SPAM-version for review

This is the main version for review, it's intended as nearly finished as 
far as Chris and I go ... I have marked a few things that remain to do and 
there are some obvious things like missing references etc.

The main doubts are:
+ are the semantics any good?
+ does my treatment of B-nodes as graph names work - I think so, but Pat 
thought it was too hard; there were some subtleties that end up in the 
footnotes.

I am not at all adverse to Pat saying, "oh no I had better write the semantics"

(Also section 9.5 needs something doing to it, which isn't marked in-line. 
It basically starts up on another paper, and so needs to be trimmed down to 
size)

The zip file is of the latex sources, there's no need to look at it for 
simple review; but if you want to send an update please do ...

Jeremy