Facts, Formulas, and Frames

The set of facts in an Algernon knowledge base can be viewed in two different ways.

• Viewed as a logic, the KB contains a collection of ground atomic formulas, representing predicates applied to constant symbols.
• Viewed as a semantic network, the KB contains a collection of frames describing individual objects, linked by known relations.

An advantage of the logic view is the vast body of relevant theory, useful for providing guarantees of expressive and inferential power. An advantage of the semantic network view is that the organization of knowledge into frames provides direct access to relevant information, and supports tractable reasoning. The (conceptual) objects related to a frame can be easily accessed by looking in a slot of the frame without searching the entire knowledge-base.

In Algernon, these two views are equivalent, since the ground atomic formula  r(f,g) is represented by placing the value g in the values facet of the r slot of the frame f [Hayes, 1979]. Similarly, if we know , the value h is placed in the non-values facet of the r slot of the frame f.