Special requirements are identified that arise in the handling of multimedia data. Individual objects, e.g., documents, should be extendable beyond their types. Data dispersed over several databases must be integrated and handled uniformingly. A clear distinction is to be drawn between the (internal) modelling and the (external) presentation of multimedia objects. Data model constructs should be provided to define various semantic relationships, such as roles, copies, and versions. A reference architecture for multimedia databases is introduced and the requirements are associated with the different components of this architecture. It is shown, how object-oriented data models can be used and extended to meet the requirements set out above. In particular, the metaclass concept is proposed to provide at the meta level those features of the data model that are needed to handle multimedia applications.

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