SWI-Prolog

SWI-Prolog is a free implementation of the Prolog logic programming language, widely used for teaching and for semantic web applications. Its main author is Jan Wielemaker, who began the work in 1987 at the University of Amsterdam; the SWI in the name abbreviates the Dutch Sociaal-Wetenschappelijke Informatica, the former name of his research group there. It runs on Unix, Linux, Windows and Macintosh systems and ships with a large library collection: constraint logic programming solvers (CHR, CLP(FD), CLP(B) and CLP(QR)), multithreading, unit testing, a web server, RDF and SGML parsing, a GUI toolkit called XPCE, a Java bridge named JPL and developer tools with a graphical debugger and profiler. Unlike many Prolog systems it does not use the Warren Abstract Machine; it executes code on an extended ZIP virtual machine with only a handful of instructions, which lets compiled and interpreted code interleave. Its Pengines system lets queries be distributed across servers and web pages.