20. An apparatus for enforcing a referential integrity constraint between a constraint set of objects and constrained object having values that are terms of an ontology in a relational database management system, the objects in the constraint set being possible values in the constrained object and the relational database management system being implemented in a workstation having a processor and a storage device to which the processor has access and the apparatus comprising: the storage device having an association between the constrained object and the constraint set of objects, the constraint set of objects having been returned by an ontology query that is executed in the relational database system and returns the objects in the constraint set to be used to define the referential integrity constraint, wherein different constraint sets can be derived by querying the same ontology, the constrained object comprising a constrained column that is defined in the relational database management system; the constraint set associated with the constrained object is a term object with a column, values in the column being the members of the constraint set; and a referential integrity constraint for the constrained object which references the column in the term object; and the processor for executing a constraint enforcer which, when an operation in the relational database management system adds a value to the constrained object, permits the operation only if the added value is a member of the constraint set, and when a modification is performed on the ontology in the relational database management system that results in a different set of values being returned by the ontology query, altering one or more values in the constrained object that are not contained in the different set of values.
22. The apparatus set forth in claim 20 wherein the term object comprises a materialized view.