THE ROLE OF POLYMORPHIC REUSE MECHANISMS IN SCHEMA EVOLUTION IN AN OBJECT-ORIENTED DATABASE

A seamless approach to the incremental design and reuse of object-orie nted methods and query specifications is presented, We argue for avoid ing or minimizing the effort required for manually reprogramming metho ds and queries due to schema modifications, and demonstrate how the ro le of polymorphic reuse mechanisms is exploited for enhancing the adap tiveness of database programs against schema evolution in an object-or iented database. The salient features of our approach are the use of p ropagation patterns and a mechanism for propagation pattern refinement Propagation patterns are employed as an interesting specification for malism for modeling operational requirements. They encourage the reuse of operational specifications against the structural modification of an object-oriented schema. Propagation pattern refinement is suited fo r the specification of reusable operational modules. It promotes the r eusability of propagation patterns toward the operational requirement changes. This approach has a formal basis and emphasizes structural de rivation of specifications. The main innovations are in raising the le vel of abstraction for behavioral schema design, and for making possib le the derivation of operational semantics from structural specificati ons. As a result, both the modularity and reusability of object-orient ed schemas are increased.