A general concept for the representation of multimedia data by unformatted and formatted data is introduced. It leads to a basic-function approach to the design and development of multimedia database systems, which extends a relational database management system with new attribute types. In this paper, raster (or bitmap) images are used as an example. The structure of image values is defined, and a basic set of operations for access and manipulation is proposed. These operations can be integrated into a query language like SQL. To facilitate a contents-oriented search on multimedia data in general and on images in particular, text descriptions are introduced into the database that allow users to indicate the contents of an image. The well established techniques of information retrieval can be applied to search for these descriptions. The proposed system allows us to model images that are assigned to objects as well as stand-alone images. The paper finally sketches a prototype implementation on top of an existing relational database management system (Ingres). Keywords: Multimedia databases, Image databases, Theses. (mjm)