A WFS-based mediation system for GIS interoperability

The proliferation of spatial data on the Internet is beginning to allow a much wider access to data currently available in various Geographic Information Systems (GIS). In order to move to a real Web-based community where geographical data can be accessed and exchanged, we need to provide flexible and powerful GIS data integration solutions. Indeed, GIS are highly heterogeneous: not only they differ by their data representations, but they also offer radically different query languages. A GIS mediation approach should provide (1) an integrated view of the data supplied by all sources, and (2) a geographical query language to access and manipulate integrated data.In this paper we propose an approach that not only focuses on the data integration, but also addresses the integration of query capabilities available at the sources. A GIS may provide a query capability inexistent at another GIS, whereas two query capabilities may be similar but with a slightly different semantics. We introduce the notion of derived wrappers that capture additional query capabilities to either compensate capabilities lacking at a source, or to adjust an existing capability in order to make it homogeneous with other similar capabilities, wrapped at other sources. Finally we describe the implementation of the presented approach that complies with OpenGIS WFS recommendation.