Abstraction forms in object-oriented conceptual modeling: Localization, aggregation and generalization extensions

Abstract

This paper proposes abstraction mechanisms in the field of object-oriented conceptual modeling. It introduces new abstraction form of localization principle and extends existing ones aggregation and generalization - to make them suitable to recent advances in object-oriented approaches. Localization is a principle for encouraging the design of object properties in isolation from other objects. Currently a large variety of object-oriented models support the localization principle by means of object structure and object behavior. Typically the object structure consists of a set of attributes. The object behavior is defined as a set of events. The object life cycle construct is introduced as an abstract representation of all possible event sequences on the object. Aggregation is used to put objects together in order to build larger objects and to control the resulting behavior of these complex objects. Usually aggregation is used as an object structuring mechanism, we propose to apply aggregation to events as well. Event aggregation is a useful mechanism for relating the behavior of complex objects with the behavior of their constituent objects. Generalization is introduced to organize both object classes and object states into hierarchies. Classes and class hierarchies allow the stepwise organisation of similarities and differences between objects. States and state hierarchies allow to organize the similarities and differences of an object at various points of time in its life cycle in a controlled manner.