The conventional boundaries separating hypermedia from related disciplines are dissolving to yield a confluence of hypermedia, information retrieval, and multimedia database technologies. Traditionally, query-based retrieval methods have been considered a very different kind of interaction to the browsing commonly associated with hypertext or hypermedia. Queries require prior planning and a more analytical approach with greater cognitive overheads.

Recent research in information retrieval (IR) has endeavored to break down this barrier and build hypertext interfaces to IR systems. Many hypertext-IR retrieval systems have been based on statistical analysis of terms automatically extracted from free text, [Allan96, Dunlop93]; the index space is automatically created and ‘vector space’ similarity coefficients measure degrees of match between queries and media items, or between two media items. A different approach to IR is based on (usually) manually created index spaces, where semantic relationships exist between index terms [Rada93].

One possibility that a semantic index space provides is an organised set of browsable nodes and links as a navigation aid to the associated layer of media items [Agosti95]. The user can browse the index space, ‘beam down’ [Bruza90] to view media items of interest, and conversely ‘beam up’ to the index space from media items, The inclusion of semantic information in the index space, however, provides the opportunity for knowledge-based hypermedia systems that can provide intelligent navigation support and retrieval, with the system taking a more active role in the navigation process rather than relying purely on manual browsing.