Composition is essential in the research of formal specifications. It facilitates the design, synthesis, testing and reuse of large programs. In order to facilitate users to specify the temporal specification at the time of authoring a multimedia program, a composition model is needed. Recently various such models have been proposed in literature, which include language-based model, graphical model, time-interval based model, object-oriented model, etc. However, most of these models are lowly abstract and it is difficult to support the composition of two multimedia programs. In this paper, by introducing a new concept unit stream and extending two temporal relations, the structuring technique is studied in order to allow complex multimedia programs to be structured, making them understandable for designers, and to allow multimedia programs to be authored in terms of composition of general purpose multimedia programs that can be re-used in authoring various different multimedia programs.