Today's multimedia content formats primarily encode the presentation of content but not the information the content conveys. However, this presentation-oriented modeling only permits the inflexible, hard-wired presentation of multimedia content. For the realization of advanced operations, the multimedia content has to be enriched by additional semantic information. To provide a basis for the semantic modeling of multimedia content in content sharing and collaborative applications, Enhanced Multimedia Meta Objects (EMMOs) and the query algebra EMMA were developed. Both provide a sound basis for the integration of ontological knowledge. The author demonstrates how ontological knowledge can be used within the authoring process of EMMOs, can be integrated within EMMO knowledge structures, and can be exploited for refining EMMA queries. The book is intended for researchers and developers in the domain of knowledge management, semantic modeling & querying, and multimedia meta modeling. It includes an overview of multimedia meta modeling, introduces the EMMO model and EMMA algebra, and discusses the ontology-enhanced management of multimedia content within different application scenarios.