Structure of Prolog Programs

Every entry into the interpreter is a goal that Prolog tries to satisfy.

Every goal in Prolog ends with ``.''.

A Prolog program consists of a database of facts, rules, and queries. This program is, in essence, a knowledge base.

• Fact: head but no body
  man(socrates).
  man(plato).
• Rules: head and body
  mortal(X) :- man(X).
• Questions: body but no head
  mortal(X).
  Use ``;'' to get next possible answer, Return to end.
  Yes means true with no variables, no means not consistent with database.