Term indexing for retrieval by unification

A method is presented for indexing terms in a knowledge-base retrieval-by-unification (RBU) system. The term is a well-defined structure which represents knowledge using variables. RBU operations are an extension of relational database operations using unification and backtracking to retrieve terms from term relations. The term indexing proposed uses hashing and trie structures to reduce the number of comparisons between elements of a search condition and of an object term relation. Unification on a trie structure is suited to backtracking bindings of variables. The search and updating speed of an RBU prototype is measured to evaluate the indexing method. This method is effective for fast term retrieval for a large number of similar and varied form terms. The overhead for maintaining indexes in updating is low