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will treat application or system events has to be defined. The related applica-
tion domains are challenging and demanding. These applications include,
among others, interactive TV, digital movies, and virtual-reality applications.
In the framework of IMDs, we consider events, spatiotemporal composition,
and the scenario as cornerstone concepts in a modeling effort.
Events are the fundamental means of interaction in the context of
the IMD and are raised by user actions, by objects participating in
the IMD, or by the system. They can be simple (i.e., not decompos-
able in the IMD context) or complex, and they have attached their
spatiotemporal signature (i.e., the space and the time they occurred).
For more details, refer to [5].
·
Spatiotemporal composition is an essential part of an IMD and rep-
resents the spatial and temporal ordering of media objects in the cor-
responding domain. At this point, the issue of spatial and temporal
relationships among the objects is critical [6].
·
The scenario stands for the integrated behavioral contents of the
IMD, that is, what kind of events the IMD will consume and what
presentation actions will be triggered as a result. In our approach, a
scenario consists of a set of self-standing functional units (scenario
tuples) that include triggering events (for start and stop), presenta-
tion actions (in terms of spatiotemporal compositions) to be carried
out in the context of the scenario tuple, and related synchronization
events (i.e., events that get triggered when a scenario tuple starts or
stops).
·
To support complex IMDs, a system that offers both a suitable high-level
modeling of IMDs and interactive multimedia presentation capabilities is
needed. The modeling should provide for the spatial and temporal composi-
tion of the participating media, the definition of interaction between the user
and the IMD, and the specification of media synchronization.
We claim that modeling of IMDs should place more emphasis on the
interactive parts of such an application. In principle, the modeling of interac-
tion should cover all the procedures that somehow involve the machine and
the user.
8.3.1.1 Modeling Interaction With Events
The concept of events is defined in several research areas. In the area of active
DBs an event is defined as an instantaneous happening of interest. An event is
