Geographic data are increasingly being used in various applications, ranging from location-based services to administrative, public services on the web. To satisfy increased demands for the sharing and exchange of geographic data, a National Spatial Data Infrastructure (NSDI) is needed that supports the utilization of geographic data.

The focus of this thesis is on conceptual modeling approaches and notations that satisfy the special requirements posed by geographic data. Thus, the thesis contributes to an infrastructure for geographic data. First, a requirements analysis is presented that identifies and clarifies several potential research issues. Among the issues investigated in the thesis are the management of geographic entities that are represented multiple times in the same or different databases and modeling of the quality of geographic data, which is of high importance to users.

In the thesis is presented a novel concept for modeling multiply represented entities and their consistent representations. A Multiple Representation Management System (MRMS), which maintains consistency among legacy databases, is outlined. A Multiple Representation Schema Language (MRSL), which is based on an extension to the Unified Modeling Language (UML) and on UML's accompanying Object Constraint Language, is described in detail. The MRSL is used to specify a Multiple Representation Schema (MRSchema) that configures the MRMS. A prototype provides a proof-of-concept.

Finally, the thesis espouses a systematic and integrated approach to the modeling of geographic data and its quality. The approach integrates quality information into the basic model constructs, resulting in what may be considered a quality-enabled model. More specifically, it extends UML with new modeling constructs -- based on standard classes, attributes, and associations -- that include quality information. This model enables designers and users to specify quality requirements in a geographic data model. In addition, a quality-enabled model supports a more application specific distribution of geographic data, e.g., one that uses web services. A case study illustrates the utility of the model.

Further readings:

	A. Friis-Christensen, N. Tryfona, and C.S. Jensen. Modeling Geographic Data-Requirements and Research Issues, in Proceedings of the 9th ACM International Symposium on Advances in Geographic Information Systems, Atlanta, GA, USA, November 9-10, pp. 2-8, 2001.
	A. Friis-Christensen, D. Skogan, C.S. Jensen, G. Skagestein, and N. Tryfona. Management of Multiply Represented Geographic Entities, in Proceedings of the 6th International Database Engineering & Applications Symposium, Edmonton, Canada, July 17-19, pp. 150-159, 2002.
	A. Friis-Christensen, C.S. Jensen. Object-Relational Management of Multiply Represented Geographic Entities, in Proceedings of the 15th International Conference on Scientific and Statistical Database Management, Cambridge, MA, USA, July 9-11, pp. 183-192, 2003.
	A. Friis-Christensen, C.S. Jensen, J.P. Nytun, and D. Skogan. A Conceptual Schema Language for Managing Multiply Represented Geographic Entities. Accepted for publication in Transactions in GIS.
	A. Friis-Christensen, J.V. Christensen, C.S. Jensen. A Framework for Modeling Quality of Geographic Data. Accepted for publication in Proceedings of the 11th International Symposium on Spatial Data Handling.

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