Accessing data from a server is easy with DataSource.IO, which uses the IO Utility to retrieve data over HTTP. A DataSchema plugin is used to normalize incoming data into a known format for consistency of usage by other components.
If your server returns JSON data, use a DataSourceJSONSchema plugin to parse the data against a schema that you provide:
YUI().use("datasource-io", "datasource-jsonschema", function(Y) {
    var myDataSource = new Y.DataSource.IO({source:"ysearch_json_madonna.php"}),
        myCallback = {
            success: function(e){
                alert(e.response);
            },
            failure: function(e){
                alert("Could not retrieve data: " + e.error.message);
            }
        };
    myDataSource.plug(Y.Plugin.DataSourceJSONSchema, {
        schema: {
            resultListLocator: "ResultSet.Result",
            resultFields: ["Title"]
        }
    });
    
    // This request string will get appended to the URI
    myDataSource.sendRequest({
        request:"?output=json",
        callback:myCallback
    });
});
On the other hand, a DataSourceXMLSchema plugin can be used to parse XML data coming from your server:
YUI().use("datasource-io", "datasource-xmlschema", function(Y) {
    var myDataSource = new Y.DataSource.IO({source:"ysearch_xml_madonna.php"}),
        myCallback = {
            success: function(e){
                alert(e.response);
            },
            failure: function(e){
                alert("Could not retrieve data: " + e.error.message);
            }
        };
    myDataSource.plug(Y.Plugin.DataSourceXMLSchema, {
        schema: {
            resultListLocator: "result",
            resultFields: [{key:"title", locator:"*[local-name() ='title']"}]
        }
    });
    myDataSource.sendRequest({
        request:"?output=xml",
        callback:myCallback
    });
});