Ontological Foundations of Geographical Data

How can data users obtain geographical data that is relevant or at least closely related to their interests? One solution is to understand what geographical data really mean. How to describe the meaning of data? Metadata, which consist of information such as keywords and positional accuracy about the data, seem to solve half the problem. Metadata include geographical terms such as river and mountain, which are used to describe the content of a given geographical data set. These terms, however, are often ambiguous: Two different terms can refer to the same thing [Page 2079]for different people. For instance, river and stream or hill and mountain are different terms that can refer to the same feature. How can one resolve such issues, or at least mitigate the conceptual and terminological differences between the terms, so that when one looks for geographical data about rivers, the data on streams could also be considered? Current approaches, which apply exact string matching, generate only geographical data that are described with the same string. To support information retrieval, the meanings of geographical terms associated with given data should be made explicit. Making the meanings of geographic terms explicit makes it possible to carry out matching to see whether the data involved describe the same thing. This entry discusses the ontological foundations for geographical data. By comprehending its ontological foundations, one is able to describe a geographical term more precisely, which assists in retrieving closely related geographical data.

In what follows, some terms are defined to serve as the background context for the readers, including ontology, ontological commitments, semantic heterogeneity and interoperability, and semantic similarity. Next, the ontological foundations are explored based on the semantic, pragmatic, and spatial aspects of geographic data. On the semantic aspect, the notion of ethnophysiography, which aims to study the semantic meanings of geographical terms in different languages and cultures, is discussed. The study of geopragmatics, which focuses on representing the application contexts of geographical data, is outlined. Last, the notions of bona fide and fiat boundaries of geographic features, and the granularity of geographic space, will be described.