XMLHttpRequest support in QML is patchy

The example here
http://doc.qt.nokia.com/4.7-snapshot/declarative-xml-xmlhttprequest-xmlhttprequest-example-qml.html
suggests that the JavaScript XMLHttpRequest is supported from within
a QML file, yet it seems the support is very limited (intentionally or not).
While some functions like XMLHttpRequest's getAllResponseHeaders() works,
the majority seem inaccessible (like getElementsByTagName() and the node's
getAttributeNode()). It would be very useful if the support were at least
a little more complete, so that attributes can be accessed.