IMHO: There is a definite need to switch over from SGML to XML.

Why to switch from SGML to XML:
===============================
	- the only free [OpenSource] SGML processors seems to be
      OpenSP/OpenJade/OSP (especially for Linux)
	- OpenSP/OpenJade/OSP are quite bogus and of poor quality
	- OpenSP/OpenJade/OSP have bad/no documentation
	- OpenSP/OpenJade/OSP seem not maintained anymore are at least
      at a very poor quality
	- SGML seems for many people harder to understand 
	- SGML problems are hard to tackle (e.g. catalog setup problems etc.)
	
Pro for XML/XSLT:
=================
	- XML/XSLT is mainstream now
	- much more people know/are able to use/handle XML/XSLT wrt. SGML
	- there are a lot of free [OpenSource] tools for processing
	  XML files (e.g. xsltproc, xalan, java, saxon)
	- there are a lot of IDE[-plugins], which support easy writing/
	  validation and troubleshooting of XML/stylesheet files (e.g.
	  xmlbuddy, oxygen, xmlspy, emacs, ...)
	- using Docbook XSL stylesheets to convert docbooks into e.g. manpages
	  or html is much easier than with SGML tool stuff

Howto convert docbook SGML files into docbook XML files:
========================================================
	$ sed -e 's/DocBook V3.1/DocBook V4.1/' arping.sgml >arping.tmp
	$ sgml2xml -c /etc/sgml/catalog -xlower -xno-nl-in-tag -xempty arping.tmp \
		> arping.xml

	# Of course, you need to check aka proof read the new file, since as
    # mentioned above, sgml tools are not very smart ...
	
Howto convert a manpage docbook file into a traditional man page:
=================================================================
	$ xsltproc file:///opt/docbook/xsl/1.67.2/manpages/docbook.xsl arping.xml

Howto convert a docbook file into an html file:
===============================================
	$ xsltproc file:///opt/docbook/xsl/1.67.2/xhtml/docbook.xsl arping.xml \
		> arping.html

Where are all the tools:
========================
Docbook XSL:	http://sourceforge.net/projects/docbook/
xsltproc:		ftp://ftp.gnome.org/pub/GNOME/sources/libxslt/ 
				   (but usually part of every Linux distribution)
xalan:			http://xml.apache.org/xalani-j/
java:			http://java.sun.com/j2se/1.5.0/download.jsp
oxygen:			http://www.oxygenxml.org/	
					(standalone and as eclipse-plugin)
					(commercial, but available for a reasonable price - 99$)
xmlbuddy:		http://xmlbuddy.com/
					(eclipse-plugin)
					(standard version is free; Pro 35$)

Can you show some examples for manpages:
========================================
- ../ps/psman.xml
- ../milter/milter-regex/milter-regex.dbk