Abstract Model contribution for module processing and also for attachments

[David, Stuart:  I would like to be added to the Abstract Model
subgroup.]

[Stuart:  The attachment here reflects some thinking that I have been
doing on an Abstract Model specification for Module Processing.  It also
contains some ideas on Attachments.  I would like to solicit general
discussion and offer them as starting points for inclusion in the
Abstract Model document.]

[Ray D., Ray W., Mahwan, Henrik:  For me to think clearly about how to
consider RPC, I needed to first attempt to clarify some kind of abstract
model for Module Processing first.  This is what you'll find in the
attachment.  It makes a small reference to RPC.  If you like the
framework, then maybe we can clarify what RPC is in this context.  It
seems like it is primarily a convention for how to interpret the markup
in a block and how to interpret the return result.]