Implementation of a Prolog-INGRES interface

This report describes a working prototype of a Prolog-INGRES interface based on external semantic query simplification. Semantic query simplification employs integrity constraints enforced in a database system for reducing the number of tuple variables and terms in a relational query. This type of query simplifier is useful in providing very high level user interfaces to existing database systems. The system employes a graph theoretic approach to simplify arbitrary conjunctive queries with inequalities. One very interesting feature of the system is to provide meaningful error messages in case of an empty query result resulting from contradiction. In addition to data, rules are stored in the database as well and are retrieved automatically if the Prolog program references them but they are not defined in the Prolog rulebase.