Mapping an Extended Entity-Relationship Schema into a Schema of Complex Objects

With the advent of object-oriented database systems, there is an urgent need to define a methodology for mapping a conceptual schema into an object-oriented one, and migrating from a conventional database to an object-oriented database containing complex objects. This paper deals with an important step of the migration process by describing a technique for complex entity formation which involves recursively grouping entities and relationships from an extended entity-relationship schema, using semantic abstractions such as aggregation, generalization and association. The abstract schema produced by the clustering technique at a given level of grouping can then be converted into a structurally object-oriented schema allowing the explicit expression of complex entity types, relationships and integrity constraints. The overall methodology is implemented within the environment of INTER-SEM, a prototype for semantic object-oriented modelling.