[Paraview] XML file name question

[Robert Ferrell]

I have a question about the file extension conventions for VTK XML files.

Each data type and file type is paired with a particular file extension. 
What is the purpose of having different file extensions?  The 'type'
attribute of the root element (VTKFile) uniquely identifies the type of
data contained in the root element.  So, the file extension information is
redundant.  Also, why is the 'type' attribute needed on the root element? 
The name of the first subordinate element must correspond the the 'type'.

As I see it, there are three distinct items of information which all must
match but all provide the same information:

 * file extension
 * type attribute of root element
 * name of the first subordinate element

Wouldn't everything be simpler if only the third item were used?  What
would not work?

This is not criticism.  I'm simply curious.

thanks,
-robert