what's the value of the document type declaration?

got into a discussion last night with someone discussing
docbook transformation (being the party animal that i am),
and the question arose as to the value of the document type
declaration at the top of the XML file.  you know:

 <!DOCTYPE book ... blah blah ...>

  while the declaration is, of course, useful for validation,
it doesn't technically play a part in the actual transformation.

  i pointed out the one value that it includes all of the extra
entities, so that you can use things like &aleph; and &oplus;,
and so on.

  but beyond the inclusion of the addition entities, is there
some other value for the declaration?  just curious.

rday

--

Robert P. J. Day
Eno River Technologies
Unix, Linux and Open Source training
Waterloo, Ontario

www.enoriver.com