,
                        resolvedSource, childComponent.type, childIndex, childName,
                        function (ready) /* async */ {

                            if (driver_ready && !ready) {
                                suspend();
                            } else if (!driver_ready && ready) {
                                resume();
                            }

                            function suspend() {
                                self.virtualTime.suspend("while loading " + childComponent.source + " for " + childID + " in creatingNode"); // suspend the queue
                                timeoutID = window.setTimeout(function () {
                                    resume("timeout loading " + childComponent.source)
                                }, self.configuration["load-timeout"] * 1000);
                                driver_ready = false;
                            }

                            function resume(err) {
                                window.clearTimeout(timeoutID);
                                driver_ready = true;
                                err && self.logger.warnx("createChild", nodeID, childName + ":", err);
                                each_callback_async(err); // resume createChild()
                                self.virtualTime.resume("after loading " + childComponent.source + " for " + childID + " in creatingNode"); // resume the queue; may invoke dispatch(), so call last before returning to the host
                            }

                        });

                    // TODO: restore kernel reentry here

                    driver_ready && each_callback_async(undefined);

                }, function (err) /* async */ {
                    series_callback_async(err, undefined);
                });

            },

            function (series_callback_async /* ( err, results ) */) {

                // Call createdNode() on each view. The view is being notified of a node that has
                // been constructed.

                async.forEach(self.views, function (view, each_callback_async /* ( err ) */) {

                    var driver_ready = true;
                    var timeoutID;

                    view.createdNode && view.createdNode(nodeID, childID, childPrototypeID, childBehaviorIDs,
                        resolvedSource, childComponent.type, childIndex, childName,
                        function (ready) /* async */ {

                            if (driver_ready && !ready) {
                                suspend();
                            } else if (!driver_ready && ready) {
                                resume();
                            }

                            function suspend() {
                                self.virtualTime.suspend("while loading " + childComponent.source + " for " + childID + " in createdNode"); // suspend the queue
                                timeoutID = window.setTimeout(function () {
                                    resume("timeout loading " + childComponent.source)
                                }, self.configuration["load-timeout"] * 1000);
                                driver_ready = false;
                            }

                            function resume(err) {
                                window.clearTimeout(timeoutID);
                                driver_ready = true;
                                err && self.logger.warnx("createChild", nodeID, childName + ":", err);
                                each_callback_async(err); // resume createChild()
                                self.virtualTime.resume("after loading " + childComponent.source + " for " + childID + " in createdNode"); // resume the queue; may invoke dispatch(), so call last before returning to the host
                            }

                        });

                    driver_ready && each_callback_async(undefined);

                }, function (err) /* async */ {
                    series_callback_async(err, undefined);
                });

            },

            function (series_callback_async /* ( err, results ) */) {

                // Set the internal state.

                self.models.object.internals(childID, childComponent);

                // Suppress kernel reentry so that we can read the state without coloring from
                // any scripts.

                replicating && self.models.kernel.disable();

                // Create the properties, methods, and events. For each item in each set, invoke
                // createProperty(), createMethod(), or createEvent() to create the field. Each
                // delegates to the models and views as above.

                childComponent.properties && Object.keys(childComponent.properties).forEach(function (propertyName) {
                    var propertyValue = childComponent.properties[propertyName];

                    var value = propertyValue,
                        get, set, create;

                    if (self.valueHasAccessors(propertyValue)) {
                        value = propertyValue.node ? self.kutility.nodeReference(propertyValue.node) : propertyValue.value;
                        get = propertyValue.get;
                        set = propertyValue.set;
                        create = propertyValue.create;
                    }

                    // Is the property specification directing us to create a new property, or
                    // initialize a property already defined on a prototype?

                    // Create a new property if an explicit getter or setter are provided or if
                    // the property is not defined on a prototype. Initialize the property when
                    // the property is already defined on a prototype and no explicit getter or
                    // setter are provided.

                    var creating = create || // explicit create directive, or
                        get !== undefined || set !== undefined || // explicit accessor, or
                        !child.properties.has(propertyName); // not defined on prototype

                    // Are we assigning the value here, or deferring assignment until the node
                    // is constructed because setters will run?

                    var assigning = value === undefined || // no value, or
                        set === undefined && (creating || !self.nodePropertyHasSetter.call(self, childID, propertyName)) || // no setter, or
                        replicating; // replicating previously-saved state (setters never run during replication)

                    if (!assigning) {
                        deferredInitializations[propertyName] = value;
                        value = undefined;
                    }

                    // Create or initialize the property.

                    if (creating) {
                        self.createProperty(childID, propertyName, value, get, set);
                    } else {
                        self.setProperty(childID, propertyName, value);
                    }

                });

                childComponent.methods && Object.keys(childComponent.methods).forEach(function (methodName) {
                    var methodValue = childComponent.methods[methodName];

                    if (self.valueHasBody(methodValue)) {
                        self.createMethod(childID, methodName, methodValue.parameters, methodValue.body);
                    } else {
                        self.createMethod(childID, methodName, undefined, methodValue);
                    }

                });

                childComponent.events && Object.keys(childComponent.events).forEach(function (eventName) {
                    var eventValue = childComponent.events[eventName];

                    if (self.valueHasBody(eventValue)) {
                        self.createEvent(childID, eventName, eventValue.parameters);
                        self.setEvent(childID, eventName, eventValue); // set the listeners since `createEvent` can't do it yet
                    } else {
                        self.createEvent(childID, eventName, undefined);
                    }

                });

                // Restore kernel reentry.

                replicating && self.models.kernel.enable();

                // Create and attach the children. For each child, call createChild() with the
                // child's component specification. createChild() delegates to the models and
                // views as before.

                async.forEach(Object.keys(childComponent.children || {}), function (childName, each_callback_async /* ( err ) */) {
                    var childValue = childComponent.children[childName];

                    self.createChild(childID, childName, childValue, undefined, function (childID) /* async */ { // TODO: add in original order from childComponent.children  // TODO: propagate childURI + fragment identifier to children of a URI component?
                        each_callback_async(undefined);
                    });

                }, function (err) /* async */ {
                    series_callback_async(err, undefined);
                });

            },

            function (series_callback_async /* ( err, results ) */) {

                // Attach the scripts. For each script, load the network resource if the script is
                // specified as a URI, then once loaded, call execute() to direct any model that
                // manages scripts of this script's type to evaluate the script where it will
                // perform any immediate actions and retain any callbacks as appropriate for the
                // script type.

                var scripts = childComponent.scripts ? [].concat(childComponent.scripts) : []; // accept either an array or a single item

                async.map(scripts, function (script, map_callback_async /* ( err, result ) */) {

                    if (self.valueHasType(script)) {
                        if (script.source) {
                            self.loadScript(script.source, baseURI, function (scriptText) /* async */ { // TODO: this load would be better left to the driver, which may want to ignore it in certain cases, but that would require a completion callback from kernel.execute()
                                map_callback_async(undefined, {
                                    text: scriptText,
                                    type: script.type
                                });
                            }, function (errorMessage) {
                                map_callback_async(errorMessage, undefined);
                            });
                        } else {
                            map_callback_async(undefined, {
                                text: script.text,
                                type: script.type
                            });
                        }
                    } else {
                        map_callback_async(undefined, {
                            text: script,
                            type: undefined
                        });
                    }

                }, function (err, scripts) /* async */ {

                    // Watch for any async kernel calls generated as we run the scripts and wait
                    // for them complete before completing the node.

                    self.models.kernel.capturingAsyncs(function () {

                        // Suppress kernel reentry so that initialization functions don't make
                        // any changes during replication.

                        replicating && self.models.kernel.disable();

                        // Create each script.

                        scripts.forEach(function (script) {
                            self.execute(childID, script.text, script.type); // TODO: callback
                        });

                        // Perform initializations for properties with setter functions. These
                        // are assigned here so that the setters run on a fully-constructed node.

                        Object.keys(deferredInitializations).forEach(function (propertyName) {
                            self.setProperty(childID, propertyName, deferredInitializations[propertyName]);
                        });

                        // TODO: Adding the node to the tickable list here if it contains a tick() function in JavaScript at initialization time. Replace with better control of ticks on/off and the interval by the node.

                        if (self.execute(childID, "Boolean( this.tick )")) {
                            self.tickable.nodeIDs.push(childID);
                        }

                        // Restore kernel reentry.
                        replicating && self.models.kernel.enable();

                    }, function () {

                        // This function is called when all asynchronous calls from the previous
                        // function have returned.

                        // Call initializingNode() on each model and initializedNode() on each
                        // view to indicate that the node is fully constructed.

                        // Since nodes don't (currently) inherit their prototypes' children,
                        // for each prototype also call initializingNodeFromPrototype() to allow
                        // model drivers to apply the prototypes' initializers to the node.

                        async.forEachSeries(self.prototypes(childID, true).reverse().concat(childID),
                            function (childInitializingNodeID, each_callback_async /* err */) {

                                // Call initializingNode() on each model.

                                self.models.kernel.capturingAsyncs(function () {

                                    self.models.forEach(function (model) {

                                        // Suppress kernel reentry so that initialization functions
                                        // don't make any changes during replication.
                                        replicating && self.models.kernel.disable();

                                        // For a prototype, call `initializingNodeFromPrototype` to
                                        // run the prototype's initializer on the node. For the
                                        // node, call `initializingNode` to run its own initializer.
                                        // 
                                        // `initializingNodeFromPrototype` is separate from
                                        // `initializingNode` so that `initializingNode` remains a
                                        // single call that indicates that the node is fully
                                        // constructed. Existing drivers, and any drivers that don't
                                        // care about prototype initializers will by default ignore
                                        // the intermediate initializations.
                                        // (`initializingNodeFromPrototype` was added in 0.6.23.)

                                        if (childInitializingNodeID !== childID) {
                                            model.initializingNodeFromPrototype &&
                                                model.initializingNodeFromPrototype(nodeID, childID, childInitializingNodeID);
                                        } else {
                                            model.initializingNode &&
                                                model.initializingNode(nodeID, childID, childPrototypeID, childBehaviorIDs,
                                                    resolvedSource, childComponent.type, childIndex, childName);
                                        }

                                        // Restore kernel reentry.
                                        replicating && self.models.kernel.enable();

                                    });

                                }, function () {
                                    each_callback_async(undefined);
                                });

                            },
                            function (err) /* async */ {

                                // Call initializedNode() on each view.

                                self.views.forEach(function (view) {
                                    view.initializedNode && view.initializedNode(nodeID, childID, childPrototypeID, childBehaviorIDs,
                                        resolvedSource, childComponent.type, childIndex, childName);
                                });

                                // Mark the node as initialized.

                                self.nodes.initialize(childID);

                                // Send the meta event into the application.

                                if (!replicating && nodeID !== 0) {
                                    self.fireEvent(nodeID, ["children", "added"],
                                        [childIndex, self.kutility.nodeReference(childID)]);
                                }

                                // Dismiss the loading spinner
                                if (childID === self.application()) {
                                    _app.hideProgressBar();
                                }

                                series_callback_async(err, undefined);
                            });
                    });
                });
            },

        ], function (err, results) /* async */ {

            // The node is complete. Invoke the callback method and pass the new node ID and the
            // ID of its prototype. If this was the root node for the application, the
            // application is now fully initialized.

            // Always complete asynchronously so that the stack doesn't grow from node to node
            // while createChild() recursively traverses a component.

            if (callback_async) {

                self.virtualTime.suspend("before completing " + childID); // suspend the queue

                async.nextTick(function () {
                    callback_async(childID);
                    self.virtualTime.resume("after completing " + childID); // resume the queue; may invoke dispatch(), so call last before returning to the host
                });

            }

        });

        this.logger.debugu();
    }

    // -- deleteChild --------------------------------------------------------------------------

    /// @name module:vwf.deleteChild
    /// 
    /// @see {@link module:vwf/api/kernel.deleteChild}

    deleteChild(nodeID, childName, replaceFlag) {

        var childID = this.children(nodeID).filter(function (childID) {
            return this.name(childID) === childName;
        }, this)[0];

        if (childID !== undefined) {
            return this.deleteNode(childID, replaceFlag);
        }

    }

    // -- addChild -----------------------------------------------------------------------------

    /// @name module:vwf.addChild
    /// 
    /// @see {@link module:vwf/api/kernel.addChild}

    addChild(nodeID, childID, childName) {

        this.logger.debuggx("addChild", nodeID, childID, childName);

        // Call addingChild() on each model. The child is considered added after all models have
        // run.

        this.models.forEach(function (model) {
            model.addingChild && model.addingChild(nodeID, childID, childName);
        });

        // Call addedChild() on each view. The view is being notified that a child has been
        // added.

        this.views.forEach(function (view) {
            view.addedChild && view.addedChild(nodeID, childID, childName);
        });

        this.logger.debugu();
    }

    // -- removeChild --------------------------------------------------------------------------

    /// @name module:vwf.removeChild
    /// 
    /// @see {@link module:vwf/api/kernel.removeChild}

    removeChild(nodeID, childID) {

        this.logger.debuggx("removeChild", nodeID, childID);

        // Call removingChild() on each model. The child is considered removed after all models
        // have run.

        this.models.forEach(function (model) {
            model.removingChild && model.removingChild(nodeID, childID);
        });

        // Call removedChild() on each view. The view is being notified that a child has been
        // removed.

        this.views.forEach(function (view) {
            view.removedChild && view.removedChild(nodeID, childID);
        });

        this.logger.debugu();
    }

    // -- setProperties ------------------------------------------------------------------------

    /// Set all of the properties for a node.
    /// 
    /// @name module:vwf.setProperties
    /// 
    /// @see {@link module:vwf/api/kernel.setProperties}

    setProperties(nodeID, properties) { // TODO: rework as a cover for setProperty(), or remove; passing all properties to each driver is impractical since initializing and setting are different, and reentry can't be controlled when multiple sets are in progress.

        let self = this;
        this.logger.debuggx("setProperties", nodeID, properties);

        var node = self.nodes.existing[nodeID];

        var entrants = this.setProperty.entrants;

        // Call settingProperties() on each model.

        properties = this.models.reduceRight(function (intermediate_properties, model, index) { // TODO: note that we can't go left to right and stop after the first that accepts the set since we are setting all of the properties as a batch; verify that this creates the same result as calling setProperty individually on each property and that there are no side effects from setting through a driver after the one that handles the set.

            var model_properties = {};

            if (model.settingProperties) {

                model_properties = model.settingProperties(nodeID, properties);

            } else if (model.settingProperty) {

                Object.keys(node.properties.existing).forEach(function (propertyName) {

                    if (properties[propertyName] !== undefined) {

                        var reentry = entrants[nodeID + '-' + propertyName] = {
                            index: index
                        }; // the active model number from this call  // TODO: need unique nodeID+propertyName hash

                        model_properties[propertyName] =
                            model.settingProperty(nodeID, propertyName, properties[propertyName]);
                        if (self.models.kernel.blocked()) {
                            model_properties[propertyName] = undefined; // ignore result from a blocked setter
                        }

                        delete entrants[nodeID + '-' + propertyName];

                    }

                });

            }

            Object.keys(node.properties.existing).forEach(function (propertyName) {
                if (model_properties[propertyName] !== undefined) { // copy values from this model
                    intermediate_properties[propertyName] = model_properties[propertyName];
                } else if (intermediate_properties[propertyName] === undefined) { // as well as recording any new keys
                    intermediate_properties[propertyName] = undefined;
                }
            });

            return intermediate_properties;

        }, {});

        // Record the change.

        if (node.initialized && node.patchable) {
            Object.keys(properties).forEach(function (propertyName) {
                node.properties.change(propertyName);
            });
        }

        // Call satProperties() on each view.

        this.views.forEach(function (view) {

            if (view.satProperties) {
                view.satProperties(nodeID, properties);
            } else if (view.satProperty) {
                for (var propertyName in properties) {
                    view.satProperty(nodeID, propertyName, properties[propertyName]); // TODO: be sure this is the value actually set, not the incoming value
                }
            }

        });

        this.logger.debugu();

        return properties;
    }

    // -- getProperties ------------------------------------------------------------------------

    /// Get all of the properties for a node.
    /// 
    /// @name module:vwf.getProperties
    /// 
    /// @see {@link module:vwf/api/kernel.getProperties}

    getProperties(nodeID) { // TODO: rework as a cover for getProperty(), or remove; passing all properties to each driver is impractical since reentry can't be controlled when multiple gets are in progress.

        let self = this;
        this.logger.debuggx("getProperties", nodeID);

        var node = self.nodes.existing[nodeID];

        var entrants = this.getProperty.entrants;

        // Call gettingProperties() on each model.

        var properties = this.models.reduceRight(function (intermediate_properties, model, index) { // TODO: note that we can't go left to right and take the first result since we are getting all of the properties as a batch; verify that this creates the same result as calling getProperty individually on each property and that there are no side effects from getting through a driver after the one that handles the get.

            var model_properties = {};

            if (model.gettingProperties) {

                model_properties = model.gettingProperties(nodeID, properties);

            } else if (model.gettingProperty) {

                Object.keys(node.properties.existing).forEach(function (propertyName) {

                    var reentry = entrants[nodeID + '-' + propertyName] = {
                        index: index
                    }; // the active model number from this call  // TODO: need unique nodeID+propertyName hash

                    model_properties[propertyName] =
                        model.gettingProperty(nodeID, propertyName, intermediate_properties[propertyName]);
                    if (self.models.kernel.blocked()) {
                        model_properties[propertyName] = undefined; // ignore result from a blocked getter
                    }

                    delete entrants[nodeID + '-' + propertyName];

                });

            }

            Object.keys(node.properties.existing).forEach(function (propertyName) {
                if (model_properties[propertyName] !== undefined) { // copy values from this model
                    intermediate_properties[propertyName] = model_properties[propertyName];
                } else if (intermediate_properties[propertyName] === undefined) { // as well as recording any new keys
                    intermediate_properties[propertyName] = undefined;
                }
            });

            return intermediate_properties;

        }, {});

        // Call gotProperties() on each view.

        this.views.forEach(function (view) {

            if (view.gotProperties) {
                view.gotProperties(nodeID, properties);
            } else if (view.gotProperty) {
                for (var propertyName in properties) {
                    view.gotProperty(nodeID, propertyName, properties[propertyName]); // TODO: be sure this is the value actually gotten and not an intermediate value from above
                }
            }

        });

        this.logger.debugu();

        return properties;
    }

    // -- createProperty -----------------------------------------------------------------------

    /// Create a property on a node and assign an initial value.
    /// 
    /// @name module:vwf.createProperty
    /// 
    /// @see {@link module:vwf/api/kernel.createProperty}

    createProperty(nodeID, propertyName, propertyValue, propertyGet, propertySet) {
        let self = this;
        this.logger.debuggx("createProperty", function () {
            return [nodeID, propertyName, JSON.stringify(self.loggableValue(propertyValue)),
                self.loggableScript(propertyGet), self.loggableScript(propertySet)
            ];
        });

        var node = self.nodes.existing[nodeID];

        // Register the property.

        node.properties.create(propertyName, node.initialized && node.patchable);

        // Call creatingProperty() on each model. The property is considered created after all
        // models have run.

        this.models.forEach(function (model) {
            model.creatingProperty && model.creatingProperty(nodeID, propertyName, propertyValue,
                propertyGet, propertySet);
        });

        // Call createdProperty() on each view. The view is being notified that a property has
        // been created.

        this.views.forEach(function (view) {
            view.createdProperty && view.createdProperty(nodeID, propertyName, propertyValue,
                propertyGet, propertySet);
        });

        // Send the meta event into the application.

        if (this.models.kernel.enabled()) {
            this.fireEvent(nodeID, ["properties", "created"], [propertyName]);
        }

        this.logger.debugu();

        return propertyValue;
    }

    // -- setProperty --------------------------------------------------------------------------

    /// Set a property value on a node.
    /// 
    /// @name module:vwf.setProperty
    /// 
    /// @see {@link module:vwf/api/kernel.setProperty}

    setProperty(nodeID, propertyName, propertyValue) {
        let self = this;
        this.logger.debuggx("setProperty", function () {
            return [nodeID, propertyName, JSON.stringify(self.loggableValue(propertyValue))];
        });

        var node = self.nodes.existing[nodeID];

        // Record calls into this function by nodeID and propertyName so that models may call
        // back here (directly or indirectly) to delegate responses further down the chain
        // without causing infinite recursion.

        var entrants = this.setProperty.entrants;

        var entry = entrants[nodeID + '-' + propertyName] || {}; // the most recent call, if any  // TODO: need unique nodeID+propertyName hash
        var reentry = entrants[nodeID + '-' + propertyName] = {}; // this call

        // Select the actual driver calls. Create the property if it doesn't exist on this node
        // or its prototypes. Initialize it if it exists on a prototype but not on this node.
        // Set it if it already exists on this node.

        if (!node.properties.has(propertyName) || entry.creating) {
            reentry.creating = true;
            var settingPropertyEtc = "creatingProperty";
            var satPropertyEtc = "createdProperty";
            node.properties.create(propertyName, node.initialized && node.patchable);
        } else if (!node.properties.hasOwn(propertyName) || entry.initializing) {
            reentry.initializing = true;
            var settingPropertyEtc = "initializingProperty";
            var satPropertyEtc = "initializedProperty";
            node.properties.create(propertyName, node.initialized && node.patchable);
        } else {
            var settingPropertyEtc = "settingProperty";
            var satPropertyEtc = "satProperty";
        }

        // Keep track of the number of assignments made by this `setProperty` call and others
        // invoked indirectly by it, starting with the outermost call.

        var outermost = entrants.assignments === undefined;

        if (outermost) {
            entrants.assignments = 0;
        }

        // Have we been called for the same property on the same node for a property still being
        // assigned (such as when a setter function assigns the property to itself)? If so, then
        // the inner call should skip drivers that the outer call has already invoked, and the
        // outer call should complete without invoking drivers that the inner call will have
        // already called.

        var reentered = (entry.index !== undefined);

        // We'll need to know if the set was delegated to other properties or actually assigned
        // here.

        var delegated = false,
            assigned = false;

        // Call settingProperty() on each model. The first model to return a non-undefined value
        // has performed the set and dictates the return value. The property is considered set
        // after all models have run.

        this.models.some(function (model, index) {

            // Skip initial models that an outer call has already invoked for this node and
            // property (if any). If an inner call completed for this node and property, skip
            // the remaining models.

            if ((!reentered || index > entry.index) && !reentry.completed) {

                // Record the active model number.

                reentry.index = index;

                // Record the number of assignments made since the outermost call. When
                // `entrants.assignments` increases, a driver has called `setProperty` to make
                // an assignment elsewhere.

                var assignments = entrants.assignments;

                // Make the call.

                if (!delegated && !assigned) {
                    var value = model[settingPropertyEtc] && model[settingPropertyEtc](nodeID, propertyName, propertyValue);
                } else {
                    model[settingPropertyEtc] && model[settingPropertyEtc](nodeID, propertyName, undefined);
                }

                // Ignore the result if reentry is disabled and the driver attempted to call
                // back into the kernel. Kernel reentry is disabled during replication to 
                // prevent coloring from accessor scripts.

                if (this.models.kernel.blocked()) { // TODO: this might be better handled wholly in vwf/kernel/model by converting to a stage and clearing blocked results on the return
                    value = undefined;
                }

                // The property was delegated if the call made any assignments.

                if (entrants.assignments !== assignments) {
                    delegated = true;
                }

                // Otherwise if the call returned a value, the property was assigned here.
                else if (value !== undefined) {
                    entrants.assignments++;
                    assigned = true;
                }

                // Record the value actually assigned. This may differ from the incoming value
                // if it was range limited, quantized, etc. by the model. This is the value
                // passed to the views.

                if (value !== undefined) {
                    propertyValue = value;
                }

                // If we are setting, exit from the this.models.some() iterator once the value
                // has been set. Don't exit early if we are creating or initializing since every
                // model needs the opportunity to register the property.

                return settingPropertyEtc == "settingProperty" && (delegated || assigned);
            }

        }, this);

        // Record the change if the property was assigned here.

        if (assigned && node.initialized && node.patchable) {
            node.properties.change(propertyName);
        }

        // Call satProperty() on each view. The view is being notified that a property has
        // been set. Only call for value properties as they are actually assigned. Don't call
        // for accessor properties that have delegated to other properties. Notifying when
        // setting an accessor property would be useful, but since that information is
        // ephemeral, and views on late-joining clients would never see it, it's best to never
        // send those notifications.

        if (assigned) {
            this.views.forEach(function (view) {
                view[satPropertyEtc] && view[satPropertyEtc](nodeID, propertyName, propertyValue);
            });
        }

        if (reentered) {

            // For a reentrant call, restore the previous state and move the index forward to
            // cover the models we called.

            entrants[nodeID + '-' + propertyName] = entry;
            entry.completed = true;

        } else {

            // Delete the call record if this is the first, non-reentrant call here (the normal
            // case).

            delete entrants[nodeID + '-' + propertyName];

            // If the property was created or initialized, send the corresponding meta event
            // into the application.

            if (this.models.kernel.enabled()) {
                if (settingPropertyEtc === "creatingProperty") {
                    this.fireEvent(nodeID, ["properties", "created"], [propertyName]);
                } else if (settingPropertyEtc === "initializingProperty") {
                    this.fireEvent(nodeID, ["properties", "initialized"], [propertyName]);
                }
            }

        }

        // Clear the assignment counter when the outermost `setProperty` completes.

        if (outermost) {
            delete entrants.assignments;
        }

        this.logger.debugu();

        return propertyValue;
    }




    // -- getProperty --------------------------------------------------------------------------

    /// Get a property value for a node.
    /// 
    /// @name module:vwf.getProperty
    /// 
    /// @see {@link module:vwf/api/kernel.getProperty}

    getProperty(nodeID, propertyName, ignorePrototype) {

        this.logger.debuggx("getProperty", nodeID, propertyName);

        var propertyValue = undefined;

        // Record calls into this function by nodeID and propertyName so that models may call
        // back here (directly or indirectly) to delegate responses further down the chain
        // without causing infinite recursion.

        var entrants = this.getProperty.entrants;

        var entry = entrants[nodeID + '-' + propertyName] || {}; // the most recent call, if any  // TODO: need unique nodeID+propertyName hash
        var reentry = entrants[nodeID + '-' + propertyName] = {}; // this call

        // Keep track of the number of retrievals made by this `getProperty` call and others
        // invoked indirectly by it, starting with the outermost call.

        var outermost = entrants.retrievals === undefined;

        if (outermost) {
            entrants.retrievals = 0;
        }

        // Have we been called for the same property on the same node for a property still being
        // retrieved (such as when a getter function retrieves the property from itself)? If so,
        // then the inner call should skip drivers that the outer call has already invoked, and
        // the outer call should complete without invoking drivers that the inner call will have
        // already called.

        var reentered = (entry.index !== undefined);

        // We'll need to know if the get was delegated to other properties or actually retrieved
        // here.

        var delegated = false,
            retrieved = false;

        // Call gettingProperty() on each model. The first model to return a non-undefined value
        // dictates the return value.

        this.models.some(function (model, index) {

            // Skip initial models that an outer call has already invoked for this node and
            // property (if any). If an inner call completed for this node and property, skip
            // the remaining models.

            if ((!reentered || index > entry.index) && !reentry.completed) {

                // Record the active model number.

                reentry.index = index;

                // Record the number of retrievals made since the outermost call. When
                // `entrants.retrievals` increases, a driver has called `getProperty` to make
                // a retrieval elsewhere.

                var retrievals = entrants.retrievals;

                // Make the call.

                var value = model.gettingProperty &&
                    model.gettingProperty(nodeID, propertyName, propertyValue); // TODO: probably don't need propertyValue here

                // Ignore the result if reentry is disabled and the driver attempted to call
                // back into the kernel. Kernel reentry is disabled during replication to 
                // prevent coloring from accessor scripts.

                if (this.models.kernel.blocked()) { // TODO: this might be better handled wholly in vwf/kernel/model by converting to a stage and clearing blocked results on the return
                    value = undefined;
                }

                // The property was delegated if the call made any retrievals.

                if (entrants.retrievals !== retrievals) {
                    delegated = true;
                }

                // Otherwise if the call returned a value, the property was retrieved here.
                else if (value !== undefined) {
                    entrants.retrievals++;
                    retrieved = true;
                }

                // Record the value retrieved.

                if (value !== undefined) {
                    propertyValue = value;
                }

                // Exit from the this.models.some() iterator once we have a return value.

                return delegated || retrieved;
            }

        }, this);

        if (reentered) {

            // For a reentrant call, restore the previous state, move the index forward to cover
            // the models we called.

            entrants[nodeID + '-' + propertyName] = entry;
            entry.completed = true;

        } else {

            // Delete the call record if this is the first, non-reentrant call here (the normal
            // case).

            delete entrants[nodeID + '-' + propertyName];

            // Delegate to the behaviors and prototype if we didn't get a result from the
            // current node.

            if (propertyValue === undefined && !ignorePrototype) {

                if (this.behaviors(nodeID)) {

                    this.behaviors(nodeID).reverse().concat(this.prototype(nodeID)).
                        some(function (prototypeID, prototypeIndex, prototypeArray) {

                            if (prototypeIndex < prototypeArray.length - 1) {
                                propertyValue = this.getProperty(prototypeID, propertyName, true); // behavior node only, not its prototypes
                            } else if (prototypeID !== this.kutility.protoNodeURI) {
                                propertyValue = this.getProperty(prototypeID, propertyName); // prototype node, recursively
                            }

                            return propertyValue !== undefined;

                        }, this);

                }
            }

            // Call gotProperty() on each view.

            this.views.forEach(function (view) {
                view.gotProperty && view.gotProperty(nodeID, propertyName, propertyValue); // TODO: be sure this is the value actually gotten and not an intermediate value from above
            });

        }

        // Clear the retrieval counter when the outermost `getProperty` completes.

        if (outermost) {
            delete entrants.retrievals;
        }

        this.logger.debugu();

        return propertyValue;
    }



    // -- createMethod -------------------------------------------------------------------------

    /// @name module:vwf.createMethod
    /// 
    /// @see {@link module:vwf/api/kernel.createMethod}

    createMethod(nodeID, methodName, methodParameters, methodBody) {
        let self = this;
        this.logger.debuggx("createMethod", function () {
            return [nodeID, methodName, methodParameters, self.loggableScript(methodBody)];
        });

        var node = self.nodes.existing[nodeID];

        // Register the method.

        node.methods.create(methodName, node.initialized && node.patchable);

        // Call `creatingMethod` on each model. The method is considered created after all
        // models have run.

        this.models.forEach(function (model) {
            model.creatingMethod && model.creatingMethod(nodeID, methodName, methodParameters,
                methodBody);
        });

        // Call `createdMethod` on each view. The view is being notified that a method has been
        // created.

        this.views.forEach(function (view) {
            view.createdMethod && view.createdMethod(nodeID, methodName, methodParameters,
                methodBody);
        });

        // Send the meta event into the application.

        if (this.models.kernel.enabled()) {
            this.fireEvent(nodeID, ["methods", "created"], [methodName]);
        }

        this.logger.debugu();
    }

    // -- setMethod ----------------------------------------------------------------------------

    /// @name module:vwf.setMethod
    /// 
    /// @see {@link module:vwf/api/kernel.setMethod}

    setMethod(nodeID, methodName, methodHandler) {

        let self = this;

        this.logger.debuggx("setMethod", function () {
            return [nodeID, methodName]; // TODO loggable methodHandler
        });

        var node = this.nodes.existing[nodeID];

        methodHandler = this.normalizedHandler(methodHandler);

        if (!node.methods.hasOwn(methodName)) {

            // If the method doesn't exist on this node, delegate to `kernel.createMethod` to
            // create and assign the method.

            this.createMethod(nodeID, methodName, methodHandler.parameters, methodHandler.body); // TODO: result

        } else {

            // Call `settingMethod` on each model. The first model to return a non-undefined
            // value dictates the return value.

            this.models.some(function (model) {

                // Call the driver.

                var handler = model.settingMethod && model.settingMethod(nodeID, methodName, methodHandler);

                // Update the value to the value assigned if the driver handled it.

                if (handler !== undefined) {
                    methodHandler = self.utility.merge({}, handler); // omit `undefined` values
                }

                // Exit the iterator once a driver has handled the assignment.

                return handler !== undefined;

            });

            // Record the change.

            if (node.initialized && node.patchable) {
                node.methods.change(methodName);
            }

            // Call `satMethod` on each view.

            this.views.forEach(function (view) {
                view.satMethod && view.satMethod(nodeID, methodName, methodHandler);
            });

        }

        this.logger.debugu();

        return methodHandler;
    }

    // -- getMethod ----------------------------------------------------------------------------

    /// @name module:vwf.getMethod
    /// 
    /// @see {@link module:vwf/api/kernel.getMethod}

    getMethod(nodeID, methodName) {

        let self = this;
        this.logger.debuggx("getMethod", function () {
            return [nodeID, methodName];
        });

        var node = this.nodes.existing[nodeID];

        // Call `gettingMethod` on each model. The first model to return a non-undefined value
        // dictates the return value.

        var methodHandler = {};

        this.models.some(function (model) {

            // Call the driver.

            var handler = model.gettingMethod && model.gettingMethod(nodeID, methodName);

            // Update the value to the value assigned if the driver handled it.

            if (handler !== undefined) {
                methodHandler = self.utility.merge({}, handler); // omit `undefined` values
            }

            // Exit the iterator once a driver has handled the retrieval.

            return handler !== undefined;

        });

        // Call `gotMethod` on each view.

        this.views.forEach(function (view) {
            view.gotMethod && view.gotMethod(nodeID, methodName, methodHandler);
        });

        this.logger.debugu();

        return methodHandler;
    }

    // -- callMethod ---------------------------------------------------------------------------

    /// @name module:vwf.callMethod
    /// 
    /// @see {@link module:vwf/api/kernel.callMethod}

    callMethod(nodeID, methodName, methodParameters) {
        let self = this;
        this.logger.debuggx("callMethod", function () {
            return [nodeID, methodName, JSON.stringify(self.loggableValues(methodParameters))];
        });

        // Call callingMethod() on each model. The first model to return a non-undefined value
        // dictates the return value.

        var methodValue = undefined;

        this.models.some(function (model) {
            methodValue = model.callingMethod && model.callingMethod(nodeID, methodName, methodParameters);
            return methodValue !== undefined;
        });

        // Call calledMethod() on each view.

        this.views.forEach(function (view) {
            view.calledMethod && view.calledMethod(nodeID, methodName, methodParameters, methodValue);
        });

        this.logger.debugu();

        return methodValue;
    }

    // -- createEvent --------------------------------------------------------------------------

    /// @name module:vwf.createEvent
    /// 
    /// @see {@link module:vwf/api/kernel.createEvent}

    createEvent(nodeID, eventName, eventParameters) { // TODO: parameters (used? or just for annotation?)  // TODO: allow a handler body here and treat as this.*event* = function() {} (a self-targeted handler); will help with ui event handlers

        this.logger.debuggx("createEvent", nodeID, eventName, eventParameters);

        var node = this.nodes.existing[nodeID];

        // Encode any namespacing into the name. (Namespaced names were added in 0.6.21.)

        var encodedEventName = this.namespaceEncodedName(eventName);

        // Register the event.

        node.events.create(encodedEventName, node.initialized && node.patchable, eventParameters);

        // Call `creatingEvent` on each model. The event is considered created after all models
        // have run.

        this.models.forEach(function (model) {
            model.creatingEvent && model.creatingEvent(nodeID, encodedEventName, eventParameters);
        });

        // Call `createdEvent` on each view. The view is being notified that a event has been
        // created.

        this.views.forEach(function (view) {
            view.createdEvent && view.createdEvent(nodeID, encodedEventName, eventParameters);
        });

        // Send the meta event into the application.

        if (this.models.kernel.enabled()) {
            this.fireEvent(nodeID, ["events", "created"], [eventName]);
        }

        this.logger.debugu();
    }

    // -- setEvent -----------------------------------------------------------------------------

    /// @name module:vwf.setEvent
    /// 
    /// @see {@link module:vwf/api/kernel.setEvent}

    setEvent(nodeID, eventName, eventDescriptor) {

        this.logger.debuggx("setEvent", function () {
            return [nodeID, eventName]; // TODO: loggable eventDescriptor
        });

        var node = this.nodes.existing[nodeID];

        // eventDescriptor = normalizedHandler( eventDescriptor );  // TODO

        // Encode any namespacing into the name.

        var encodedEventName = this.namespaceEncodedName(eventName);

        if (!node.events.hasOwn(encodedEventName)) {

            // If the event doesn't exist on this node, delegate to `kernel.createEvent` to
            // create and assign the event.

            this.createEvent(nodeID, eventName, eventDescriptor.parameters); // TODO: result

            (eventDescriptor.listeners || []).forEach(function (listener) {
                return this.addEventListener(nodeID, eventName, listener, listener.context, listener.phases);
            }, this);

        } else {

            // Locate the event in the registry.

            var event = node.events.existing[encodedEventName];

            // xxx

            eventDescriptor = {

                parameters: event.parameters ?
                    event.parameters.slice() : [], // TODO: note: we're ignoring eventDescriptor.parameters in the set

                listeners: (eventDescriptor.listeners || []).map(function (listener) {

                    if (event.listeners.hasOwn(listener.id)) {
                        return this.setEventListener(nodeID, eventName, listener.id, listener);
                    } else {
                        return this.addEventListener(nodeID, eventName, listener, listener.context, listener.phases);
                    }

                }, this),

            };

        }

        this.logger.debugu();

        return eventDescriptor;
    }

    // -- getEvent -----------------------------------------------------------------------------

    /// @name module:vwf.getEvent
    /// 
    /// @see {@link module:vwf/api/kernel.getEvent}

    getEvent(nodeID, eventName) {

        this.logger.debuggx("getEvent", function () {
            return [nodeID, eventName];
        });

        var node = this.nodes.existing[nodeID];

        // Encode any namespacing into the name.

        var encodedEventName = this.namespaceEncodedName(eventName);

        // Locate the event in the registry.

        var event = node.events.existing[encodedEventName];

        // Build the result descriptor. Omit the `parameters` and `listeners` fields when the
        // parameters or listeners are missing or empty, respectively.

        var eventDescriptor = {};

        if (event.parameters) {
            eventDescriptor.parameters = event.parameters.slice();
        }

        if (event.listeners.existing.length) {
            eventDescriptor.listeners = event.listeners.existing.map(function (eventListenerID) {
                var listener = this.getEventListener(nodeID, eventName, eventListenerID);
                listener.id = eventListenerID;
                return listener;
            }, this);
        }

        this.logger.debugu();

        return eventDescriptor;
    }

    // -- addEventListener ---------------------------------------------------------------------

    /// @name module:vwf.addEventListener
    /// 
    /// @see {@link module:vwf/api/kernel.addEventListener}

    addEventListener(nodeID, eventName, eventHandler, eventContextID, eventPhases) {
        let self = this;
        this.logger.debuggx("addEventListener", function () {
            return [nodeID, eventName, self.loggableScript(eventHandler),
                eventContextID, eventPhases
            ];
        });

        var node = self.nodes.existing[nodeID];

        // Encode any namespacing into the name.

        var encodedEventName = this.namespaceEncodedName(eventName);

        // Register the event if this is the first listener added to an event on a prototype.

        if (!node.events.hasOwn(encodedEventName)) {
            node.events.create(encodedEventName, node.initialized && node.patchable);
        }

        // Locate the event in the registry.

        var event = node.events.existing[encodedEventName];

        // Normalize the descriptor.

        eventHandler = this.normalizedHandler(eventHandler, event.parameters);

        // Register the listener.

        var eventListenerID = eventHandler.id || this.sequence(nodeID);

        event.listeners.create(eventListenerID, node.initialized && node.patchable);

        // Call `addingEventListener` on each model.

        this.models.forEach(function (model) {
            model.addingEventListener &&
                model.addingEventListener(nodeID, encodedEventName, eventListenerID,
                    eventHandler, eventContextID, eventPhases);
        });

        // Call `addedEventListener` on each view.

        this.views.forEach(function (view) {
            view.addedEventListener &&
                view.addedEventListener(nodeID, encodedEventName, eventListenerID,
                    eventHandler, eventContextID, eventPhases);
        });

        this.logger.debugu();

        return eventListenerID;
    }

    // -- removeEventListener ------------------------------------------------------------------

    /// @name module:vwf.removeEventListener
    /// 
    /// @see {@link module:vwf/api/kernel.removeEventListener}

    removeEventListener(nodeID, eventName, eventListenerID) {
        let self = this;
        this.logger.debuggx("removeEventListener", function () {
            return [nodeID, eventName, self.loggableScript(eventListenerID)];
        });

        var node = this.nodes.existing[nodeID];

        // Encode any namespacing into the name.

        var encodedEventName = this.namespaceEncodedName(eventName);

        // Locate the event in the registry.

        var event = node.events.existing[encodedEventName];

        // Unregister the listener.

        event.listeners.delete(eventListenerID, node.initialized && node.patchable);

        // Call `removingEventListener` on each model.

        this.models.forEach(function (model) {
            model.removingEventListener &&
                model.removingEventListener(nodeID, encodedEventName, eventListenerID);
        });

        // Call `removedEventListener` on each view.

        this.views.forEach(function (view) {
            view.removedEventListener &&
                view.removedEventListener(nodeID, encodedEventName, eventListenerID);
        });

        this.logger.debugu();

        return eventListenerID;
    }

    // -- setEventListener ---------------------------------------------------------------------

    /// @name module:vwf.setEventListener
    /// 
    /// @see {@link module:vwf/api/kernel.setEventListener}

    setEventListener(nodeID, eventName, eventListenerID, eventListener) {

        let self = this;
        this.logger.debuggx("setEventListener", function () {
            return [nodeID, eventName, eventListenerID]; // TODO: loggable eventListener
        });

        var node = this.nodes.existing[nodeID];

        // Encode any namespacing into the name.

        var encodedEventName = this.namespaceEncodedName(eventName);

        // Locate the event in the registry.

        var event = node.events.existing[encodedEventName];

        // Normalize the descriptor.

        eventListener = this.normalizedHandler(eventListener, event.parameters);

        // Record the change.

        if (node.initialized && node.patchable) {
            event.listeners.change(eventListenerID);
        }

        // Call `settingEventListener` on each model. The first model to return a non-undefined
        // value dictates the return value.

        this.models.some(function (model) {

            // Call the driver.

            var listener = model.settingEventListener &&
                model.settingEventListener(nodeID, encodedEventName, eventListenerID, eventListener);

            // Update the value to the value assigned if the driver handled it.

            if (listener !== undefined) {
                eventListener = self.utility.merge({}, listener); // omit `undefined` values
            }

            // Exit the iterator once a driver has handled the assignment.

            return listener !== undefined;

        });

        // Call `satEventListener` on each view.

        this.views.forEach(function (view) {
            view.satEventListener &&
                view.satEventListener(nodeID, encodedEventName, eventListenerID, eventListener);
        });

        this.logger.debugu();

        return eventListener;
    }

    // -- getEventListener ---------------------------------------------------------------------

    /// @name module:vwf.getEventListener
    /// 
    /// @see {@link module:vwf/api/kernel.getEventListener}

    getEventListener(nodeID, eventName, eventListenerID) {

        let self = this;
        this.logger.debuggx("getEventListener", function () {
            return [nodeID, eventName, eventListenerID];
        });

        // Encode any namespacing into the name.

        var encodedEventName = this.namespaceEncodedName(eventName);

        // Call `gettingEventListener` on each model. The first model to return a non-undefined
        // value dictates the return value.

        var eventListener = {};

        this.models.some(function (model) {

            // Call the driver.

            var listener = model.gettingEventListener &&
                model.gettingEventListener(nodeID, encodedEventName, eventListenerID);

            // Update the value to the value assigned if the driver handled it.

            if (listener !== undefined) {
                eventListener = self.utility.merge({}, listener); // omit `undefined` values
            }

            // Exit the iterator once a driver has handled the assignment.

            return listener !== undefined;

        });

        // Call `gotEventListener` on each view.

        this.views.forEach(function (view) {
            view.gotEventListener &&
                view.gotEventListener(nodeID, encodedEventName, eventListenerID, eventListener);
        });

        this.logger.debugu();

        return eventListener;
    }

    // -- flushEventListeners ------------------------------------------------------------------

    /// @name module:vwf.flushEventListeners
    /// 
    /// @see {@link module:vwf/api/kernel.flushEventListeners}

    flushEventListeners(nodeID, eventName, eventContextID) {

        this.logger.debuggx("flushEventListeners", nodeID, eventName, eventContextID);

        // Encode any namespacing into the name.

        var encodedEventName = this.namespaceEncodedName(eventName);

        // Retrieve the event in case we need to remove listeners from it

        var node = this.nodes.existing[nodeID];
        var event = node.events.existing[encodedEventName];

        // Call `flushingEventListeners` on each model.

        this.models.forEach(function (model) {
            var removedIds = model.flushingEventListeners &&
                model.flushingEventListeners(nodeID, encodedEventName, eventContextID);

            // If the model driver returned an array of the ids of event listeners that it 
            // removed, remove their references in the kernel

            if (removedIds && removedIds.length) {

                // Unregister the listeners that were flushed
                removedIds.forEach(function (removedId) {
                    event.listeners.delete(removedId, node.initialized && node.patchable);
                });
            }
        });

        // Call `flushedEventListeners` on each view.

        this.views.forEach(function (view) {
            view.flushedEventListeners &&
                view.flushedEventListeners(nodeID, encodedEventName, eventContextID);
        });

        // TODO: `flushEventListeners` can be interpreted by the kernel now and handled with a
        // `removeEventListener` call instead of separate `flushingEventListeners` and
        // `flushedEventListeners` calls to the drivers.

        this.logger.debugu();
    }

    // -- fireEvent ----------------------------------------------------------------------------

    /// @name module:vwf.fireEvent
    /// 
    /// @see {@link module:vwf/api/kernel.fireEvent}

    fireEvent(nodeID, eventName, eventParameters) {
        let self = this;
        this.logger.debuggx("fireEvent", function () {
            return [nodeID, eventName, JSON.stringify(self.loggableValues(eventParameters))];
        });

        // Encode any namespacing into the name. (Namespaced names were added in 0.6.21.)

        var encodedEventName = this.namespaceEncodedName(eventName);

        // Call `firingEvent` on each model.

        var handled = this.models.reduce(function (handled, model) {
            return model.firingEvent && model.firingEvent(nodeID, encodedEventName, eventParameters) || handled;
        }, false);

        // Call `firedEvent` on each view.

        this.views.forEach(function (view) {
            view.firedEvent && view.firedEvent(nodeID, encodedEventName, eventParameters);
        });

        this.logger.debugu();

        // TODO: `fireEvent` needs to tell the drivers to invoke each listener individually
        // now that listeners can be spread across multiple drivers.

        return handled;
    }

    // -- dispatchEvent ------------------------------------------------------------------------

    /// Dispatch an event toward a node. Using fireEvent(), capture (down) and bubble (up) along
    /// the path from the global root to the node. Cancel when one of the handlers returns a
    /// truthy value to indicate that it has handled the event.
    /// 
    /// @name module:vwf.dispatchEvent
    /// 
    /// @see {@link module:vwf/api/kernel.dispatchEvent}

    dispatchEvent(nodeID, eventName, eventParameters, eventNodeParameters) {
        let self = this;
        this.logger.debuggx("dispatchEvent", function () {
            return [nodeID, eventName, JSON.stringify(self.loggableValues(eventParameters)),
                JSON.stringify(self.loggableIndexedValues(eventNodeParameters))
            ];
        });

        // Defaults for the parameters to send with the events. Values from `eventParameters`
        // are sent to each node. `eventNodeParameters` contains additional values to send to
        // specific nodes.

        eventParameters = eventParameters || [];
        eventNodeParameters = eventNodeParameters || {};

        // Find the inheritance path from the node to the root.

        var ancestorIDs = this.ancestors(nodeID);
        var lastAncestorID = "";

        // Make space to record the parameters sent to each node. Parameters provided for upper
        // nodes cascade down until another definition is found for a lower node. We'll remember
        // these on the way down and replay them on the way back up.

        var cascadedEventNodeParameters = {
            "": eventNodeParameters[""] || [] // defaults come from the "" key in eventNodeParameters
        };

        // Parameters passed to the handlers are the concatention of the eventParameters array,
        // the eventNodeParameters for the node (cascaded), and the phase.

        var targetEventParameters = undefined;

        var phase = undefined;
        var handled = false;

        // Capturing phase.

        phase = "capture"; // only handlers tagged "capture" will be invoked

        handled = handled || ancestorIDs.reverse().some(function (ancestorID) { // TODO: reverse updates the array in place every time and we'd rather not

            cascadedEventNodeParameters[ancestorID] = eventNodeParameters[ancestorID] ||
                cascadedEventNodeParameters[lastAncestorID];

            lastAncestorID = ancestorID;

            targetEventParameters =
                eventParameters.concat(cascadedEventNodeParameters[ancestorID], phase);

            targetEventParameters.phase = phase; // smuggle the phase across on the parameters array  // TODO: add "phase" as a fireEvent() parameter? it isn't currently needed in the kernel public API (not queueable, not called by the drivers), so avoid if possible

            return this.fireEvent(ancestorID, eventName, targetEventParameters);

        }, this);

        // At target.

        phase = undefined; // invoke all handlers

        cascadedEventNodeParameters[nodeID] = eventNodeParameters[nodeID] ||
            cascadedEventNodeParameters[lastAncestorID];

        targetEventParameters =
            eventParameters.concat(cascadedEventNodeParameters[nodeID], phase);

        handled = handled || this.fireEvent(nodeID, eventName, targetEventParameters);

        // Bubbling phase.

        phase = undefined; // invoke all handlers

        handled = handled || ancestorIDs.reverse().some(function (ancestorID) { // TODO: reverse updates the array in place every time and we'd rather not

            targetEventParameters =
                eventParameters.concat(cascadedEventNodeParameters[ancestorID], phase);

            return this.fireEvent(ancestorID, eventName, targetEventParameters);

        }, this);

        this.logger.debugu();
    }

    // -- execute ------------------------------------------------------------------------------

    /// @name module:vwf.execute
    /// 
    /// @see {@link module:vwf/api/kernel.execute}

    execute(nodeID, scriptText, scriptType, callback_async /* result */) {

        let self = this;

        this.logger.debuggx("execute", function () {
            return [nodeID, self.loggableScript(scriptText), scriptType];
        });

        // Assume JavaScript if the type is not specified and the text is a string.

        if (!scriptType && (typeof scriptText == "string" || scriptText instanceof String)) {
            scriptType = "application/javascript";
        }

        // Call executing() on each model. The script is considered executed after all models
        // have run.

        var scriptValue = undefined;

        // Watch for any async kernel calls generated as we execute the scriptText and wait for
        // them to complete before calling the callback.

        self.models.kernel.capturingAsyncs(function () {
            self.models.some(function (model) {
                scriptValue = model.executing &&
                    model.executing(nodeID, scriptText, scriptType);
                return scriptValue !== undefined;
            });

            // Call executed() on each view to notify view that a script has been executed.

            self.views.forEach(function (view) {
                view.executed && view.executed(nodeID, scriptText, scriptType);
            });

        }, function () {
            callback_async && callback_async(scriptValue);
        });

        this.logger.debugu();

        return scriptValue;
    }

    // -- random -------------------------------------------------------------------------------

    /// @name module:vwf.random
    /// 
    /// @see {@link module:vwf/api/kernel.random}

    random(nodeID) {
        return this.models.object.random(nodeID);
    }

    // -- seed ---------------------------------------------------------------------------------

    /// @name module:vwf.seed
    /// 
    /// @see {@link module:vwf/api/kernel.seed}

    seed(nodeID, seed) {
        return this.models.object.seed(nodeID, seed);
    }

    // -- time ---------------------------------------------------------------------------------

    /// The current simulation time.
    /// 
    /// @name module:vwf.time
    /// 
    /// @see {@link module:vwf/api/kernel.time}

    now() {
        return this.virtualTime.now;
    }

    time() {
        return this.virtualTime.now;
    }

    // -- client -------------------------------------------------------------------------------

    /// The moniker of the client responsible for the current action. Will be falsy for actions
    /// originating in the server, such as time ticks.
    /// 
    /// @name module:vwf.client
    /// 
    /// @see {@link module:vwf/api/kernel.client}

    client() {
        return this.virtualTime.client_;
    }

    // -- moniker ------------------------------------------------------------------------------

    /// The identifer the server assigned to this client.
    /// 
    /// @name module:vwf.moniker
    /// 
    /// @see {@link module:vwf/api/kernel.moniker}

    moniker() {
        return this.moniker_;
    }

    // -- application --------------------------------------------------------------------------

    /// @name module:vwf.application
    /// 
    /// @see {@link module:vwf/api/kernel.application}

    application(initializedOnly) {
        let self = this;
        var applicationID;

        Object.keys(self.nodes.globals).forEach(function (globalID) {
            var global = self.nodes.existing[globalID];
            if ((!initializedOnly || global.initialized) && global.name === "application") {
                applicationID = globalID;
            }
        }, this);

        return applicationID;
    }

    // -- intrinsics ---------------------------------------------------------------------------

    /// @name module:vwf.intrinsics
    /// 
    /// @see {@link module:vwf/api/kernel.intrinsics}

    intrinsics(nodeID, result) {
        return this.models.object.intrinsics(nodeID, result);
    }

    // -- uri ----------------------------------------------------------------------------------

    /// @name module:vwf.uri
    /// 
    /// @see {@link module:vwf/api/kernel.uri}

    uri(nodeID, searchAncestors, initializedOnly) {

        var uri = this.models.object.uri(nodeID);

        if (searchAncestors) {
            while (!uri && (nodeID = this.parent(nodeID, initializedOnly))) {
                uri = this.models.object.uri(nodeID);
            }
        }

        return uri;
    }

    // -- name ---------------------------------------------------------------------------------

    /// @name module:vwf.name
    /// 
    /// @see {@link module:vwf/api/kernel.name}

    name(nodeID) {
        return this.models.object.name(nodeID);
    }

    // -- prototype ----------------------------------------------------------------------------

    /// @name module:vwf.prototype
    /// 
    /// @see {@link module:vwf/api/kernel.prototype}

    prototype(nodeID) {
        return this.models.object.prototype(nodeID);
    }

    // -- prototypes ---------------------------------------------------------------------------

    /// @name module:vwf.prototypes
    /// 
    /// @see {@link module:vwf/api/kernel.prototypes}

    prototypes(nodeID, includeBehaviors) {

        var prototypes = [];

        do {

            // Add the current node's behaviors.
            if (includeBehaviors) {
                var b = [].concat(this.behaviors(nodeID));
                Array.prototype.push.apply(prototypes, b.reverse());
            }

            // Get the next prototype.
            nodeID = this.prototype(nodeID);

            // Add the prototype.
            if (nodeID) {
                prototypes.push(nodeID);
            }

        } while (nodeID);

        return prototypes;
    }

    // -- behaviors ----------------------------------------------------------------------------

    /// @name module:vwf.behaviors
    /// 
    /// @see {@link module:vwf/api/kernel.behaviors}

    behaviors(nodeID) {
        return this.models.object.behaviors(nodeID);
    }

    // -- globals ------------------------------------------------------------------------------

    /// @name module:vwf.globals
    /// 
    /// @see {@link module:vwf/api/kernel.globals}

    globals(initializedOnly) {
        let self = this;
        var globals = {};

        Object.keys(self.nodes.globals).forEach(function (globalID) {
            if (!initializedOnly || self.nodes.existing[globalID].initialized) {
                globals[globalID] = undefined;
            }
        }, this);

        return globals;
    }

    // -- global -------------------------------------------------------------------------------

    /// @name module:vwf.global
    /// 
    /// @see {@link module:vwf/api/kernel.global}

    global(globalReference, initializedOnly) {

        let self = this;
        var globals = this.globals(initializedOnly);

        // Look for a global node whose URI matches `globalReference`. If there is no match by
        // URI, then search again by name.

        return matches("uri") || matches("name");

        // Look for a global node where the field named by `field` matches `globalReference`.

        function matches(field) {

            var matchingID;

            Object.keys(globals).some(function (globalID) {
                if (self.nodes.existing[globalID][field] === globalReference) {
                    matchingID = globalID;
                    return true;
                }
            });

            return matchingID;
        }

    }



    // -- root ---------------------------------------------------------------------------------

    /// @name module:vwf.root
    /// 
    /// @see {@link module:vwf/api/kernel.root}

    root(nodeID, initializedOnly) {

        var rootID;

        // Walk the ancestors to the top of the tree. Stop when we reach the pseudo-node at the
        // global root, which unlike all other nodes has a falsy ID, or `undefined` if we could
        // not reach the top because `initializedOnly` is set and we attempted to cross between
        // nodes that have and have not completed initialization.

        do {
            rootID = nodeID;
            nodeID = this.parent(nodeID, initializedOnly);
        } while (nodeID);

        // Return the root ID, or `undefined` when `initializedOnly` is set and the node can't
        // see the root.

        return nodeID === undefined ? undefined : rootID;
    }

    // -- ancestors ----------------------------------------------------------------------------

    /// @name module:vwf.ancestors
    /// 
    /// @see {@link module:vwf/api/kernel.ancestors}

    ancestors(nodeID, initializedOnly) {

        var ancestors = [];

        nodeID = this.parent(nodeID, initializedOnly);

        while (nodeID) {
            ancestors.push(nodeID);
            nodeID = this.parent(nodeID, initializedOnly);
        }

        return ancestors;
    }

    // -- parent -------------------------------------------------------------------------------

    /// @name module:vwf.parent
    /// 
    /// @see {@link module:vwf/api/kernel.parent}

    parent(nodeID, initializedOnly) {
        return this.models.object.parent(nodeID, initializedOnly);
    }

    // -- children -----------------------------------------------------------------------------

    /// @name module:vwf.children
    /// 
    /// @see {@link module:vwf/api/kernel.children}

    children(nodeID, initializedOnly) {

        if (nodeID === undefined) {
            this.logger.errorx("children", "cannot retrieve children of nonexistent node");
            return;
        }

        return this.models.object.children(nodeID, initializedOnly);
    }

    // -- child --------------------------------------------------------------------------------

    /// @name module:vwf.child
    /// 
    /// @see {@link module:vwf/api/kernel.child}

    child(nodeID, childReference, initializedOnly) {

        var children = this.children(nodeID, initializedOnly);

        if (typeof childReference === "number" || childReference instanceof Number) {
            return children[childReference];
        } else {
            return children.filter(function (childID) {
                return childID && this.name(childID) === childReference;
            }, this)[0];
        }

    }

    // -- descendants --------------------------------------------------------------------------

    /// @name module:vwf.descendants
    /// 
    /// @see {@link module:vwf/api/kernel.descendants}

    descendants(nodeID, initializedOnly) {

        if (nodeID === undefined) {
            this.logger.errorx("descendants", "cannot retrieve children of nonexistent node");
            return;
        }

        var descendants = [];

        this.children(nodeID, initializedOnly).forEach(function (childID) {
            descendants.push(childID);
            childID && Array.prototype.push.apply(descendants, this.descendants(childID, initializedOnly));
        }, this);

        return descendants;
    }

    // -- sequence -----------------------------------------------------------------------------

    /// @name module:vwf.sequence
    /// 
    /// @see {@link module:vwf/api/kernel.sequence}

    sequence(nodeID) {
        return this.models.object.sequence(nodeID);
    }


    /// Locate nodes matching a search pattern. See vwf.api.kernel#find for details.
    /// 
    /// @name module:vwf.find
    ///
    /// @param {ID} nodeID
    ///   The reference node. Relative patterns are resolved with respect to this node. `nodeID`
    ///   is ignored for absolute patterns.
    /// @param {String} matchPattern
    ///   The search pattern.
    /// @param {Boolean} [initializedOnly]
    ///   Interpret nodes that haven't completed initialization as though they don't have
    ///   ancestors. Drivers that manage application code should set `initializedOnly` since
    ///   applications should never have access to uninitialized parts of the application graph.
    /// @param {Function} [callback]
    ///   A callback to receive the search results. If callback is provided, find invokes
    ///   callback( matchID ) for each match. Otherwise the result is returned as an array.
    /// 
    /// @returns {ID[]|undefined}
    ///   If callback is provided, undefined; otherwise an array of the node ids of the result.
    /// 
    /// @see {@link module:vwf/api/kernel.find}

    find(nodeID, matchPattern, initializedOnly, callback /* ( matchID ) */) {

        // Interpret `find( nodeID, matchPattern, callback )` as
        // `find( nodeID, matchPattern, undefined, callback )`. (`initializedOnly` was added in
        // 0.6.8.)

        if (typeof initializedOnly == "function" || initializedOnly instanceof Function) {
            callback = initializedOnly;
            initializedOnly = undefined;
        }

        // Run the query.

        var matchIDs = find.call(this, nodeID, matchPattern, initializedOnly);

        // Return the result. Invoke the callback if one was provided. Otherwise, return the
        // array directly.

        if (callback) {

            matchIDs.forEach(function (matchID) {
                callback(matchID);
            });

        } else { // TODO: future iterator proxy

            return matchIDs;
        }

    }

    // -- findClients ------------------------------------------------------------------------------

    /// Locate client nodes matching a search pattern. 
    ///
    /// @name module:vwf.findClients
    ///
    /// @param {ID} nodeID
    ///   The reference node. Relative patterns are resolved with respect to this node. `nodeID`
    ///   is ignored for absolute patterns.
    /// @param {String} matchPattern
    ///   The search pattern.
    /// @param {Function} [callback]
    ///   A callback to receive the search results. If callback is provided, find invokes
    ///   callback( matchID ) for each match. Otherwise the result is returned as an array.
    /// 
    /// @returns {ID[]|undefined}
    ///   If callback is provided, undefined; otherwise an array of the node ids of the result.
    /// 
    /// @deprecated in version 0.6.21. Instead of `kernel.findClients( reference, "/pattern" )`,
    ///   use `kernel.find( reference, "doc('http://vwf.example.com/clients.vwf')/pattern" )`.
    /// 
    /// @see {@link module:vwf/api/kernel.findClients}

    findClients(nodeID, matchPattern, callback /* ( matchID ) */) {

        this.logger.warn("`kernel.findClients` is deprecated. Use " +
            "`kernel.find( nodeID, \"doc('proxy/clients.vwf')/pattern\" )`" +
            " instead.");

        var clientsMatchPattern = "doc('proxy/clients.vwf')" +
            (matchPattern[0] === "/" ? "" : "/") + matchPattern;

        return this.find(nodeID || this.application(), clientsMatchPattern, callback);
    }

    /// Test a node against a search pattern. See vwf.api.kernel#test for details.
    /// 
    /// @name module:vwf.test
    /// 
    /// @param {ID} nodeID
    ///   The reference node. Relative patterns are resolved with respect to this node. `nodeID`
    ///   is ignored for absolute patterns.
    /// @param {String} matchPattern
    ///   The search pattern.
    /// @param {ID} testID
    ///   A node to test against the pattern.
    /// @param {Boolean} [initializedOnly]
    ///   Interpret nodes that haven't completed initialization as though they don't have
    ///   ancestors. Drivers that manage application code should set `initializedOnly` since
    ///   applications should never have access to uninitialized parts of the application graph.
    /// 
    /// @returns {Boolean}
    ///   true when testID matches the pattern.
    /// 
    /// @see {@link module:vwf/api/kernel.test}

    test(nodeID, matchPattern, testID, initializedOnly) {

        // Run the query.

        var matchIDs = this.find.call(this, nodeID, matchPattern, initializedOnly);

        // Search for the test node in the result.

        return matchIDs.some(function (matchID) {
            return matchID == testID;
        });

    }


    // == Private functions ====================================================================

    // -- loadComponent ------------------------------------------------------------------------

    /// @name module:vwf~loadComponent

    loadComponent(nodeURI, baseURI, callback_async /* nodeDescriptor */, errback_async /* errorMessage */) { // TODO: turn this into a generic xhr loader exposed as a kernel function?

        let self = this;

        if (nodeURI == self.kutility.protoNodeURI) {

            callback_async(self.kutility.protoNodeDescriptor);

        } else if (nodeURI.match(RegExp("^data:application/json;base64,"))) {

            // Primarly for testing, parse one specific form of data URIs. We need to parse
            // these ourselves since Chrome can't load data URIs due to cross origin
            // restrictions.

            callback_async(JSON.parse(atob(nodeURI.substring(29)))); // TODO: support all data URIs

        } else {

            self.virtualTime.suspend("while loading " + nodeURI); // suspend the queue

            let fetchUrl = self.remappedURI(nodeURI, baseURI);
            let dbName = fetchUrl.split(".").join("_");

            const parseComp = function (f) {

                let result = JSON.parse(f);

                let nativeObject = result;
                // console.log(nativeObject);

                if (nativeObject) {
                    callback_async(nativeObject);
                    self.virtualTime.resume("after loading " + nodeURI); // resume the queue; may invoke dispatch(), so call last before returning to the host

                } else {

                    self.logger.warnx("loadComponent", "error loading", nodeURI + ":", error);
                    errback_async(error);
                    self.virtualTime.resume("after loading " + nodeURI); // resume the queue; may invoke dispatch(), so call last before returning to the host
                }

            }


            //var fileName = "";
            // let userDB = _LCSDB.user(_LCS_WORLD_USER.pub);    
            if (dbName.includes("proxy")) {
                //userDB = await window._LCS_SYS_USER.get('proxy').then();
                let proxyDB = self.proxy ? _LCSDB.user(self.proxy) : _LCSDB.user(_LCS_WORLD_USER.pub);
                let fileName = dbName + '_json';
                let dbNode = proxyDB.get('proxy').get(fileName);
                let nodeProm = new Promise(res => dbNode.once(res));

                nodeProm.then(comp => {
                    parseComp(comp);
                })

                //    (function(r){
                //        //console.log(r);
                //        parseComp(r);

                //    });

            } else {
                var worldName = dbName.split('/')[1];
                var fileName = dbName.split('/')[2];
                //+ '_json';

                if (!fileName) {
                    worldName = self.helpers.appPath
                    fileName = dbName + '_json';
                } else {
                    fileName = fileName + '_json';
                }

                let dbNode = _LCSDB.user(_LCS_WORLD_USER.pub).get('worlds').path(worldName).get(fileName);

                let nodeProm = new Promise(res => dbNode.once(res))
                nodeProm.then(comp => {
                    parseComp(comp);
                })

                //    (function(r){
                //     //console.log(r);
                //     parseComp(r);

                // });
            }

            //console.log(source);

            //userDB.get(fileName).once(async function(res) {




            // }, {wait: 1000})
        }

    }

    // -- loadScript ---------------------------------------------------------------------------

    /// @name module:vwf~loadScript

    loadScript(scriptURI, baseURI, callback_async /* scriptText */, errback_async /* errorMessage */) {

        let self = this;
        if (scriptURI.match(RegExp("^data:application/javascript;base64,"))) {

            // Primarly for testing, parse one specific form of data URIs. We need to parse
            // these ourselves since Chrome can't load data URIs due to cross origin
            // restrictions.

            callback_async(atob(scriptURI.substring(35))); // TODO: support all data URIs

        } else {

            self.virtualTime.suspend("while loading " + scriptURI); // suspend the queue

            let fetchUrl = self.remappedURI(scriptURI, baseURI);
            let dbName = fetchUrl.split(".").join("_")

            const parseComp = function (res) {

                let scriptText = res;

                try {
                    callback_async(scriptText);
                    self.virtualTime.resume("after loading " + scriptURI); // resume the queue; may invoke dispatch(), so call last before returning to the host

                } catch (e) {

                    self.logger.warnx("loadScript", "error loading", scriptURI + ":", error);
                    errback_async(error);
                    self.virtualTime.resume("after loading " + scriptURI); // resume the queue; may invoke dispatch(), so call last before returning to the host
                }
            }



            var worldName = dbName.split('/')[1];
            //let userDB = _LCSDB.user(_LCS_WORLD_USER.pub);  


            if (dbName.includes("proxy")) {
                let proxyDB = self.proxy ? _LCSDB.user(self.proxy) : _LCSDB.user(_LCS_WORLD_USER.pub);

             
                
                let url = scriptURI.startsWith('/') ? scriptURI.substring(1) : fetchUrl;
                let scrName = scriptURI.startsWith('/') ? url.split(".").join("_") : dbName;

                //userDB = window._LCS_SYS_USER.get('proxy');
                let fileName = scrName;
                let dbNode = proxyDB.get('proxy').get(fileName);
                let nodeProm = new Promise(res => dbNode.once(res))

                nodeProm.then(comp => {
                    parseComp(comp);
                })
                // window._LCS_SYS_USER.get('proxy').get(fileName).get('file').once(function(r){
                //     //console.log(r);
                //     parseComp(r);
                // });

            } else {
                var fileName = dbName.split('/')[2]; //dbName.replace(worldName + '/', "");

                if (!fileName) {
                    worldName = self.helpers.appPath
                    fileName = dbName;
                } else {
                    fileName = fileName;
                }


                let dbNode = _LCSDB.user(_LCS_WORLD_USER.pub).get('worlds').path(worldName).get(fileName);
                let nodeProm = new Promise(res => dbNode.once(res))
                nodeProm.then(comp => {
                    parseComp(comp);
                })
                // userDB.get('worlds').path(worldName).get(fileName).get('file').once(function(r){
                //     //console.log(r);
                //     parseComp(r);

                // });
            }

            // userDB.get(fileName).once(, {wait: 1000})
        }

    }



    /// Determine if a given property of a node has a setter function, either directly on the
    /// node or inherited from a prototype.
    /// 
    /// This function must run as a method of the kernel. Invoke as: nodePropertyHasSetter.call(
    ///   kernel, nodeID, propertyName ).
    /// 
    /// @name module:vwf~nodePropertyHasSetter
    /// 
    /// @param {ID} nodeID
    /// @param {String} propertyName
    /// 
    /// @returns {Boolean}

    nodePropertyHasSetter(nodeID, propertyName) { // invoke with the kernel as "this"  // TODO: this is peeking inside of vwf-model-javascript; need to delegate to all script drivers
        var node = this.models.javascript.nodes[nodeID];
        var setter = node.private.setters && node.private.setters[propertyName];
        return typeof setter == "function" || setter instanceof Function;
    }

    /// Determine if a given property of a node has a setter function. The node's prototypes are
    /// not considered.
    /// 
    /// This function must run as a method of the kernel. Invoke as:
    ///   nodePropertyHasOwnSetter.call( kernel, nodeID, propertyName ).
    /// 
    /// @name module:vwf~nodePropertyHasOwnSetter
    /// 
    /// @param {ID} nodeID
    /// @param {String} propertyName
    /// 
    /// @returns {Boolean}

    nodePropertyHasOwnSetter(nodeID, propertyName) { // invoke with the kernel as "this"  // TODO: this is peeking inside of vwf-model-javascript; need to delegate to all script drivers
        var node = this.models.javascript.nodes[nodeID];
        var setter = node.private.setters && node.private.setters.hasOwnProperty(propertyName) && node.private.setters[propertyName];
        return typeof setter == "function" || setter instanceof Function;
    }

    /// Determine if a node has a child with the given name, either directly on the node or
    /// inherited from a prototype.
    /// 
    /// This function must run as a method of the kernel. Invoke as: nodeHasChild.call(
    ///   kernel, nodeID, childName ).
    /// 
    /// @name module:vwf~nodeHasChild
    /// 
    /// @param {ID} nodeID
    /// @param {String} childName
    /// 
    /// @returns {Boolean}

    nodeHasChild(nodeID, childName) { // invoke with the kernel as "this"  // TODO: this is peeking inside of vwf-model-javascript
        var node = this.models.javascript.nodes[nodeID];
        return childName in node.children;
    }

    /// Determine if a node has a child with the given name. The node's prototypes are not
    /// considered.
    /// 
    /// This function must run as a method of the kernel. Invoke as: nodeHasOwnChild.call(
    ///   kernel, nodeID, childName ).
    /// 
    /// @name module:vwf~nodeHasOwnChild
    /// 
    /// @param {ID} nodeID
    /// @param {String} childName
    /// 
    /// @returns {Boolean}

    nodeHasOwnChild(nodeID, childName) { // invoke with the kernel as "this"  // TODO: this is peeking inside of vwf-model-javascript
        var node = this.models.javascript.nodes[nodeID];
        var hasChild = false;
        if (parseInt(childName).toString() !== childName) {
            hasChild = node.children.hasOwnProperty(childName); // TODO: this is peeking inside of vwf-model-javascript
        } else {
            // Children with numeric names do not get added as properties of the children array, so loop over the children
            // to check manually
            for (var i = 0, il = node.children.length; i < il; i++) {
                if (childName === node.children[i].name) {
                    hasChild = true;
                }
            }
        }
        return hasChild;
    }

    /// Determine if a component specifier is a URI.
    /// 
    /// A component may be specified as the URI of a resource containing a descriptor (string),
    /// a descriptor (object), or the ID of a previously-created node (primitive).
    /// 
    /// @name module:vwf~componentIsURI
    /// 
    /// @param {String|Object} candidate
    /// 
    /// @returns {Boolean}

    componentIsURI(candidate) {
        return (typeof candidate == "string" || candidate instanceof String) && !this.componentIsID(candidate);
    }

    /// Determine if a component specifier is a descriptor.
    /// 
    /// A component may be specified as the URI of a resource containing a descriptor (string),
    /// a descriptor (object), or the ID of a previously-created node (primitive).
    /// 
    /// @name module:vwf~componentIsDescriptor
    /// 
    /// @param {String|Object} candidate
    /// 
    /// @returns {Boolean}

    componentIsDescriptor(candidate) {
        return typeof candidate == "object" && candidate != null && !this.isPrimitive(candidate);
    }

    /// Determine if a component specifier is an ID.
    /// 
    /// A component may be specified as the URI of a resource containing a descriptor (string),
    /// a descriptor (object), or the ID of a previously-created node (primitive).
    /// 
    /// @name module:vwf~componentIsID
    /// 
    /// @param {String|Object} candidate
    /// 
    /// @returns {Boolean}

    componentIsID(candidate) {
        return this.isPrimitive(candidate) && this.models.object.exists(candidate) &&
            !(this.components[candidate] instanceof Array);
    }

    /// Determine if a value is a JavaScript primitive, or the boxed version of a JavaScript
    /// primitive.
    /// 
    /// Node IDs are JavaScript primitives. This function may be used to determine if a value
    /// has the correct type to be a node ID.
    /// 
    /// @name module:vwf~isPrimitive
    /// 
    /// @param candidate
    /// 
    /// @returns {Boolean}

    isPrimitive(candidate) {

        switch (typeof candidate) {

            case "string":
            case "number":
            case "boolean":
                return true;

            case "object":
                return candidate instanceof String || candidate instanceof Number ||
                    candidate instanceof Boolean;

            default:
                return false;

        }

    }

    /// Determine if an object is a component descriptor. Detect the type by searching for
    /// descriptor keys in the candidate object.
    /// 
    /// @name module:vwf~objectIsComponent
    /// 
    /// @param {Object} candidate
    /// 
    /// @returns {Boolean}

    objectIsComponent(candidate) {

        var componentAttributes = [
            "extends",
            "implements",
            "source",
            "type",
            "properties",
            "methods",
            "events",
            "children",
            "scripts",
        ];

        var isComponent = false;

        if (typeof candidate == "object" && candidate != null) {

            isComponent = componentAttributes.some(function (attributeName) {
                return candidate.hasOwnProperty(attributeName);
            });

        }

        return isComponent;
    }

    /// Determine if a property initializer is a detailed initializer containing explicit
    /// accessor and value parameters (rather than a simple value specification). Detect the
    /// type by searching for property initializer keys in the candidate object.
    /// 
    /// @name module:vwf~valueHasAccessors
    /// 
    /// @param {Object} candidate
    /// 
    /// @returns {Boolean}

    valueHasAccessors(candidate) {

        var accessorAttributes = [
            "get",
            "set",
            "value",
            "node",
            "create",
            "undefined",
        ];

        var hasAccessors = false;

        if (typeof candidate == "object" && candidate != null) {

            hasAccessors = accessorAttributes.some(function (attributeName) {
                return candidate.hasOwnProperty(attributeName);
            });

        }

        return hasAccessors;
    }

    /// Determine if a method or event initializer is a detailed initializer containing a
    /// parameter list along with the body text (method initializers only). Detect the type by
    /// searching for method and event initializer keys in the candidate object.
    /// 
    /// @name module:vwf~valueHasBody
    /// 
    /// @param {Object} candidate
    /// 
    /// @returns {Boolean}

    valueHasBody(candidate) { // TODO: refactor and share with valueHasAccessors and possibly objectIsComponent  // TODO: unlike a property initializer, we really only care if it's an object vs. text; text == use as body; object == presume o.parameters and o.body  // TODO: except that a script in the unnamed-list format would appear as an object but should be used as the body

        var bodyAttributes = [
            "parameters",
            "body",
            "listeners",
        ];

        var hasBody = false; // TODO: "body" term is confusing, but that's the current terminology used in vwf/model/javascript

        if (typeof candidate == "object" && candidate != null) {

            hasBody = bodyAttributes.some(function (attributeName) {
                return candidate.hasOwnProperty(attributeName);
            });

        }

        return hasBody;
    }

    /// Determine if a script initializer is a detailed initializer containing explicit text and
    /// type parameters (rather than being a simple text specification). Detect the type by
    /// searching for the script initializer keys in the candidate object.
    /// 
    /// @name module:vwf~valueHasType
    /// 
    /// @param {Object} candidate
    /// 
    /// @returns {Boolean}

    valueHasType(candidate) { // TODO: refactor and share with valueHasBody, valueHasAccessors and possibly objectIsComponent

        var typeAttributes = [
            "source",
            "text",
            "type",
        ];

        var hasType = false;

        if (typeof candidate == "object" && candidate != null) {

            hasType = typeAttributes.some(function (attributeName) {
                return candidate.hasOwnProperty(attributeName);
            });

        }

        return hasType;
    }

    /// Convert a potentially-namespaced member name into a string such that a namespaced name
    /// will be distinct from an encoded name in any other namespace, or from any simple name
    /// not having a namespace.
    /// 
    /// Simple names are strings such as `"name"`. Namespaced names are arrays of strings, such
    /// as `[ "ns", "name" ]` or `[ "outer", "inner", "name" ]`. An array containing a single
    /// string, such as `[ "name" ]`, is not namespaced and is the same name as `"name"`.
    /// 
    /// Each of the following encodes into a distinct value:
    /// 
    ///   `"name"` or `[ "name" ]`
    ///   `[ "a", "name" ]`
    ///   `[ "b", "name" ]`
    ///   `[ "a", "a", "name" ]`
    ///   `[ "a", "b", "name" ]`
    ///   `[ "b", "b", "name" ]`
    ///   *etc.*
    /// 
    /// @name module:vwf~namespaceEncodedName
    /// 
    /// @param {String|String[]} memberName
    ///   A string, or an array of strings containing a name preceded by any number of namespace
    ///   names. In an array, each element defines a unique space for the member name and for
    ///   any intermediate namespaces.
    /// 
    /// @returns {String}

    namespaceEncodedName(memberName) {

        if (typeof memberName === "object" && memberName instanceof Array) {
            return (memberName.length !== 1) ? "vwf$" + memberName.join("$") : memberName[0];
        } else {
            return memberName;
        }

    }

    /// Convert a (potentially-abbreviated) component specification to a descriptor parsable by
    /// vwf.createChild. The following forms are accepted:
    /// 
    ///   - Descriptor: { extends: component, source: ..., type: ..., ... }
    ///   - Component URI: http://host/path/to/component.vwf
    ///   - Asset URI: http://host/ath/to/asset.type
    ///   - Node ID
    /// 
    /// They are converted as follows:
    /// 
    ///   - Descriptor: unchanged [1]
    ///   - Component URI: a component that extends the component identified by the URI
    ///   - Asset URI: a component having the asset identified by the URI as its source
    ///   - Node ID: a component that extends the previously-created node identified by the ID
    /// 
    /// [1] As a special case, missing MIME types are filled in for assets matcching the
    /// patterns *.unity3d and *.dae, and components having assets of those types but no
    /// prototype declared will be upgraded to extend scene.vwf and navscene.vwf, respectively.
    /// 
    /// @name module:vwf~normalizedComponent
    /// 
    /// @param {String|Object} component
    /// 
    /// @returns {Object}

    normalizedComponent(component) {

        // Convert a component URI to an instance of that type or an asset reference to an
        // untyped reference to that asset. Convert a component ID to an instance of that
        // prototype.

        if (this.componentIsURI(component)) {
            if (component.match(/\.vwf$/)) { // TODO: detect component from mime-type instead of extension?
                component = {
                    extends: component
                };
            } else {
                component = {
                    source: component
                };
            }
        } else if (this.componentIsID(component)) {
            component = {
                extends: component
            };
        }

        // Fill in the mime type from the source specification if not provided.

        if (component.source && !component.type) { // TODO: validate component

            var match = component.source.match(/\.([^.]*)$/); // TODO: get type from mime-type (from server if remote, from os if local, or (?) from this internal table otherwise)

            if (match) {

                switch (match[1]) {
                    case "unity3d":
                        component.type = "application/vnd.unity";
                        break;
                    case "dae":
                        component.type = "model/vnd.collada+xml";
                        break;
                }

            }

        }

        // Fill in the component type from the mime type if not provided.

        if (component.type && !component.extends) { // TODO: load from a server configuration file

            switch (component.type) {
                case "application/vnd.unity":
                    component.extends = "http://vwf.example.com/scene.vwf";
                    break;
                case "model/vnd.collada+xml":
                    component.extends = "http://vwf.example.com/navscene.vwf";
                    break;
            }

        }

        return component;
    }

    /// Convert a `Handler` specification into the standard form of an object containing
    /// `parameters`, `body` and `type` fields.
    /// 
    /// @name module:vwf~normalizedHandler
    /// 
    /// @param {Handler|string}
    /// @param {string[]} [defaultParameters]
    /// 
    /// @returns {Handler}

    normalizedHandler(handler, defaultParameters) {

        // Convert abbreviated forms to the explict `Handler` form.

        if (typeof handler !== "object" || handler instanceof Array) {
            handler = {
                body: handler
            }; //if (require("vwf/configuration").active["preserve-script-closures"]
        } else if (this.configuration["preserve-script-closures"] && (typeof handler == "function" || handler instanceof Function)) {
            handler = {
                body: handler
            };
        }

        // Use a default parameter list if the handler doesn't provide its own and if defaults
        // were provided.

        if (!handler.parameters && defaultParameters) {
            handler.parameters = defaultParameters;
        }

        // Fill in a default media type if `type` is not provided. A `body` of type `string` is
        // taken to be `application/javascript`.

        if (handler.type === undefined) {
            if (typeof handler.body === "string" || handler.body instanceof String) {
                handler.type = "application/javascript";
            }
        }

        return handler;
    }

    /// Convert a `fields` object as passed between the client and reflector and stored in the
    /// message queue into a form suitable for writing to a log.
    /// 
    /// @name module:vwf~loggableFields
    /// 
    /// @param {Object} fields
    /// 
    /// @returns {Object}

    loggableFields(fields) {
        return this.utility.transform(fields, this.utility.transforms.transit);
    }

    /// Convert a component URI, descriptor or ID into a form suitable for writing to a log.
    /// 
    /// @name module:vwf~loggableComponent
    /// 
    /// @param {String|Object} component
    /// 
    /// @returns {String|Object}

    loggableComponent(component) {
        return this.utility.transform(component, this.loggableComponentTransformation);
    }

    /// Convert an arbitrary JavaScript value into a form suitable for writing to a log.
    /// 
    /// @name module:vwf~loggableValue
    /// 
    /// @param {Object} value
    /// 
    /// @returns {Object}

    loggableValue(value) {
        let self = this;
        return this.utility.transform(value, function (object, names, depth) {
            object = self.utility.transforms.transit(object, names, depth);
            return typeof object == "number" ? Number(object.toPrecision(5)) : object; // reduce numeric precision to remove visual noise
        });
    }

    /// Convert an array of arbitrary JavaScript values into a form suitable for writing to a
    /// log.
    /// 
    /// @name module:vwf~loggableValues
    /// 
    /// @param {Object[]|undefined} values
    /// 
    /// @returns {Object[]|undefined}

    loggableValues(values) {
        return this.loggableValue(values);
    }

    /// Convert an object indexing arrays of arbitrary JavaScript values into a form suitable
    /// for writing to a log.
    /// 
    /// @name module:vwf~loggableIndexedValues
    /// 
    /// @param {Object|undefined} values
    /// 
    /// @returns {Object|undefined}

    loggableIndexedValues(values) {
        return this.loggableValue(values);
    }

    /// Convert script text into a form suitable for writing to a log.
    /// 
    /// @name module:vwf~loggableScript
    /// 
    /// @param {String|undefined} script
    /// 
    /// @returns {String}

    loggableScript(script) {
        return (script || "").replace(/\s+/g, " ").substring(0, 100);
    }

    // -- remappedURI --------------------------------------------------------------------------

    /// Remap a component URI to its location in a local cache.
    /// 
    /// http://vwf.example.com/component.vwf => http://localhost/proxy/vwf.example.com/component.vwf
    /// 
    /// @name module:vwf~remappedURI

    remappedURI(uri, baseURI) {

        // var match = uri.match( RegExp( "http://(vwf.example.com)/(.*)" ) );

        // if ( match ) {
        //     uri = window.location.protocol + "//" + window.location.host +
        //         "/proxy/" + match[1] + "/" + match[2];
        // }
        if (baseURI && uri[0] !== "/") {

            let newURI = "";
            let parts = baseURI.split('/');
            parts[parts.length - 1] = uri;
            parts.map(el => {
                newURI = newURI + el + '/';
            })

            return newURI.slice(0, -1)

        }
        return uri

    }

    // -- resolvedDescriptor -------------------------------------------------------------------

    /// Resolve relative URIs in a component descriptor.
    /// 
    /// @name module:vwf~resolvedDescriptor

    resolvedDescriptor(component, baseURI) {

        let selfKernel = this; 
        return this.utility.transform(component, resolvedDescriptorTransformationWithBaseURI);

        function resolvedDescriptorTransformationWithBaseURI(object, names, depth) {
            return selfKernel.resolvedDescriptorTransformation.call(selfKernel, object, names, depth, baseURI);
        }

    }

    // -- loggableComponentTransformation ------------------------------------------------------

    /// vwf/utility/transform() transformation function to truncate the verbose bits of a
    /// component so that it may be written to a log.
    /// 
    /// @name module:vwf~loggableComponentTransformation

    loggableComponentTransformation(object, names, depth) {

        // Get our bearings at the current recusion level.

        var markers = this.descriptorMarkers(object, names, depth);

        // Transform the object here.

        switch (markers.containerName) {

            case "extends":

                // Omit a component descriptor for the prototype.

                if (markers.memberIndex == 0 && this.componentIsDescriptor(object)) {
                    return {};
                }

                break;

            case "implements":

                // Omit component descriptors for the behaviors.

                if (markers.memberIndex == 0 && this.componentIsDescriptor(object)) {
                    return {};
                }

                break;

            case "properties":

                // Convert property values to a loggable version, and omit getter and setter
                // text.

                if (markers.memberIndex == 0 && !this.valueHasAccessors(object) ||
                    markers.memberIndex == 1 && names[0] == "value") {
                    return this.loggableValue(object);
                } else if (markers.memberIndex == 1 && (names[0] == "get" || names[0] == "set")) {
                    return "...";
                }

                break;

            case "methods":

                // Omit method body text.

                if (markers.memberIndex == 0 && !this.valueHasBody(object) ||
                    markers.memberIndex == 1 && names[0] == "body") {
                    return "...";
                }

                break;

            case "events":

                // Nothing for events.

                break;

            case "children":

                // Omit child component descriptors.

                if (markers.memberIndex == 0 && this.componentIsDescriptor(object)) {
                    return {};
                }

                break;

            case "scripts":

                // Shorten script text.

                if (markers.memberIndex == 0 && !this.valueHasType(object) ||
                    markers.memberIndex == 1 && names[0] == "text") {
                    return "...";
                }

                break;

        }

        return object;
    }

    // -- resolvedDescriptorTransformation -----------------------------------------------------

    /// vwf/utility/transform() transformation function to resolve relative URIs in a component
    /// descriptor.
    /// 
    /// @name module:vwf~resolvedDescriptorTransformation

    resolvedDescriptorTransformation(object, names, depth, baseURI) {

        // Get our bearings at the current recusion level.

        var markers = this.descriptorMarkers(object, names, depth);

        // Resolve all the URIs.

        switch (markers.containerName) {

            case "extends":
            case "implements":
            case "source":
            case "children":

                if (markers.memberIndex == 0 && this.componentIsURI(object)) {
                    return object //require( "vwf/utility" ).resolveURI( object, baseURI );
                }

                break;

            case "scripts":

                if (markers.memberIndex == 1 && names[0] == "source") {
                    return object //require( "vwf/utility" ).resolveURI( object, baseURI );
                }

                break;

        }

        return object;
    }

    // -- descriptorMarkers --------------------------------------------------------------------

    /// Locate the closest container (`properties`, `methods`, `events`, `children`) and
    /// contained member in a `vwf/utility/transform` iterator call on a component descriptor.
    /// 
    /// @name module:vwf~descriptorMarkers

    descriptorMarkers(object, names, depth) {

        // Find the index of the lowest nested component in the names list.

        var componentIndex = names.length;

        while (componentIndex > 2 && names[componentIndex - 1] == "children") {
            componentIndex -= 2;
        }

        // depth                                                  names  notes
        // -----                                                  -----  -----
        // 0:                                                        []  the component
        // 1:                                          [ "properties" ]  its properties object
        // 2:                          [ "propertyName", "properties" ]  one property
        // 1:                                            [ "children" ]  the children object
        // 2:                               [ "childName", "children" ]  one child
        // 3:                 [ "properties", "childName", "children" ]  the child's properties
        // 4: [ "propertyName", "properties", "childName", "children" ]  one child property

        if (componentIndex > 0) {

            // Locate the container ("properties", "methods", "events", etc.) below the
            // component in the names list.

            var containerIndex = componentIndex - 1;
            var containerName = names[containerIndex];

            // Locate the member as appropriate for the container.

            if (containerName == "extends") {

                var memberIndex = containerIndex;
                var memberName = names[memberIndex];

            } else if (containerName == "implements") {

                if (containerIndex > 0) {
                    if (typeof names[containerIndex - 1] == "number") {
                        var memberIndex = containerIndex - 1;
                        var memberName = names[memberIndex];
                    } else {
                        var memberIndex = containerIndex;
                        var memberName = undefined;
                    }
                } else if (typeof object != "object" || !(object instanceof Array)) {
                    var memberIndex = containerIndex;
                    var memberName = undefined;
                }

            } else if (containerName == "source" || containerName == "type") {

                var memberIndex = containerIndex;
                var memberName = names[memberIndex];

            } else if (containerName == "properties" || containerName == "methods" || containerName == "events" ||
                containerName == "children") {

                if (containerIndex > 0) {
                    var memberIndex = containerIndex - 1;
                    var memberName = names[memberIndex];
                }

            } else if (containerName == "scripts") {

                if (containerIndex > 0) {
                    if (typeof names[containerIndex - 1] == "number") {
                        var memberIndex = containerIndex - 1;
                        var memberName = names[memberIndex];
                    } else {
                        var memberIndex = containerIndex;
                        var memberName = undefined;
                    }
                } else if (typeof object != "object" || !(object instanceof Array)) {
                    var memberIndex = containerIndex;
                    var memberName = undefined;
                }

            } else {

                containerIndex = undefined;
                containerName = undefined;

            }

        }

        return {
            containerIndex: containerIndex,
            containerName: containerName,
            memberIndex: memberIndex,
            memberName: memberName,
        };

    }

    /// Locate nodes matching a search pattern. {@link module:vwf/api/kernel.find} describes the
    /// supported patterns.
    /// 
    /// This is the internal implementation used by {@link module:vwf.find} and
    /// {@link module:vwf.test}.
    /// 
    /// This function must run as a method of the kernel. Invoke it as:
    ///   `find.call( kernel, nodeID, matchPattern, initializedOnly )`.
    /// 
    /// @name module:vwf~find
    /// 
    /// @param {ID} nodeID
    ///   The reference node. Relative patterns are resolved with respect to this node. `nodeID`
    ///   is ignored for absolute patterns.
    /// @param {String} matchPattern
    ///   The search pattern.
    /// @param {Boolean} [initializedOnly]
    ///   Interpret nodes that haven't completed initialization as though they don't have
    ///   ancestors. Drivers that manage application code should set `initializedOnly` since
    ///   applications should never have access to uninitialized parts of the application graph.
    /// 
    /// @returns {ID[]|undefined}
    ///   An array of the node ids of the result.

    find(nodeID, matchPattern, initializedOnly) {

        // Evaluate the expression using the provided node as the reference. Take the root node
        // to be the root of the reference node's tree. If a reference node is not provided, use
        // the application as the root.

        var rootID = nodeID ? this.root(nodeID, initializedOnly) :
            this.application(initializedOnly);

        return this.xpath.resolve(matchPattern, rootID, nodeID,
            resolverWithInitializedOnly, this);


        // Wrap `xpathResolver` to pass `initializedOnly` through.

        function resolverWithInitializedOnly(step, contextID, resolveAttributes) {
            return this.xpathResolver.call(this, step, contextID, resolveAttributes, initializedOnly);
        }

    }

    // -- xpathResolver ------------------------------------------------------------------------

    /// Interpret the steps of an XPath expression being resolved. Use with
    /// vwf.utility.xpath#resolve.
    ///
    /// @name module:vwf~xpathResolver
    /// 
    /// @param {Object} step
    /// @param {ID} contextID
    /// @param {Boolean} [resolveAttributes]
    /// @param {Boolean} [initializedOnly]
    ///   Interpret nodes that haven't completed initialization as though they don't have
    ///   ancestors. Drivers that manage application code should set `initializedOnly` since
    ///   applications should never have access to uninitialized parts of the application graph.
    /// 
    /// @returns {ID[]}

    xpathResolver(step, contextID, resolveAttributes, initializedOnly) {
        let self = this;

        var resultIDs = [];

        switch (step.axis) {

            // case "preceding":  // TODO
            // case "preceding-sibling":  // TODO

            case "ancestor-or-self":
                resultIDs.push(contextID);
                Array.prototype.push.apply(resultIDs, this.ancestors(contextID, initializedOnly));
                break;

            case "ancestor":
                Array.prototype.push.apply(resultIDs, this.ancestors(contextID, initializedOnly));
                break;

            case "parent":
                var parentID = this.parent(contextID, initializedOnly);
                parentID && resultIDs.push(parentID);
                break;

            case "self":
                resultIDs.push(contextID);
                break;

            case "child":
                Array.prototype.push.apply(resultIDs,
                    this.children(contextID, initializedOnly).filter(function (childID) {
                        return childID;
                    }, this)
                );
                break;

            case "descendant":
                Array.prototype.push.apply(resultIDs,
                    this.descendants(contextID, initializedOnly).filter(function (descendantID) {
                        return descendantID;
                    }, this)
                );
                break;

            case "descendant-or-self":
                resultIDs.push(contextID);
                Array.prototype.push.apply(resultIDs,
                    this.descendants(contextID, initializedOnly).filter(function (descendantID) {
                        return descendantID;
                    }, this)
                );
                break;

            // case "following-sibling":  // TODO
            // case "following":  // TODO

            case "attribute":
                if (resolveAttributes) {
                    resultIDs.push("@" + contextID); // TODO: @?
                }
                break;

            // n/a: case "namespace":
            // n/a:   break;

        }

        switch (step.kind) {

            // Name test.

            case undefined:

                resultIDs = resultIDs.filter(function (resultID) {
                    if (resultID[0] != "@") { // TODO: @?
                        return self.xpathNodeMatchesStep.call(this, resultID, step.name);
                    } else {
                        return self.xpathPropertyMatchesStep.call(this, resultID.slice(1), step.name); // TODO: @?
                    }
                }, this);

                break;

            // Element test.

            case "element":

                // Cases: kind(node,type)

                // element()
                // element(name)
                // element(,type)
                // element(name,type)

                resultIDs = resultIDs.filter(function (resultID) {
                    return resultID[0] != "@" && self.xpathNodeMatchesStep.call(this, resultID, step.name, step.type); // TODO: @?
                }, this);

                break;

            // Attribute test.

            case "attribute":

                resultIDs = resultIDs.filter(function (resultID) {
                    return resultID[0] == "@" && self.xpathPropertyMatchesStep.call(this, resultID.slice(1), step.name); // TODO: @?
                }, this);

                break;

            // The `doc()` function for referencing globals outside the current tree.
            // http://www.w3.org/TR/xpath-functions/#func-doc.

            case "doc":

                if (this.root(contextID, initializedOnly)) {
                    var globalID = this.global(step.name, initializedOnly);
                    resultIDs = globalID ? [globalID] : [];
                } else {
                    resultIDs = [];
                }

                break;

            // Any-kind test.

            case "node":

                break;

            // Unimplemented test.

            default:

                resultIDs = [];

                break;

        }

        return resultIDs;
    }

    // -- xpathNodeMatchesStep -----------------------------------------------------------------

    /// Determine if a node matches a step of an XPath expression being resolved.
    ///
    /// @name module:vwf~xpathNodeMatchesStep
    /// 
    /// @param {ID} nodeID
    /// @param {String} [name]
    /// @param {String} [type]
    /// 
    /// @returns {Boolean}

    xpathNodeMatchesStep(nodeID, name, type) {

        if (name && this.name(nodeID) != name) {
            return false;
        }

        var matches_type = !type || this.uri(nodeID) == type ||
            this.prototypes(nodeID, true).some(function (prototypeID) {
                return this.uri(prototypeID) == type;
            }, this);

        return matches_type;
    }

    // -- xpathPropertyMatchesStep -------------------------------------------------------------

    /// Determine if a property matches a step of an XPath expression being resolved.
    ///
    /// @name module:vwf~xpathPropertyMatchesStep
    /// 
    /// @param {ID} nodeID
    /// @param {String} [name]
    /// 
    /// @returns {Boolean}

    xpathPropertyMatchesStep(nodeID, name) {

        var properties = this.models.object.properties(nodeID);

        if (name) {
            return properties[name];
        } else {
            return Object.keys(properties).some(function (propertyName) {
                return properties[propertyName];
            }, this);
        }

    }

    /// Merge two component descriptors into a single descriptor for a combined component. A
    /// component created from the combined descriptor will behave in the same way as a
    /// component created from `nodeDescriptor` that extends a component created from
    /// `prototypeDescriptor`.
    ///
    /// Warning: this implementation modifies `prototypeDescriptor`.
    ///
    /// @name module:vwf~mergeDescriptors
    ///
    /// @param {Object} nodeDescriptor
    ///   A descriptor representing a node extending `prototypeDescriptor`.
    /// @param {Object} prototypeDescriptor
    ///   A descriptor representing a prototype for `nodeDescriptor`.

    // Limitations:
    // 
    //   - Doesn't merge children from the prototype with like-named children in the node.
    //   - Doesn't merge property setters and getters from the prototype when the node provides
    //     an initializing value.
    //   - Methods from the prototype descriptor are lost with no way to invoke them if the node
    //     overrides them.
    //   - Scripts from both the prototype and the node are retained, but if both define an
    //     `initialize` function, the node's `initialize` will overwrite `initialize` in
    //     the prototype.
    //   - The prototype doesn't carry its location with it, so relative paths will load with
    //     respect to the location of the node.

    mergeDescriptors(nodeDescriptor, prototypeDescriptor) {

        if (nodeDescriptor.implements) {
            prototypeDescriptor.implements = (prototypeDescriptor.implements || []).
                concat(nodeDescriptor.implements);
        }

        if (nodeDescriptor.source) {
            prototypeDescriptor.source = nodeDescriptor.source;
            prototypeDescriptor.type = nodeDescriptor.type;
        }

        if (nodeDescriptor.properties) {

            prototypeDescriptor.properties = prototypeDescriptor.properties || {};

            for (var propertyName in nodeDescriptor.properties) {
                prototypeDescriptor.properties[propertyName] = nodeDescriptor.properties[propertyName];
            }

        }

        if (nodeDescriptor.methods) {

            prototypeDescriptor.methods = prototypeDescriptor.methods || {};

            for (var methodName in nodeDescriptor.methods) {
                prototypeDescriptor.methods[methodName] = nodeDescriptor.methods[methodName];
            }

        }

        if (nodeDescriptor.events) {

            prototypeDescriptor.events = prototypeDescriptor.events || {};

            for (var eventName in nodeDescriptor.events) {
                prototypeDescriptor.events[eventName] = nodeDescriptor.events[eventName];
            }

        }

        if (nodeDescriptor.children) {

            prototypeDescriptor.children = prototypeDescriptor.children || {};

            for (var childName in nodeDescriptor.children) {
                prototypeDescriptor.children[childName] = nodeDescriptor.children[childName];
            }

        }

        if (nodeDescriptor.scripts) {
            prototypeDescriptor.scripts = (prototypeDescriptor.scripts || []).
                concat(nodeDescriptor.scripts);
        }

        return prototypeDescriptor;
    }

    /// Return an {@link external:Object.defineProperty} descriptor for a property that is to be
    /// enumerable, but not writable or configurable. 
    /// 
    /// @param value
    ///   A value to wrap in a descriptor.
    /// 
    /// @returns
    ///   An {@link external:Object.defineProperty} descriptor.

    enumerable(value) {
        return {
            value: value,
            enumerable: true,
            writable: false,
            configurable: false,
        };
    }

    /// Return an {@link external:Object.defineProperty} descriptor for a property that is to be
    /// enumerable and writable, but not configurable. 
    /// 
    /// @param value
    ///   A value to wrap in a descriptor.
    /// 
    /// @returns
    ///   An {@link external:Object.defineProperty} descriptor.

    writable(value) {
        return {
            value: value,
            enumerable: true,
            writable: true,
            configurable: false,
        };
    }

    /// Return an {@link external:Object.defineProperty} descriptor for a property that is to be
    /// enumerable, writable, and configurable. 
    /// 
    /// @param value
    ///   A value to wrap in a descriptor.
    /// 
    /// @returns
    ///   An {@link external:Object.defineProperty} descriptor.

    configurable(value) {
        return {
            value: value,
            enumerable: true,
            writable: true,
            configurable: true,
        };
    }


    async chooseConnection(data) {
        if (this.isLuminary) {
            return await this.luminary.connect(data) //use Luminary
        } else {
            return data //use Reflector
        }
    }


}

export {
    VWF
}