Facts: Facts can be stored in a propositional database:
(DOG DOG1) (NAME DOG1 FIDO) (HOUND DOG1) (LOVES JOHN MARY)Facts can be retrieved in response to patterns:
(LOVES JOHN MARY) Does John love Mary? (LOVES JOHN ?X) Whom does John love? (LOVES ?X MARY) Who loves Mary? (LOVES ?X ?Y) All pairs of lovers.
Knowledge: Knowledge is stored as logical axioms that can be used for deduction. For example, the rule that `all hounds howl' could be represented as:
(ALL X (IF (HOUND X) (HOWL X)))or
(IF (HOUND ?X) (HOWL ?X))