An Ontology-Based Framework for Geographic Data Integration Vânia M.P. Vidal 1 , Eveline R. Sacramento 1 , José Antonio Fernandes de Macêdo 1,2 Marco Antonio Casanova 3 1 Universidade Federal do Ceará, Department of Computing, Brazil {eveline, vvidal, jose.macedo}@lia.ufc.br 2 EPFL - Ecole Polytechnique Fédérale, Database Laboratory, Switzerland jose.macedo@epfl.ch 3 Department of Informatics – Pontifical Catholic University of Rio de Janeiro Rio de Janeiro, RJ – Brazil casanova@inf.puc-rio.br Abstract. Ontologies have been extensively used to model domain-specific knowledge. Recent research has applied ontologies to enhance the discovery and retrieval of geographic data in Spatial Data Infrastructures (SDIs). However, in those approaches it is assumed that all the data required for answering a query can be obtained from a single data source. In this work, we propose an ontology-based framework for the integration of geographic data. In our approach, a query posed on a domain ontology is rewritten into sub-queries submitted over multiples data sources, and the query result is obtained by the proper combination of data resulting from these sub-queries. We illustrate how our framework allows the combination of data from different sources, thus overcoming some limitations of other ontology-based approaches. Our approach is illustrated by an example from the domain of aeronautical flights. Keywords: Keywords: data integration, schema mappings, geographic information retrieval, query processing, Web Feature Service, ontologies. 1 Introduction Spatial Data Infrastructures (SDIs) provide access, reuse and integration of geographic information (GI) from multiple sources. Service providers currently offer access to geospatial data and expose basic processing functionality using Web services technology [1, 2, 3, 6]. This strategy not only offers a standardized, flexible and transparent way to publish underlying data but it also hides details of data access and retrieval from the application. In OGC-compliant SDIs, geospatial data are served via Web Feature Services (WFS). Each WFS offers a feature type schema (FTS), which is the XML schema of the feature type exported by the service. Users can query and update data sources through an FTS. The specifications provided by the