A Multimedia Constraint System (or: do we have it MADE)

The MADE constraint system provides excellent opportunities to introduce constraints in a multimedia application. Multimedia applications are not only a good place to experiment with constraint systems; constraints in a multimedia environment are almost indispensable. Due to the overwhelming amount of data and the number of relations between several parts of this data, multimedia applications almost demand the support of a constraint management system. The MADE constraint system combines the object oriented programming paradigm, inherited from the mC++ language, the declarative constraint programming paradigm and the special requirements imposed upon the constraint system by the multimedia environment. Among other things, the MADE constraint system provides parallel satisfaction techniques; several constraints may be solved simultaneously and this satisfaction process is performed in parallel with the application.This not only reduces the time needed to solve the constraints, it also allows the multimedia application to proceed with its presentation while (beneath the surface) the constraints are maintained. This not only holds for the parts of the presentation that are not constrained at all, but also for those parts that are. Furthermore, the constraint system is transparent to the multimedia application; no special coding or preparation of the objects in the application is necessary. Constraints can be added later to the application without much work. Besides that, it is also possible to add and remove constraints at runtime; objects may be constrained for only a period of the time the application is running. Introduction This paper discusses the constraint system developed for the MADE programming environment. This discussion will deal with terminology as used in MADE, the several different flavours of constraints in MADE, how to create them, the way in which the constraint system maintains the different constraints and some results regarding the effectiveness of the constraint system (section 2.1-section 2.3). We begin with a review of constraint systems and the requirements for constraint systems in multimedia applications. 1.1 Constraint Systems in General Constraints specify dependency relations between 'things'. The nature of these 'things' very much depends on the environment in which the constraints are used. Typical areas in which constraints are used are user interface control [Borning et al. 86], [Maloney et al. nature of these 'things' is not of particular interest to us; in the remainder of this text, we will address these 'things' as objects and assume that each object has at least one property which has a value that …