next up previous contents
Next: Taxonomy Up: Example: FramesAccess Paths, Previous: Calling Algernon from Lisp

The Structure of an Algernon Theory

A theory in Algernon has a conventional format, which is not strictly required, but greatly simplifies creation and understanding of the program. It normally consists of the following five sections.

  1. Taxonomy: define a containment hierarchy of sets of objects that appear in the theory and certain individual elements of those sets.
  2. Slots: define the relations that may hold among those objects.
  3. Rules: define the forward- and backward-chaining inferences that can take place using those relations.
  4. Facts: assert the specific facts of the situation to be reasoned about. Forward-chaining rules invoked by the assertion of these facts, and backward-chaining rules invoked by the antecedents of those rules, may cause a significant amount of inference to take place.
  5. Queries: query the knowledge base for desired information. Backward-chaining rules invoked by the query, and forward-chaining rules invoked by assertion of deduced information, may also add additional facts to the knowledge-base.

The taxonomy and slots together constitute the ontology of the theory: what objects and relationships are describable within it.

Micheal S. Hewett
Tue Oct 29 10:54:13 CST 1996