DOCBOOK-APPS: XML equivalent of (o)nsgmls?

Folks,

I'm starting to play a little bit with XML/XSL versus SGML/DSSSL and
one thing I can't seem to find yet is the answer to this:

 - with current XML tools, is there an equivalent to 'nsgmls' or
   'onsgmls' that will validate the XML code?

I use onsgmls all the time to validate the SGML code before I process
it into other formats.  Is there an equivalent type of thing I can do
with Xalan, Saxon or some other tool?

I work on Linux and would want a command-line option.

Thanks,
Dan

-- 
Dan York, Director of Training        
Ph: +1-613-751-4401  Mobile: +1-613-263-4312 Fax: +1-613-564-7739 
e-smith, inc. 150 Metcalfe St., Suite 1500, Ottawa,ON K2P 1P1 Canada
http://www.e-smith.com/            open source, open mind