XML DTD or Schema for input

["David R. Patterson" <patterd1 comcast net>]

Is there a DTD or Schema for the input xml file for dia?  I'm trying to 
create a diagram via a program and have some questions about the UML 
Class diagram and related objects.

For example, there is a visibility attribute that has a "dia:enum" 
associated with it.  What are the values
of this enum field and what do they mean?

David Patterson
patterd1 at comcast dot net