1972: The first Prolog interpreter
at the University of Marseille

Basically, Prolog is theorem prover à la Robinson, restricted to the Horn clause subset of first-order logic. Its programs are made up of implication rules:

conclusion0    if    condition1  and  condition2  and ...   conditionn.

Procedural interpretation:

to prove conclusion0,
prove condition1  then  prove condition2  then ...  prove conditionn.

To demonstrate a goal, the engine follows a linear proof strategy, with backtracking.

Description of the preliminary Prolog:

Manual of the final version:

"Most Prolog systems in the world owe their parentage to the original Marseille interpreter" (W.F. Clocksin & C.S. Mellish).


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