> Why is this better than something based on autoconfiguration 'busses,'
> etc.?
> 
> If you do it based on busses, and decide to move things around, it's
> easy to do.  You also have to represent only one layer (wire? 8-) at a
> time, which seems right.
Yes, I think I've changed my mind on this issue now.  Given
that physical location is going to be a locator.

        -- Lennart