Preparing the syllabus for my graduate software engineering course, I stumbled on http://www.eclipse.org/modeling/ which leads eventually to the recently adopted OMG Ontology Definition Metamodel (ODM) http://www.omg.org/docs/ad/06-05-01.pdf
In Model Directed Architecture, a Metamodel constrains how you can model your problems. Metamodels are always implicitly or explicitly behind any modeling tools. Explicit is better, because then the tools can analyze your conformance to the model. The eclipse modeling framework (EMF) supports this, so that tools like the IBM Rational Software Modeling and Rational Software Architect eclipse packages can implement it. Probably so do other modeling tools.
In the detailed TOC of the above PDF, one will find every single topic around which the TAG discussions have swirled, and more.
I'm sure that everyone on this list shares my excitement in finding that there is potentially a rigorous framework for the tag ontology efforts and will drop everything else to absorb this 338 page specification before coming to St. Louis, at which the program should be revised to comprise nothing else but its discussion for the entire week. Hah, hah, just serious.
--Bob