Ext.onReady(function(){

    // create the Data Store
    var ds = new Ext.data.Store({
        // load using HTTP
        proxy: new Ext.data.ScriptTagProxy({url: 'http://www.sofsis.cl/sheldon.xml'}),

        // the return will be XML, so lets set up a reader
        reader: new Ext.data.XmlReader({
               // records will have an "Item" tag
               record: 'Item',
               id: 'ASIN',
               totalRecords: '@total'
           }, [
               // set up the fields mapping into the xml doc
               // The first needs mapping, the others are very basic
               {name: 'Author', mapping: 'ItemAttributes > Author'}
           ])
    });

    var cm = new Ext.grid.ColumnModel([
	    {header: "Author", width: 120, dataIndex: 'Author'}
	]);
    cm.defaultSortable = true;

    // create the grid
    var grid = new Ext.grid.Grid('mygrid', {
        ds: ds,
        cm: cm
    });
    grid.render();

    ds.load();
});