Entity-relationship Modeling of Spatial Data for Geographic Information Systems

This article presents an extension to the basic Entity-Relationship (E-R) database modeling approach for use in designing geographic databases. This extension handles the standard spatial objects found in geographic information systems, multiple representations of the spatial objects, temporal representations, and the traditional coordinate and topological attributes associated with spatial objects and relationships. Spatial operations are also included in this extended E-R modeling approach to represent the instances where relationships between spatial data objects are only implicit in the database but are made explicit through spatial operations. The extended E-R modeling methodology maps directly into a detailed database design and a set of GIS function.