A Vision for Open Hypermedia Systems Nürnberg and Leggett

2.1 Open Hypermedia Systems

Open. The term open has been used to mean many things in system work. The consensus of the OHSWG has been that open hypermedia systems allow an open set of clients of the hypermedia services provided by the system. No assumptions about the clients (such as data types handled, etc.) are made.

Hypermedia. The term hypermedia (somewhat surprisingly) has not been well-defined by the group. Furthermore, it is not clear that the group's members agree on what it constitutes. Proposals to the group touching on this subject have varied widely, from a "minimalist" approach, as argued in the current protocol proposal [Davis et al. 1996], to a somewhat broader view, as argued in [Trigg and Grønbæk 1997]. This range of opinions may stem from the fact that the systems represented in the group have widely varying notions of those services that should be provided by a hypermedia system. DHM [Grønbæk and Trigg 1996] includes composite services. Microcosm [Davis et al. 1992] includes information retrieval services. HOSS [Nürnberg et al. 1996] provides taxonomic, spatial, and other structural services. The exact types of services to be provided by an OHS must be resolved before any real progress can be made on the architecture and proposal. We present our view on this subject below.

System. Even this most innocuous term can cause a bit of confusion. Wiil and Leggett [1996] described a division of OHS's into two categories. Open link services (e.g. Chimera, Microcosm, Multicard) are systems that concern themselves primarily with the provision of hypermedia functionality (whatever that may be) to third party applications. Open hyperbases (e.g. DHM, HyperDisco, HOSS) provide open link services and some notion of hypermedia storage. Obviously, the OHSWG must make decisions regarding the presence or absence of hypermedia-based storage in any OHS reference architecture. Additionally, some systems provide a much higher degree of distribution than others, and thus must account for "secondary" services such as location services, naming, etc. The questions of which of these kinds of secondary services should be included in an OHS also must be addressed. We present our views on this subject below as well.


Peter J. Nürnberg, John J. Leggett
HRL, CSDL, Texas A&M
original page URL: http://jodi.ecs.soton.ac.uk/Articles/v01/i02/Nurnberg/scope_ohs.html