Ti.XML.DOMImplementation and the use of...

I'm trying to create an XML documentin my app and then fire the XML off for processing.

I have the following snippet from my function

exports.xmlAddPaymentRecipient = function(prn, friendlyName, defaultAmount){
 
    var xmlDoc = Ti.XML.DOMImplementation.createDocument(null, "PaymentRecipient", Titanium.XML.DocumentType);
 
    var idElement = xmlDoc.createElement("name");
    var idText = xmlDoc.createTextNode("0");
    idElement.appendChild(idText);
    ....
    ....
}

'undefined' is not an object (evaluating 'Ti.XML.DOMImplementation.createDocument')

I've looked all over for examples of using Ti.XML.DOMImplementation but to no avail, any pointers as to whats going on and how I should be using Ti.XML.DOMImplementation. I don't want to use strings and concatenate them unless I absolutely have to.

Thanks