Resolving Semantic Heterogeneity in the Indian NSDI: An Ontology Mapping Approach Sumit Sen Deptt of Computer Science, IIT Bombay and 2IfGI, University of Münster, Germany, India Email: sumitsen@uni-muenster.de Suman Somavarapu, N.L Sarda Deptt of Computer Science, IIT Bombay, Interoperability is a core requirement for effective data sharing in the NSDI. This paper discusses syntactic interoperability using XML based technologies and GML standards. Role of Database Schemas and their role in interoperability is discussed in the context of a semantic matching tool and the use of ontology based matching of concepts is elaborated. Finally we identify some directions for efforts in the Indian NSDI and outline the need for further experimentation. Keywords: Interoperability, Semantic matching, ontology, database systems.