National Center for Geographic Information and Analysis

This paper addresses the problem of formalizing the natural-language definitions of spatial features. While the Spatial Data Transfer Standard (SDTS) supports the structural aspects of the definition of spatial features, it falls short of providing means to convey explicitly their behavior. An approach using functional algebra is developed using the example of the SDTS standard entity types “dam,” “watercourse,” and “lake,” together with the operations expressed in the natural-language definitions of these features. Formal algebraic specifications go beyond the SDTS approach, by providing precise mathematical representations of the behavior of geographic features and the interactions among related feature types. Functional specifications also help in refining the selection of attributes needed to characterize the behavior of a given feature type. An implication of the functional approach is to provide precise mathematical signatures of feature types as an alternative to natural-language definitions. Mathematical specifications are unambiguous across cultures and languages and provide a strict basis for assessing the interoperability of objects in feature-based GISs.