validating against a dtd with GSXMLParser?

[e.sammer]

all:

is it possible to validate an xml document against a dtd using 
GSXMLParser? i noticed the [-doValidityChecking:(BOOL)] method (i think 
that was it), but no matter what, it doesn't seem to check against the 
dtd. i'm not doing anything overly complex - just like:


parser = [GSXMLParser parserWithContentsOfFile:aFile];
[parser doValidityChecking:YES];

if ([parser parse] == NO) {
 ...
}

etc...

am i missing something?
thanks in advance.

--
eric.sammer
eric@lifeless.net