OBJECT-ORIENTED MODELING OF GEOGRAPHIC DATA

Two levels of data abstraction, namely conceptual and logical, are ess ential in the process of designing an object-oriented geographic datab ase. The aim of the present article is to establish a consistent frame work for this bilevel design. At the conceptual level, we develop an o bject-oriented model useful for organizing the designer's knowledge ab out a geographic application in terms of the basic concepts of the obj ect-oriented paradigm. Both conceptual abstraction primitives (namely, classification, generalization, and aggregation) and a spatial abstra ction primitive (namely, location) are discussed. The dynamic part of the model is due to the methods associated with objects. At the logica l level, we propose an object-oriented structure of classes and instan ces, which is uniform with the conceptual model and, therefore, facili tates the conceptual logical mapping. On the whole, the model-based ap proach adopted in this article offers object orientation, conceptual a bstraction, and system extendibility.