Object-oriented modeling of geographic data

Two levels of data abstraction, namely conceptual and logical, are essential in the process of designing an object-oriented geographic database. The aim of the present article is to establish a consistent framework for this bilevel design. At the conceptual level, we develop an object-oriented model useful for organizing the designer's knowledge about a geographic application in terms of the basic concepts of the object-oriented paradigm. Both conceptual abstraction primitives (namely, classification, generalization, and aggregation) and a spatial abstraction primitive (namely, location) are discussed. The dynamic part of the model is due to the methods associated with objects. At the logical level, we propose an object-oriented structure of classes and instances, which is uniform with the conceptual model and, therefore, facilitates the conceptual logical mapping. On the whole, the model-based approach adopted in this article offers object orientation, conceptual abstraction, and system extendibility