Modelling geographic data with multiple representations

Abstract The impact of resolution has been widely studied on raster data, exploring new ways to store and use raster data at different resolution levels. A similar amount of work has not yet been achieved for vector data. The aim of this paper is to propose a framework suitable for vector data for use at different resolution levels. The framework has in fact a wider scope as it has been designed for the general problem of using multiple representations of geographical and thematic data. This problem can be divided into three main issues: data modelling, data matching from different data sets, and data utilization. How can geographical phenomena with several representations be modelled in vector geographic information systems (GIS)? How should different representations be matched to make the data-management systems aware that they all represent the same geographical phenomenon? How can systems supporting multiple representations be used? Answers to these questions have been elaborated as part of the European MurMur project. They are presented here and illustrated using current applications from the French national mapping agency (IGN). Acknowledgements The authors wish to express their thanks to François Vauglin, who initiated work on this paper before he left the IGN, and the MurMur project. We also thank all the MurMur partners. Notes 1MurMur, Multiple Representation–Multiple Resolution, EEC 5th Framework project IST-1999-10723 (2000–2002). The project partners were IGN, Cemagref, Star Informatic, Université Libre de Bruxelles, University of Lausanne and Swiss Federal Institute of Technology, Lausanne. The project has been supported by EEC and the Swiss government (OFES). http://www.mur-mur.org 2In this paper, we adopt the database terminology, which refers to the description of data in a database as the database schema, and to the set of modelling concepts (object type, attribute, etc.) as the data model. In GIS applications, the database schema is often referred to as the database model, and the data model is called the meta-model. 3Overloading an attribute of a class is an object-oriented mechanism that defines in a sub-class a new value for this attribute. Whenever a user accesses the attribute, they get the value defined in the super-class (respectively sub-class) if they are accessing the object instance as a member of the super-class (respectively sub-class).