Indexing the Content of Multimedia Documents

As the concept of what constitutes a "content-based" search grows more mature, it becomes valuable for us to establish a clear sense of just what is meant by "content." Recent multimedia document retrieval systems have dealt with this problem by indexing across multiple indexes; but it is important to identify how such multiple indexes are dealing with multiple dimensions of a description space, rather than simply providing the user with more descriptors. In this paper we consider a description space for multimedia documents based on three "dimensions" of a document, namely context, form, and content. We analyze the nature of this space with respect to three challenging examples of multimedia search tasks, and we address the nature of the index structures that would facilitate how these tasks may be achieved. These examples then lead us to some general conclusions on the nature of multimedia indexing and the intuitions we have inherited from the tradition of books and libraries.