NS6/NS7+ xmlDocument and xmlHttp

[wac]

Do these objects exist in NS6 or NS7?
I was looking at various sites which talk about
xmlDocument.create() and xmlHttp.create()
(for example http://www.webfx.eae.net/dhtml/xmlextras/xmlextras.html
)
but it wasn't clear to me how much of this stuff is in the latest released browser. It wasn't clear if I had to write the implementation or they were just sharing how it was done.

Right now I'm using
document.implementation.createDocument("", "doc", null)
to create the XML document object in NS6, so I can load a server XML file, but NS has no mechanism to load from a string or write out a DOM (Serialize) to a 'server' file. Before I start hacking, I'm wondering if I'm looking in the wrong direction. Its hard to tell how old some of this stuff is or if the article is just talking about unreleased CVS code

[jkd]

var dynamicdoc= (new DOMParser()).parseFromString("<bla>some random xml</bla>", "text/xml");

var serializedDoc = (new XMLSerializer()).serializeToString(document);