Abstract: To enable efficient access to multimedia content, the media data has to be augmented by semantic metadata and functionality. The semantic representation has to be integrated with domain ontologies to fully exploit domain-specific knowledge. This knowledge can be used for refining ambiguous user queries by closing the conceptual gap between the user and the information to be retrieved. In our previous research, we have introduced Enhanced Multimedia Meta Objects (EMMOs) as a new approach for semantic multimedia meta modeling, as well as the query algebra EMMA, which is adequate and complete with regard to the EMMO model. This paper focuses on the refinement of EMMA queries by incorporating ontological knowledge.