/**
                             * Extends DataSource with polling functionality.
                             *
                             * @module datasource
                             * @submodule datasource-polling
                             */
                            
                            /**
                             * Adds polling to the DataSource Utility.
                             * @class Pollable
                             * @extends DataSource.Local
                             */
                            function Pollable() {
                                this._intervals = {};
                            }
                            
                            Pollable.prototype = {
                            
                                /**
                                * @property _intervals
                                * @description Hash of polling interval IDs that have been enabled,
                                * stored here to be able to clear all intervals.
                                * @private
                                */
                                _intervals: null,
                            
                                /**
                                 * Sets up a polling mechanism to send requests at set intervals and
                                 * forward responses to given callback.
                                 *
                                 * @method setInterval
                                 * @param msec {Number} Length of interval in milliseconds.
                                 * @param [request] {Object} An object literal with the following properties:
                                 *     <dl>
                                 *     <dt><code>request</code></dt>
                                 *     <dd>The request to send to the live data source, if any.</dd>
                                 *     <dt><code>callback</code></dt>
                                 *     <dd>An object literal with the following properties:
                                 *         <dl>
                                 *         <dt><code>success</code></dt>
                                 *         <dd>The function to call when the data is ready.</dd>
                                 *         <dt><code>failure</code></dt>
                                 *         <dd>The function to call upon a response failure condition.</dd>
                                 *         <dt><code>argument</code></dt>
                                 *         <dd>Arbitrary data payload that will be passed back to the success and failure handlers.</dd>
                                 *         </dl>
                                 *     </dd>
                                 *     <dt><code>cfg</code></dt>
                                 *     <dd>Configuration object, if any.</dd>
                                 *     </dl>
                                 * @return {Number} Interval ID.
                                 */
                                setInterval: function(msec, request) {
                                    var x = Y.later(msec, this, this.sendRequest, [ request ], true);
                                    this._intervals[x.id] = x;
                                    // First call happens immediately, but async
                                    Y.later(0, this, this.sendRequest, [request]);
                                    return x.id;
                                },
                            
                                /**
                                 * Disables polling mechanism associated with the given interval ID.
                                 *
                                 * @method clearInterval
                                 * @param id {Number} Interval ID.
                                 */
                                clearInterval: function(id, key) {
                                    // In case of being called by clearAllIntervals()
                                    id = key || id;
                                    if(this._intervals[id]) {
                                        // Clear the interval
                                        this._intervals[id].cancel();
                                        // Clear from tracker
                                        delete this._intervals[id];
                                    }
                                },
                            
                                /**
                                 * Clears all intervals.
                                 *
                                 * @method clearAllIntervals
                                 */
                                clearAllIntervals: function() {
                                    Y.each(this._intervals, this.clearInterval, this);
                                }
                            };
                            
                            Y.augment(Y.DataSource.Local, Pollable);