A Structure for Transportable, Dynamic Multimedia Documents

This paper presents a document structure for describing transportable, dynamic multimedia documents. Multimedia documents consist of a set of discrete data components that are joined together in time and space to present a user (or reader) with a single coordinated whole. Transportable documents are those in which the document structure can be accessed across system environments independently of individual component input or output dependencies; dynamic documents are those in which the synchronization of document components are not staticly defined as an integral part of the data definition but are dynamicly defined as attributes of the general document structure. The focus of this paper is the presentation of the basic building blocks of the CWI Multimedia Interchange Format (CMIF). CMIF is used to describe the temporal and structural relationships that exist in multimedia documents. In order to put our work in a concrete context, we start our discussion with a brief description of the portability requirements for documents used within the CWI/Multimedia Pipeline. We then provide a layered description of our document structure format; this format provides a means for expressing a document in terms of synchronization channels, event descriptors, data descriptors, data blocks and synchronization arcs, each element of which contains a set of appropriate descriptive attributes. The paper describes each of these concepts abstractly as well as in the context of a uniform example. The paper concludes with a discussion of our intended future direction in using the various attribute descriptors to control a broad range of activities within the CWI/Multimedia Pipeline.