An ontological structure for semantic interoperability of GIS and environmental modeling Gholam Reza Fallahi a, * , Andrew U. Frank b,1 , Mohammad Saadi Mesgari a,2 , Abbas Rajabifard c,3 a Geodesy and Geomatics Eng. Faculty, K.N. Toosi University of Technology, Tehran, Iran b Institute for Geoinformation and Cartography, Technical University of Vienna, Austria c Department of Geomatics, Centre for Spatial Data Infrastructures and Land Administration, The University of Melbourne, Victoria 3010, Australia Received 6 May 2007; accepted 21 January 2008 Abstract Service-oriented architecture in a distributed computing environment, with loosely coupled geo-services is a new approach for using GIS services in environmental modeling. The messages exchanged must follow a set of standard protocols which support syntactic interoperability, but do not address application semantics. This article proposes a layer-based ontology with additional layers for describing geo-services, especially the measurement units used. The paper gives an ontology of measurements for describing the input and output of field-based geo-services and a core ontology of geo-services containing the domain concepts. An upper ontology adds new general concepts to an existing ontology in order to achieve an agreement between geo-service developers and environmental modelers. The layer-based structure is the building block for discovering geo-services that support semantic interoperability in GIS and environmental modeling. # 2008 Elsevier B.V. All rights reserved. Keywords: GIS; Geo-service; Semantic interoperability; Ontology 1. Introduction The natural environment includes physical pro- cesses such as surface flow, soil erosion and infiltration. Scientists model physical processes and impacts of human activities on the natural environ- ment for prediction and analysis of relationships among phenomena affecting the environment. A model is a formal representation of the relationships between defined quantities or qualities (Jeffers, 1982). Some of the defined quantities or qualities in environmental models have a spatio-temporal nature. Thus, environmental modelers use GIS for describing the models of how the environment changes (e.g., models of erosion, flooding, vegetation growth and changes, urbanization). Currently, different approaches are being used to link GIS and environmental models. Goodchild (2001) classifies these approaches into: (1) full integration (embedding), (2) tight coupling, (3) loose coupling. www.elsevier.com/locate/jag International Journal of Applied Earth Observation and Geoinformation 10 (2008) 342–357 * Corresponding author. Tel.: +98 21 66071070; fax: +98 21 66071000. E-mail addresses: fallahi@ncc.neda.net.ir (G.R. Fallahi), frank@geoinfo.tuwien.ac.at (A.U. Frank), Mesgari@kntu.ac.ir (M.S. Mesgari), abbas.r@unimelb.edu.au (A. Rajabifard). 1 Tel.: +43 1 58801 12710; fax: +43 1 58801 12799. 2 Tel.: +98 21 8786215; fax: +98 21 8786216. 3 Tel.: +61 3 834 40234; fax: +61 3 9347 2916. 0303-2434/$ – see front matter # 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jag.2008.01.001