-Ontologies are becoming increasingly popular due to recent efforts to extend the capabilities of the World Wide Web through the addition of formal semantics. While ontologies have traditionally been used as precise languages to facilitate efficient exchange of information among people, the "Semantic Web" is extending this role to software agents. For this to be possible, ontologies must be formalized in languages processable by computers, such as OWL, the W3C's Web Ontology Language. The purpose of OWL ontologies is to permit software agents to understand web content and to interact intelligently with Web services (which may themselves be software agents). The use of such ontologies, however, need not be constrained to the Web. Recently, ontologies have found their way into higher-level information fusion where they are providing a means for describing and reasoning about sensor data, objects, relations and general domain theories. To the best of our knowledge, there is as of yet no documented effort to capture the main uses of ontologies in information fusion. In this paper we start filling this void by presenting a number of "use cases," i.e., scenarios of the use of ontologies in the context of higher-level information fusion. In this paper we develop use cases in which ontologies are used both for the fusion process itself and for the development of fusion systems. The use cases cover scenarios in which the agent roles are played by people, software or both.