UGML: an extension of GML to provide support for geographic objects with uncertain boundaries

Ashley Morris 1and Frederick E. Petry 2
1 DePaul University
School of Computer Science
243 S Wabash Ave, Chicago IL, 60604, USA
Tel.: 1 312 362 8252
2 Naval Research Laboratory
Stennis Space Center, MS, 30529, USA

The GML (Geographic Markup Language) as created by the Open Geospatial Consortium has emerged as the standard for spatial data interchange. Whether objects are to be stored in a relational database, an object oriented database, or a file, they can be exchanged if they are encoded in the GML format. The designers of GML realized that by basing GML on XML (eXtensible Markup Language), users could then extend the language to provide additional support for spatial objects that are not explicitly defined by the original GML specifications. In this paper, we discuss how the GML can be extended (using the XML schema format), to fully support objects with uncertain boundaries using the framework outlined in our prior work (Morris 2003). The basis of our framework is that by using fuzzy logic, we can provide for indeterminate boundaries for any geographic object. We may store a number of alpha-cuts (a crisp subset of a fuzzy set) for each spatial object (1 only if the object has a crisp boundary), and each alpha-cut representation of that object will represent the boundary of that object with a certain degree of membership. The user may then define any number of alpha-cuts for each spatial object, depending upon the degree of precision they require. This UGML (Uncertain GML) implements this multiple alpha-cut framework within the GML specification.

Keywords: OpenGIS, fuzzy logic, uncertainty, GML

In: Caetano, M. and Painho, M. (eds). Proceedings of the 7th International Symposium on Spatial Accuracy Assessment in Natural Resources and Environmental Sciences, 5 – 7 July 2006, Lisboa, Instituto Geográfico Português

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