using local catalog in platform independent way

Hi,

    I'm using Docbook finally with some success after lots and lots of 
work ;-)

My software which is Java based includes the docbook and docbook-xsl 
tarballs and I want to use the DTD locally so my Ant tasks can create 
HTML from docbook using the style task without requiring network access.

I have the following in my file:

<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.3CR1//EN"
  "../common/docbook-xml-4.3CR1/docbookx.dtd" [

So I've determined this will work under Unix, but I don't think it works 
on Windows-- can anyone recommend some approach that will work for both 
operating systems?

    Thanks, Jason