Towards a geospatial catalogue federation service

As geospatial catalogues are becoming accessible online through public query interfaces, a federation to fulfill distributed and integrated metadata discovery needs to be built. This study investigates the feasibility of federating three distinct geospatial catalogue services: the NASA Earth Observing System (EOS) ClearingHOuse (ECHO), the George Mason University (GMU) OpenGIS Catalogue Service for Web (CSW), and the U.S. Department of Energy (DOE) Earth System Grid (ESG) Simulation Data Catalogue. Challenges and problems in dealing with the metadata conceptual models, query languages, and communication protocols are analyzed. Proposed federation strategies and the operational federation system are introduced. Our results show that protocol adaptation, query dispatching, query criteria translation, and query results integration are the four main challenges in building a catalogue federation. A mediator-wrapper based approach can be adopted to build a federation service, The OpenGIS Catalogue Service specification can be used to define the internal communication protocols between the federation service and the affiliated catalogue services, and between the federation service and its clients.