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Constraint Management.

Provision of a general purpose constraint system within MADE for all of the potential uses of constraints in a multimedia development environment would justify a development project in its own right. Fortunately, there are various restricted types of constraint satisfier that, while not being as capable in some aspects, still provide useful functionality for dealing with certain categories of constraint.

The approach followed in the specification of constraints within MADE (see also [30]), is to consider those applications of constraint systems that are of direct relevance to the multimedia part of MADE. In effect, this restricts the scope of the constraint satisfier to the topics of geometric layout, user interface control, animation, and media synchronisation. For example, the MADE presentation facilities include a composition editor/player which may make use of constraints when defining the hypermedia document structure and presentation characteristics. What this classification means is that any predefined constraints that are defined as part of the toolkit can be organised into ``constraint families'' (to avoid the use of the term ``class'') which are relevant for specific multimedia aspects.

For the time being at least, only one-way constraints are proposed for MADE. While multi-way constraints provide greater expressive power to the constraint user, they also require more complex constraint satisfaction algorithms and may involve more effort on the part of the programmer to set up specific constraint objects. This decision need not be considered final, and can be reviewed after experience with the proposed constraint objects has been gained.

Next: Utilities Up: Combination Objects Previous: Interaction Objects.
Tue Jan 25 14:21:49 MET 1994