HT99 demo of OHP-Nav, OHP-Tax, etc.

From: Sigi Reich (
Date: Tue 17 Nov 1998 - 09:58:36 CST

Hello everyone,

the deadline for demos for HT99 is approaching fast (Nov. 27th) and therefore we have come up with a proposal for our part of the demo. We would like to demonstrate how services (= computations) work in OHP-Nav, in particular dynamic discovery and invocation of services for sound files.

We understand that other systems (e.g. Construct) may not completely support these features and that their part of the demo may be to demonstrate other aspects of OHP such as collaboration or even other domains. However, we feel that interoperability should always be our ultimate goal and we should work towards it; if we could demonstrate this at the demo as well it would be a wonderful advertisement for the OHSWG.

Here is our proposal:

The Open Hypermedia Protocol (OHP) allows any compliant client program to communicate about hypertext structure with any compliant server. A feature of this protocol is a facility for servers to advertise "services" which they offer over and above the standard hypertext features.

This demonstration will illustrate the services feature with an audio example. The Solent link server [ref] has been extended to understand and deliver sound files, (MPEG-3), and can offer special sound functionality, specifically

Find me associated songs (i.e. files that this file has been linked to) Find me other songs by the same artist Find me cover tracks of this song
Find me other songs on this album (from a pool of songs)

All of these services are achieved by extracting meta information encoded in the MPEG-3 files.

In the demonstration we will show two clients talking to the Solent link server. The first is a dedicated client which has a specialised interface (based on an extended car stereo system). This client expects to find the required services and will fail gracefully if the server cannot provide them.

The second is the The Amphion Media Player [ref] which is an OHP aware extension of the Windows Media Player. This client is a generic media player, and will provide an interface to any services advertised by the current server. We will demonstrate how this client can function with other servers as well as
the server that provides the specialised services discussed above.

This demonstration shows the dynamic discovery and invocation mechanism within OHP which, if supported by generic clients, allows them to access advanced services of which they have no previous knowledge.

-> At this point we would like to demonstrate our generic viewer talking to
other servers, e.g. the Construct server. Would this be possible? Construct would at least need to support the standard services, e.g. follow-link.

For a successful demonstration of this last point it is necessary that we actually talk the same OHP ;-), i.e. we really need to agree on the actual XML specification that is spoken over the wire. We will come up, over the next week, with a modified version of the XML based on the IDL specification that we have mailed out recently (

Any feedback welcome!

Dave & Sigi

Sigi Reich
Multimedia Research Group
Department of Electronics and Computer Science, Bldg. 59 University of Southampton, Southampton S017 1BJ, UK phone +44 (0)1703 59 6505 fax +44 (0) 1703 59 2865 email

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