Kripa Joshi

Date of Award

12-2007

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Spatial Information Science and Engineering

Advisor

Kathleen Stewart Hornsby

Second Committee Member

M. Kate Beard-Tisdale

Third Committee Member

Max J. Egenhofer

Abstract

Publicly available ontologies are growing in number at present. These ontologies describe entities in a domain and the relations among these entities. This thesis describes a method to automatically combine a pair of orthogonal ontologies using cross products. A geospatial ontology and a temporal ontology are combined in this work. Computing the cross product of the geospatial and the temporal ontologies gives a complete set of pairwise combination of terms from the two ontologies. This method offers researchers the benefit of using ontologies that are already existing and available rather than building new ontologies for areas outside their scope of expertise. The resulting framework describes a geospatial domain over all possible temporal granularities or levels, allowing one domain to be understood from the perspective of another domain. Further queries on the framework help a user to make higher order inferences about a domain. In this work, Protege, an open source ontology editor and a knowledge base tool, is used to model ontologies. Protege supports the creation, visualization and manipulation of ontologies in various formats including XML (Extensible Markup Language). Use of standard and extensible languages like XML allows sharing of data across different information systems, and thus supports reuse of these ontologies. Both the geospatial ontology and the temporal ontology are represented in Protege. This thesis demonstrates the usefulness of this integrated spatio-temporal framework for reasoning about geospatial domains. SQL queries can be applied to the cross product to return to the user different kinds of information about their domain. For example, a geospatial term Library can be combined with all terms from the temporal ontology to consider Library over all possible kinds of times, including those that might have been overlooked during previous analyses. Visualizations of cross product spaces using Graphviz provides a means for displaying the geospatial-temporal terms as well as the different relations that link these terms. This visualization step also highlights the structure of the cross product for users. In order to generate a more tractable cross product for analysis purposes, methods for filtering terms from the cross product are also introduced. Filtering results in a more focused understanding of the spatio-temporal framework.

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