Hi!
I would love to see such a lexicon too! I was looking for it when I started out making automated position type detection for Backgammon Studio but couldn't find any so I had to rely on the position types that were mentioned in chapter heading in books and my own understanding of these position types.
I asked for some input on this in a local forum and I think I got 3 different answers from 3 different players on what a specific position should be labelled as so that didn't work out too well.
Perhaps Chris Bray is aware of such a lexicon or book which tries to present an extensive list of all commonly used categories for positions?
Adding new position types to my server isn't too hard as long as I have a good definition of how to detect the position.
For instance I could add a 'Bear in' position type which would be defined as: No contact and number of checkers in your homeboard is less than 15 (with no checkers off). Are you still in a 'Bear in' if you have taken checkers off but have checkers in your outfield? I guess you are (or you could call it a 'post bearoff hit' position).
Doing this manually does sound like an awful lot of work though!
The added bonus of having a database of matches is that you with a couple of keystrokes can say something like "Give me all the -0.100 errors I did last week":
Oops..
But I guess there are many ways to work with your own match data possibly as many as there are backgammon players... I for one would love to hear more about how the Backgammon Giants do it! (and automate it a few days later! hehe..)
Best regards,
TP