/**
                                 * The State class maintains state for a collection of named items, with
                                 * a varying number of properties defined.
                                 *
                                 * It avoids the need to create a separate class for the item, and separate instances
                                 * of these classes for each item, by storing the state in a 2 level hash table,
                                 * improving performance when the number of items is likely to be large.
                                 *
                                 * @constructor
                                 * @class State
                                 */
                                Y.State = function() {
                                    /**
                                     * Hash of attributes
                                     * @property data
                                     */
                                    this.data = {};
                                };
                            
                                Y.State.prototype = {
                            
                                    /**
                                     * Adds a property to an item.
                                     *
                                     * @method add
                                     * @param name {String} The name of the item.
                                     * @param key {String} The name of the property.
                                     * @param val {Any} The value of the property.
                                     */
                                    add: function(name, key, val) {
                                        var item = this.data[name];
                            
                                        if (!item) {
                                            item = this.data[name] = {};
                                        }
                            
                                        item[key] = val;
                                    },
                            
                                    /**
                                     * Adds multiple properties to an item.
                                     *
                                     * @method addAll
                                     * @param name {String} The name of the item.
                                     * @param obj {Object} A hash of property/value pairs.
                                     */
                                    addAll: function(name, obj) {
                                        var item = this.data[name],
                                            key;
                            
                                        if (!item) {
                                            item = this.data[name] = {};
                                        }
                            
                                        for (key in obj) {
                                            if (obj.hasOwnProperty(key)) {
                                                item[key] = obj[key];
                                            }
                                        }
                                    },
                            
                                    /**
                                     * Removes a property from an item.
                                     *
                                     * @method remove
                                     * @param name {String} The name of the item.
                                     * @param key {String} The property to remove.
                                     */
                                    remove: function(name, key) {
                                        var item = this.data[name];
                            
                                        if (item) {
                                            delete item[key];
                                        }
                                    },
                            
                                    /**
                                     * Removes multiple properties from an item, or removes the item completely.
                                     *
                                     * @method removeAll
                                     * @param name {String} The name of the item.
                                     * @param obj {Object|Array} Collection of properties to delete. If not provided, the entire item is removed.
                                     */
                                    removeAll: function(name, obj) {
                                        var data;
                            
                                        if (!obj) {
                                            data = this.data;
                            
                                            if (name in data) {
                                                delete data[name];
                                            }
                                        } else {
                                            Y.each(obj, function(value, key) {
                                                this.remove(name, typeof key === 'string' ? key : value);
                                            }, this);
                                        }
                                    },
                            
                                    /**
                                     * For a given item, returns the value of the property requested, or undefined if not found.
                                     *
                                     * @method get
                                     * @param name {String} The name of the item
                                     * @param key {String} Optional. The property value to retrieve.
                                     * @return {Any} The value of the supplied property.
                                     */
                                    get: function(name, key) {
                                        var item = this.data[name];
                            
                                        if (item) {
                                            return item[key];
                                        }
                                    },
                            
                                    /**
                                     * For the given item, returns an object with all of the
                                     * item's property/value pairs. By default the object returned
                                     * is a shallow copy of the stored data, but passing in true
                                     * as the second parameter will return a reference to the stored
                                     * data.
                                     *
                                     * @method getAll
                                     * @param name {String} The name of the item
                                     * @param reference {boolean} true, if you want a reference to the stored
                                     * object
                                     * @return {Object} An object with property/value pairs for the item.
                                     */
                                    getAll : function(name, reference) {
                                        var item = this.data[name],
                                            key, obj;
                            
                                        if (reference) {
                                            obj = item;
                                        } else if (item) {
                                            obj = {};
                            
                                            for (key in item) {
                                                if (item.hasOwnProperty(key)) {
                                                    obj[key] = item[key];
                                                }
                                            }
                                        }
                            
                                        return obj;
                                    }
                                };