Part-Whole Relationship Categories and Their Application in Object-Oriented Analysis

Part decomposition and conversely the con struction of composite objects out of individual parts have long been recognized as ubiquitous and essential mecha nisms involving abstraction This applies in particular in areas such as CAD manufacturing software development and computer graphics Although the part of relationship is distinguished in object oriented modeling techniques it ranks far behind the concept of generalization specialization and a rigorous de nition of its semantics is still missing In this paper we rst show in which ways a shift in emphasis on the part of relationship leads to analysis and design models that are easier to understand and to maintain We then in vestigate the properties of part of relationships in order to de ne their semantics This is achieved by means of a cate gorization of part of relationships and by associating seman tic constraints with individual categories We further sug gest a precise and compared with existing techniques less redundant speci cation of constraints accompanying part of categories based on the degree of exclusiveness and depen dence of parts on composite objects Although the approach appears generally applicable the object oriented Uni ed Modeling Language UML is used to present our ndings Several examples demonstrate the applicability of the cate gories introduced Index terms Conceptual modeling object oriented analysis object oriented design part of relationship part of relationship cat egories partonomy aggregation semantic constraints object life