Offers a comprehensive free Prolog environment

SWI-Prolog
Free
Offline
http://www.swi-prolog.org/

SWI-Prolog offers a comprehensive free Prolog environment. Since its start in 1987, SWI-Prolog development has been driven by the needs of real world applications. SWI-Prolog is widely used in research and education as well as commercial applications. Join over a million users who have downloaded SWI-Prolog.