Validating against a XML schema in Debian?

[Stephane Bortzmeyer <bortzmeyer@nic.fr>]

What do you use to validate a XML file (in my case, a WSDL file)
against a schema, using only Debian packages in main?

With woody, I find no solution.

With sarge, I find no simple solution. I tried to use libxerces but,
until now, I fail (see later).

I installed libxml-xerces-perl and wrote a simple script (strongly
inspired from DOMPrint) to validate. But it keeps saying:

% perl xerces.pl -v=always -n -s WSDL/AmazonWebServices.wsdl
Error in eval: ERROR:
FILE:    /home/bortzmeyer/AFNIC/formation/web-services_long/WSDL/AmazonWebServices.wsdl
LINE:    6
COLUMN:  368
MESSAGE: Unknown element 'definitions'
 at xerces.pl line 62
 at xerces.pl line 63

while <definitions> is of course known by the schema and WSDL is the
default namespace. Running tcpdump, I do not even see an attempt to
retrieve the schema.