AN OODB PART-WHOLE MODEL - SEMANTICS, NOTATION AND IMPLEMENTATION

The notion of a part-whole relationship plays an important role when m odeling data in many advanced application domains. It is therefore imp ortant that Object-Oriented Database (OODB) systems include support fo r this modeling primitive. We present a comprehensive part model for O ODB systems. The model's foundation is a part-whole relationship that captures a variety of real-world, part-whole semantics, partitioned in to four characteristic dimensions: exclusiveness, multiplicity, depend ency and inheritance. These impose constraints on any 'part' transacti ons (like 'add-part') to ensure that the state of the database remains consistent with the prescribed part-whole semantics. They also provid e functionality like deletion dependency and several kinds of inherita nce, both from the part to the whole and vice versa. The part relation ship gives flexibility to an application developer who simply declares the desired semantics and then lets the OODB system automatically enf orce it. We also introduce a graphical notation that can be used to ex press the enhanced semantics in the development of OODB part-whole sch emata. Our part model has been integrated into the VODAK Model Languag e (VML), an OODB system, with the use of its extensible metaclass mech anism. (C) 1998 Elsevier Science B.V.