As stated in the other thread (http://community.jboss.org/thread/155681?tstart=0), we plan of rearchitecting the internals of the STS to be the generic token generator.
Toward this, I created the first stab at an architecture diagram for the STS.
The DIA image source is available in the picketlink workspace: http://anonsvn.jboss.org/repos/picketlink/picketlink-docs/trunk/images/