1. A high-level programming language used in artificial intelligence research and applications, particularly expert systems. PROLOG, short for PROgramming in LOGic, is a declarative language; rather than tell the computer what procedure to follow to solve a problem, the programmer describes the problem to be solved. The language resembles the query language of a database management system such as Standard Query Language (SQL) in that you can use PROLOG to ask a question such as, "Is Foster City in Californian's But an important difference exists between PROLOG and a database management system (DBMS). A database contains information you can retrieve; a PROLOG program, in contrast, contains knowledge, from which the program can draw inferences about what is true or false. From QUECID

2. SWI-Prolog 5.0.0 From whatis