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Multimedia documents are of importance in several application areas,
such as education, training, advertising and entertainment. Since
multimedia documents may comprise continuous media, such as audio
and video, the presentation of those documents may require a
significant amount of processing and network resources. The amount
of resources available during a presentation depends on the system
configuration and the current system load. Hence, it can happen that
there are not enough resources to render a multimedia document
according to the specification, resulting in a reduced presentation
quality, if the presentation is possible at all. To cope with those
situations, different versions of the same document can be
specified, one for each potential configuration or probable load
situation. A better approach is to have only one document that can
be adapted to different system configurations and load conditions.
To enable this approach, an adaptive document model as well as an
adaptive scheduling algorithm are necessary. In this paper, we
present the adaptive Tiempo document model, an algorithm to check
the consistency of specifications, the concepts of a graphical
document editor supporting the model as well as a scheduling
algorithm which allows to adapt documents conform to our model in
environments with best-effort assignment of resources.
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