Integration von Sorten als ausgezeichnete taxonomische Prädikate in eine relational-funktionale Sprache

Abstract

Sorts are incorperated into RELFUN as distinguished unary predicates usable as first-class citizens. Inheritance is integrated into the unification process via a taxonomy defined by a partial-order relation on the sorts. Sort knowledge describes which individuals belong to a sort (ABOX) and which order dependencies exist between the sorts (TBOX). This special knowledge should be recognizable as such. The separation can be reached by a special (second-order) predicate subsumes or by partitioning the knowledge base. Focusing on partitioning, we can choose a dynamic (run-time) or static (compile-time) model for the unification involving sorted terms. In the static model a precompiler generates an internal structure representing the refiexive-transitive sort closure and the defined individuals of each sort. Using this structure, unification is reduced to list intersectiom (sort-sort unification, succeeding with the glb) 01' a membership test (sort-individual unification). It also provides elementary validation operations for taxonomy acylicity, unique glb's, and the equivalence of intensional (TBOX) and exensional (ABOX) glb's.