Question about progressive loading

[chao]

Hi Nick,

    I am a new user of time map, and have some silly questions about progressive loading.

    OK, I want to load my data progressively and what does the  url used for?  Because I don't know anything about PHP. and the whole project is based on javascript. Is the data is store in that location? Could I store my data locally? 

    I read the source code of the example and source code of json.js. then I find something in json.js:

/**
 * @class
 * JSON string loader factory - expects a plain JSON array.
 *
 * <p>The json_string loader assumes an array of items in plain JSON, with no
 * callback function - this will require a local URL.</p>
 * <p>Note that this loader requires lib/json2.pack.js.</p>
 *
 * @augments TimeMap.loaders.remote
 *
 * @requires lib/json2.pack.js
 *
 * @example
TimeMap.init({
    datasets: [
        {
            title: "JSON String Dataset",
            type: "json_string",
            options: {
                url: "mydata.json"    // Must be a local URL
            }
        }
    ],
    // etc...
});
 *
 * @param {Object} options          All options for the loader
 * @param {String} options.url          URL of JSON file to load
 * @param {mixed} [options[...]]        Other options (see {@link TimeMap.loaders.remote})
 */
TimeMap.loaders.json_string = function(options) {
    var loader = new TimeMap.loaders.remote(options);
    
    /**
     * Parse a JSON string into a JavaScript object, using the json2.js library.
     * @name TimeMap.loaders.json_string#parse
     * @function
     * @param {String} json     JSON string to parse
     * @returns {Object}        Parsed JavaScript object
     */
    loader.parse = JSON.parse;
    
    return loader;
};

// Probably the default json loader should be json_string, not
// jsonp. I may change this in the future, so I'd encourage you to use
// the specific one you want.
TimeMap.loaders.json = TimeMap.loaders.jsonp;

======================================================

so can I write something like:

$(function() { 
 tm = TimeMap.init({ 
   mapId: "map",               // Id of map div element (required) 
   timelineId: "timeline",     // Id of timeline div element 

   datasets: [ 
   { 
     title: "Progressive Dataset", 

     type: "progressive", 
     options: { 
     // Data to be loaded in JSON locally

     items: items, 
     type: "json", 
     url: "mydata.json",

     start:"2012-07-29",

     dateMinDate:"2012-07-29",

     interval: 10368000000 //15days

  // function to turn date into string appropriate for service 
     formatDate: function(d) { 
     return TimeMap.util.formatDate(d, 1); 

   } 
 } 
} 
], 
bandIntervals: "hr" 
}); 
}); 

And I am not quite understand the [start] and [end] part, I look at one topic and his url is 

     url: "http://xxx.yyy.com/progaj.php? 
start=[start]&end=[end]&seq_id=225&callback=?",  does this means I need to write an PHP file to indicate the start time and end time?

As I mentioned above, I am almost new to javascript and php, is there a way that I can pas the data locally and progressively?

If yes, what's should be in for each item in that json file?

like:

{ 

    {  //first data
     "title" : "My Item1", 
     "start" : "2008-02-01",  
     "point" : { 
         "lat" : 43.6433, 
         "lon" : 11.9875 
     }, 
     "options" : {   
            "some data": "info" 

     },

    {  //first data
     "title" : "My Item2", 
     "start" : "2008-02-02",  
     "point" : { 
         "lat" : 41.6433, 
         "lon" : 10.9875 
     }, 
     "options" : {   
            "some data": "info" 

     }, 

   ... and so on

}

Thank you in advance.