XmlImplementation implements the DOMImplementation interface specification. The DOMImplementation is used as a place to keep certain methods that have no other logical home. Because the DOM is specified using IDL, there is no way to specify a constructor. Instead, you are expected to create a new DOM Document by calling DOMImplementation.createDocument( ). In .NET, you can do this by either calling XmlImplementation.CreateDocument( ) or by using the XmlDocument constructor.

DOMImplementation also requires a createDocumentType( ) method, which returns a DocumentType node. The DocumentType represents the contents of a DTD. .NET adds the method CreateDocumentType( ) to the XmlDocument class instead.

Finally, DOMImplementation requires the hasFeature( ) method. This method, which I used in Example 5-1, can be used to determine what features of the DOM are available for use in a given implementation.