[Core] Class diagram of the Core meta-model

All,

I tried to extract the meta-model that underlies the BNF in the current 
version of the Core spec [1]. I attach the class diagrams.

I have two difficulties with the diagram for the RIF Condition Language:
- I added an "Equation" class because I needed something to which the 
two terms in an equality literal would be attached;
- I do not know how to show that an Expr is either an Atom or a Term. 
Actually, I wonder if it even makes sense to have something like this in 
a meta-model. Anyway, what I did, in the diagram, is that I made Expr 
both a sub-class of Atom and Term; which is wrong, of course...

<Chair's hat off>
Notice that this email does not imply anything in terms of my personal 
endorsement of the diagrammed meta-model: I only tried to stay as close 
as possible to the BNF in [1] and the diagrams are only meant to provide 
a bottom-line to the discussion that we need to have wrt the Core 
meta-model.
</Chair's hat off>

[1] http://www.w3.org/2005/rules/wg/wiki/Core

Cheers,

Christian