Object-Oriented Data Model Concepts
A key concept of any database system is the data model it is based upon. Object-oriented data models (OODM) try to blend object-oriented concepts as they first emerged in programming languages with concepts from traditional (e.g. network or relational) data models, and at the same time respond to new requirements as they are posed by a variety of “nonstandard” application areas like CAD/CAM, geographic information systems, or office information systems. They are primarily used in object-oriented database management systems (OODBMS ), but even traditional systems are about to adopt some of their features.
In this chapter, we first give a detailed explanation of the notion of data model in general, elaborate on the characteristics and shortcomings of “classical” data models, and motivate the introduction of OODMs. Afterwards, the mandatory and some optional ingredients of OODMs are explained. The chapter concludes by relating the data model to other issues in (object-oriented) database systems, and by discussing the state of the art and probable future developments.
It should be noted that the area of OODMs and systems is still in a phase of development where no general agreement on terms and concepts exists, and thus many variations for individual features can be found in the literature and in systems. The focus of this chapter is to give an introductory overview of the topic; it thus does not aim at a complete coverage of even all major approaches. It also describes the salient concepts in a rather abstract manner instead of referring to any particular system.
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