The operational semantics of user-defined relationships in object oriented database

In semantic data models, abstract relationslúp ( e.g. generalization, aggregation, etc) semantics is defined specifying how insertion, deletion and modification operations made at a higher abstraction level can a.ffect the object abstracted and vice versa. This semantics, also know as structural constraints, is expressed through the so-called update rules. This perspective is somehow fade out in most object-oriented systems where user-defined relationslúps are supported as simple pointers and their semantics are embedded, distributed and replicated within the operations accessing these pointers. Tlús paper inherits and extends the treatment of relationships found in semantic data models to behavioural object-oriented models by presenting an approach to uniformly capture the update rules for user-defined relationships. The stress is not on supporting relationships as first-class objects but on describing their update rules ( or operational semantics) through a set of constructors namely, reaction, anticipation, delegation and exception. The approach has been born out by an implementation in an active object-oriented databa.se system