An XML model is a graphical representation of an XML Schema Definition file (.XSD), a
Document Type Definition file (.DTD) or an XML-Data Reduced file (.XDR).
With its Browser tree view and diagram, an XML model gives you a global and
schematic view of all the elements composing an XSD, a DTD or an XDR file.
This is very helpful when you need to understand, check or modify the complex 
structure of an XSD, a DTD or an XDR file.