Document and Element trick!Please give me hand

Question

hello there
I have a question for ya
What is the difference between Document and Element regarding XML
If I have this
Document r ; how I could convert it Element say e; and vice versa
it is possible to say
Document r;
Element e = (Element) r;
what about
Element e;
Document r = (Document) e;
Thank you alot

Answer 1

A document is, well the root [url http://www.w3.org/TR/2003/WD-DOM-Level-3-Core-20030226/core.html#ID-1950641247]node of the document tree. A element is a node in the document tree.
[url http://www.w3.org/TR/2003/WD-DOM-Level-3-Core-20030226/core.html#i-Document]Document
The Document interface represents the entire HTML or XML document. Conceptually, it is the root of the document tree, and provides the primary access to the document's data.
Since elements, text nodes, comments, processing instructions, etc. cannot exist outside the context of a Document, the Document interface also contains the factory methods needed to create these objects. The Node objects created have a ownerDocument attribute which associates them with the Document within whose context they were created.
[url http://www.w3.org/TR/2003/WD-DOM-Level-3-Core-20030226/core.html#ID-745549614]Element
The Element interface represents an element in an HTML or XML document. Elements may have attributes associated with them; since the Element interface inherits from Node, the generic Node interface attribute attributes may be used to retrieve the set of all attributes for an element. There are methods on the Element interface to retrieve either an Attr object by name or an attribute value by name. In XML, where an attribute value may contain entity references, an Attr object should be retrieved to examine the possibly fairly complex sub-tree representing the attribute value. On the other hand, in HTML, where all attributes have simple string values, methods to directly access an attribute value can safely be used as a convenience.
Recomended Reading:
http://www.w3.org/TR/2003/WD-DOM-Level-3-Core-20030226/core.html