The Document object represents the entire XML document and is the primary means of access to it; it represents the top node of the DOM tree. Since none of the other nodes can exist outside of a document, it also contains all the factory methods necessary to create them. Once created, these child Node objects will each have an ownerDocument attribute associating them with the parent document.

Microsoft's implementation includes all of the base DOM document methods as well as additional methods and properties that support XSL and XML transformations. The document is the only object that can be created, all other objects and interfaces being accessed or created from within it.

There are two models of the Document: the free-threaded model and the rental threading model. They both behave exactly the same but differ in that the rental-treaded versions offer better performance because the parser doesn't need to manage concurrent access among threads.

Using JavaScript the two different models can be created in the following way:

var xml_doc = new ActiveXObject("Microsoft.XMLDOM");

var xml_ftdoc = new ActiveXObject("Microsoft.FreeThreadedXMLDOM");

And with VBScript:

Set objXMLDoc = CreateObject("Microsoft.XMLDOM")

Set objFTXMLDoc = new ActiveXObject("Microsoft.FreeThreadedXMLDOM")

Note:
documents or nodes created by one method cannot be combined with those created by the other.

A Document is also a Node object, and so inherits various properties and methods from it. For details of the values returned by the nodeName, nodeType and nodeValue properties for a Document, see the Node object.

This is a read-only property that returns the last child node of a node. If there is none, it returns null.

Syntax: Node.lastChild

namespaceURI Property
This property is read-only and returns the URI (Universal Resource Indentifier) of the namespace.

Syntax: Node.namespaceURI