The use of many different simulation systems by the United States Department of Defense has resulted in many different scenario data representations contained in heterogeneous databases. These heterogeneous databases all represent the same data concept, but have different semantics due to intrinsic variations among the data models. In this research, I describe a unified scenario database to allow interoperability and reuse of the scenario data components while avoiding the problems of data redundancy. Using the object-oriented approach, the data and schema of the scenario databases, represented in an object-oriented model, are integrated into a global database also represented in an object-oriented model. The global database schema is extended to allow semantic interoperability of database components by explicitly associating the semantics of the schema elements of the database components with the global metadata. I create the Integration Dictionary to represent the semantic interoperability and to store the translation mappings between each database component and the global database. The Integration Dictionary also provides support for object-oriented views generation. Next, I describe a methodology to integrate databases using the Integration Dictionary. My methodology is based on an analysis of the semantics of conceptual schema elements and on the identification of related elements in the global schema.