Hi
Check under your JBoss install directory:
YourInstallDir\jboss-3.0.0beta\lib\ext\jboss.jar\
& go into this archive for org\jboss\metadata\jaws_3_0.dtd
It's also available at http://www.jboss.org/j2ee/dtd, but it has the old version (beta instead of beta2)