[[abstract]]The advantages of using a formal specification are in its precise definition of object properties and its declarative description of operations of a system. The Z notation is used widely in the literature of formal system designs and the research of language semantics. In line with the rapid growth of multimedia omputation research, we use the Z notation to describe a multimedia database that supports the reuse of multimedia presentations. The database consists of two layers: the frame layer and the resource layer. A frame group in the first layer is the basic presentation unit to be reused. A resource group in the second layer is a collection of resources to be used by a frame, or a frame group. In the hierarchy, we use four ty...