I have xml files with the DTD spec:
<!DOCTYPE links SYSTEM "../Links.dtd">
That is, the dtd for all these files is
in their parent directory.

This is in a web application run by
Tomcat 4.0 (Catalina).  If I put the 
xerces.jar in webapps/myapp/WEB-INF/lib
it works fine.  However, Catalina currently
has a security bug that prevents me from
putting it there (xerces gets security
exceptions trying to access the files).

But, since this is a shared lib it makes
sense anyway to put it in common/lib.
However, when I put it there, it interprets
the relative DTD path as relative to 
whatever directory Catalina is run in!

This is unworkable from a web app developer's
point of view.  There might be multiple 
reasonable interpretations of a relative DTD
path, but from a developer's viewpoint there
are some essential elements:

1) It needs to be consistent regardless of 
where xerces.jar is loaded from
2) It cannot require the developer to specify
a relative path that makes any assumption 
about where Tomcat is installed or the name
of the web app main directory (since these
vary from install to install and are not
under developer control).

Craig R. McClanahan [craigmcc@apache.org]
from Tomcat says that this is a xerces bug,
not Tomcat.