PSGML for the future?

PSGML for the future?

[Arturius mac Aidan]

I see that people seem to be moving to RELAX NG in place of DTDs.  For now
they seem to be providing DTDs to go with the rnc schemas.  But the
implication is that these may not be 100% faithful to the definitive
document model expressed in RELAX NG.  I like PSGML, even though it has
some limitations.  One feature it provides over nXML is the ability to wrap
a region with a tag pair.  Another important feature of PSGML is that I
know how to use it (for the most part).  As far as I know PSGML only works
with DTDs.  Is that correct?

I have stuff like this in some of my documents and PSGML complains that
"attribute xmlns:xi not declared for element xi:include"

  <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="logic.xml"/>
  <xi:include xmlns:xi="http://www.w3.org/2001/XInclude"
href="glossary.xml"/> 

This is the whole document:

<?xml version="1.0"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.3b5//EN"
                 "/home/hattons/opt/org/docbook/xml-4.3b5/docbookx.dtd">
<book>
  <title>Foundational Concepts of Mathematics</title>
  <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="logic.xml"/>
  <xi:include xmlns:xi="http://www.w3.org/2001/XInclude"
href="glossary.xml"/> 
</book>

Can I expect PSGML to handle namespaces?  There was a time when I thought it
did, but it seems not to be working these days.
-- 
.