Formal Models to Compose and Execute Interactive Multimedia Scores in Real-Time
Résumé
Nowadays, the design of interactive multimedia systems based on a written scenario is a challenge that requires to handle dynamic and static events as well as dynamic and static data. Interactive scores (IS) [8] propose a model to write and execute interactive scenarios comprised of several multimedia processes. In IS, multimedia processes are temporal objects, represented as boxes, whose temporal organization is defined by asserting temporal relations those objects should obey. IS may also contain interactive points. These are used as triggers to modify temporal relations during execution. An important requirement of this model is that the temporal constraints defined by the composer must be preserved during the execution of the scenario.
Currently, the software i-score implements the model described above in a visual environment. Its execution model is based on Hierarchical Time Stream Petri Nets (HTSPNs) [11]. Places and transitions of Petri nets model temporal aspects of the scenario (i.e., they define a partial order between static and dynamic events) defined during its composition. Such implementation provides an efficient and safe execution, but implies some limitations: (1) it presents a quite static structure and doest not support dynamic creation of processes; (2) it does not support conditionals and loops; (3) it cannot handle complex data; and (4) the visual language complicates the representation of some abstract programming concepts such as control structures, recursion and variables, and also limits the ability of expression in the temporal organization of scores. In this poster, we present some approaches to overcome the above limitations in the execution model of i-score.
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