AFAIK Watson doesn't generate Prolog. It does use Prolog rules:
"Specifically, decomposition for Puzzle questions is performed by matching manually developed Prolog rules against the question’s predicate-argument structure to identify its subparts.",
"Relation detection patterns are written in Prolog and apply unification pattern matching over PAS"
"Most of our rule-based question analysis components are implemented in Prolog"
(All from the IBM system journal issue on Watson).
I'm pretty sure I've read all the published papers on Watson (the QA system). It's possible I've missed something, so a citation would be great if I have.
The missing puzzle piece for your understanding, is how Prolog works. Prolog is declarative programming language, the program logic is expressed in terms of relations, represented as facts and rules. A computation is initiated by running a query over these relations.
"Specifically, decomposition for Puzzle questions is performed by matching manually developed Prolog rules against the question’s predicate-argument structure to identify its subparts.",
"Relation detection patterns are written in Prolog and apply unification pattern matching over PAS"
"Most of our rule-based question analysis components are implemented in Prolog"
(All from the IBM system journal issue on Watson).
I'm pretty sure I've read all the published papers on Watson (the QA system). It's possible I've missed something, so a citation would be great if I have.