Design

The design of JGUM was most heavily influenced by this article which provided excellent distinctions regarding groups, users, roles, permissions and resources:
http://www.javaworld.com/javaworld/jw-06-2001/jw-0615-tapestry_p.html

This picture explains a lot of the concepts:

The API consists for the core objects Group, User, Role, Permission and Resource. The system lets you set up any configuration of Groups, Users, and Roles. You then assign Permissions to these entities.

The main things the system does in relation to these objects is:

• lets you ask questions like - Can the current user access a resource (which might be the ability to click on a link)

Note this Tapestry is very different than the project by the same name hosted at Apache.