Extensions to the object-oriented paradigm

It is argued that present object-oriented (O-O) database management systems (DBMSs) have not gone far enough. Two important aspects of semantics are not captured in the Smalltalk-type O-O paradigm and the DBMSs that have been developed on the basis of this paradigm. The first aspect is the specification of knowledge rules which model constraints, expert knowledge, deductive rules, and trigger conditions that are applicable to objects. The second aspect is the specification of various types of associations that an object type can have with other object types. It is suggested that the O-O paradigm for future database or knowledge-base management systems should extend the concept of a class from that of object type to object class. Rule declaration, rule inheritance, and association types are discussed