Papers in PDF format

used to specify for instance that information on Bill Clinton is only to be made available when he appears in a
particular video clip (say from 2.17 seconds after the start of that clip, until 8.35 seconds after that start). This
approach can be generalized further, replacing the time information t by a more general condition c . At any
moment during the play-out of o , the elements of x will then be accessible when c evaluates to true.
Another issue specific to time-dependent information in a hypermedia context, is what happens when a new
element becomes current. A number of options exist for the previously current element: this element can
• remain active (play-out of a music clip can continue while the end user consults information about the
composer);
• be suspended (an animation on a chemical reaction can be halted while a student browses information
about a chemical element involved in the reaction; once browsing is finished, the animation can resume
where it was suspended);
• disappear completely (a video clip on a news item becomes irrelevant when the user selects a clip on the
next such item).
In order to deal with these options, the access operator that replaces conventional link following in our
hypermedia data model must be extended.
Although the main focus of this project will be on conceptual modeling issues, we will design and implement a
demonstrator to prove the viability of our concepts. For the server side, we will rely on the HOME hypermedia
server we developed previously [Duval et al. 1995]. For client-side development, we will probably rely on Java.
From our introduction, it should be clear that we consider this approach acceptable for prototyping purposes
only, and that the relevant functionality, once mature, should be integrated in the Web in a more seamless
fashion.
As far as related work in distributed hypermedia is concerned, spatio-temporal synchronisation has received
relatively little attention. Besides the HyTime and MHEG standards, which define interchange formats for
multimedia objects with synchronized components, the Amsterdam Hypermedia Model [Hardman, Bulterman
& van Rossum 1994] and work on the Easy and Harmony viewers for HyperWave [Maurer 1996] are the more
notable exceptions.
Acknowledgment
We gratefully acknowledge the financial support of the Belgian Nationaal ' Fonds voor Wetenschappelijk Onderzoek'.
References
[Duval, Hendrikx & Olivié 1996] E. Duval, K. Hendrikx and H. Olivié. Set-Based Hypermedia Modeling. MMM 96: 3rd
International Conference on Multi-Media Modeling, November 1996.
[Duval et al. 1995] E. Duval, H. Olivié, P. O'Hanlon and D. G. Jameson. HOME: an Environment for Hypermedia Objects.
Journal of Universal Computer Science, 1(5):265-287, May 1995. http://www.iicm.tu-graz.ac.at/Cjucs_root)
(
[Duval, Olivié & Scherbakov 1995] E. Duval, H. Olivié and N. Scherbakov. Contained Hypermedia. Journal of Universal
Computer Science, 1(10): 687-705, Oct. 1995. (http://hyperg.iicm.tu-graz.ac.at/Cjucs_root)
[Ehley, Ilyas & Furht 1995] L. Ehley, M. Ilyas and B. Furht. A Survey of Multimedia Synchronization Techniques. In B.
Furht and M. Milenkovic. A Guided Tour of Multimedia Systems and Applications, pp. 230-256, 1995.
[Hardman, Bulterman & van Rossum 1994] L. Hardman, D. C. A. Bulterman and G. van Rossum. The Amsterdam
Hypermedia Model - Adding Time and Context to the Dexter Model. CACM, 37(2): 50-62, Feb. 1994.
[Maurer 1996] H. Maurer. Hyper-Wave: The Second Generation Web Solution, 1996.