Complex objects modeling: An entity-relationship approach

Abstract

Facilities for complex object modeling are nowadays needed in several areas of database applications (CAD/CAM, office automation, robotics, …). Consequently, either new models are developed, or existing ones are extended to better respond to this requirement. Current proposals in the latter category are mainly based on the relational approach (with, as major outcome, the NF2 family of models) or on functional models like DAPLEX. This paper intends to show that the entity-relationship approach may secure an equivalent result, preserving the well known advantages inherent to this approach : increased readability and graphical display of the database schema. To this aim, an enhanced entity-relationship model, called ERC for Entity Relationship Complete, is presented and formally defined. The associated query facilities are presented as well, in the form of an ERC algebra. Finally, the paper discusses how ERC peculiar features (complex attribute structures, multivalued attributes, duplicates) and its algebra succeed in supporting complex object management.