In [War83], Warren describes the WAM in a minimalist s style, making understanding very difficult for the average reader, even with a foreknowledge of Prolog s operations. Too much is left untold, and very little is justified in clear terms.(David H. D. Warren's confides privately that he felt [that the WAM] was important, but [its] details unlikely to be of wide interest. Hence, [he used a] personal notes style.) This has resulted in a very scant number of WAM aficionados who could boast understanding the details of its workings.
[War83] David H. D. Warren. An abstract Prolog instruction set. Technical Note 309, SRI International, Menlo Park, CA, October 1983.