Yes - I have a printed copy of that, actually. It's not the end of Prolog evolution, but it's a good snapshot of common implementation techniques, and it definitely clarified things.

Here's a (rather snarky) LtU comment by Peter Van Roy pointing to other designs improving on the WAM - http://lambda-the-ultimate.org/classic/message1618.html#1108...

Easier link http://wambook.sf.net/