It is the URI of the VOMS Server for your VO (attribute "UserVO"). If you have the gLite UI environment on your box, you can omit this
attribute. The URI will be found in the gLite "vomses" directory that you can set in the "Vomses" attribute.
If the "Vomses" attribute is not set, the URI will be found in "$HOME/.glite/vomses" or "$HOME/.voms/vomses" or "/etc/vomses".
You need to install the JCE (Java Cryptography Extension) Unlimited Strength
Jurisdiction Policy Files (JAR Files) into your JRE (in the lib/security directory).
You can download these files on the official Java website.