Time and Multimedia Requirements

The problem of synchronising data presentation, user interaction, and physical devices reduces to satisfying temporal precedence relationships under real timing constraints. In this section, we introduce conceptual models that describe temporal information necessary to represent multimedia synchronisation. We also describe language- and graph-based approaches to specification and survey existing methodologies applying these approaches.
The goal of temporal specification is to provide a means of expressing temporal relationships among data objects requiring synchronisation at the time of their creation, in the process of orchestration. This temporal specification ultimately can be used to facilitate database storage and playback of the orchestrated multimedia objects from storage.
To describe temporal synchronisation, an abstract model is necessary for characterising the processes and events associated with presentation of elements with varying display requirements. The presentation problem requires simultaneous, sequential, and independent display of heterogeneous data. This problem closely resembles that of the execution of sequential and parallel threads in a concurrent computational system, for which numerous approaches exist. Many concurrent languages support this concept, for example, CSP and Ada; however, the problem differs for multimedia data presentation. Computational systems are generally interested in the solution of problems which desire high throughput, such as the parallel solution to matrix inversion. On the other hand, multimedia presentation is concerned with the coherent presentation of heterogeneous media to a user. Therefore, there exists a bound on the speed of delivery beyond which a user cannot assimilate the information content of the presentation. For computational systems it is always desired to produce a solution in minimum time. An abstract multimedia timing specification concerns presentation rather than computation.