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Identity-Based Change Operations for Composite Objects∗

Incorporating abstraction methods, such as aggregation and association, into information system design methodologies has improved our ability to model the real world. The semantically-higher level objects that result from these abstractions are referred to as composite objects. These objects play an important role in spatio-temporal knowledge representation and query formulation, although little has been done so far on formalizing operations involving these types of objects. In this investigation, the semantics associated with composite objects are explored as is the role of object identity for composite objects. Object identity refers to that trait which distinguishes an object from all others. The different semantics associated with creating composite objects and adding parts to composites are discussed and a set of basic identity-based change operations for composites, including separation and elimination operations, are described. Formalizing the operations relating to composite objects aids in improving current spatial data models and leads to advances in spatial-temporal query languages.