// Code from a demo at apple.com on October 3, 2007
// http://developer.apple.com/internet/webcontent/XMLHttpRequestExample/example.html

// retrieve XML document (reusable generic function);
// parameter is URL string (relative or complete) to
// an .xml file whose Content-Type is a valid XML
// type, such as text/xml; XML source must be from
// same domain as HTML file
function loadXMLDoc(url) {
	
	// branch for native XMLHttpRequest object
	if (window.XMLHttpRequest) {
		req = new XMLHttpRequest();
		req.onreadystatechange = processReqChange;
		req.open("GET", url, true);
		req.send(null);
		
	// branch for IE/Windows ActiveX version
	} else if (window.ActiveXObject) {
		isIE = true;
		req = new ActiveXObject("Microsoft.XMLHTTP");
		if (req) {
			req.onreadystatechange = processReqChange;
			req.open("GET", url, true);
			req.send();
		}
	}
}

// handle onreadystatechange event of req object
function processReqChange() {
	// only if req shows "loaded"
	if (req.readyState == 4) {
		// only if "OK"
		if (req.status == 200) {
			// This function is defined in another JavaScript file
			whenRequestReceived(req);
		} else {
			alert("There was a problem retrieving the XML data:\n" +
			req.statusText);
		}
	}
}