Except we're talking about Prolog, so we're talking about SWI-Prolog, the insanely academic flavour of this programming language. It's basically the flavour of

Except we're talking about Prolog, so we're talking about SWI-Prolog, the insanely academic flavour of this programming language. It's basically the flavour of Prolog that won the popularity contest exactly because of its academic sponsorship (by the University of Amsterdam).