Multimedia documents with elastic time

Abstract

Time is an essential component in interactive multimedia documents (or systems). We present the elastic time model for multimedia documents. Using the metaphor of a spring system, it allows authors to associate with each multimedia object a minimum and a maximum length and a length at rest. Authors can connect the (elastic) objects by defining temporal relationships among them. If the given specification is consistent, a document is produced which is also elastic, with a minimum, a maximum, and an optimal length. As such, our elastic model associates with a document a range of feasible solutions in addition to an optimal one. The author can then select from the acceptable range an alternative length for the document, and the system will compute a revised solution that takes the additional global constraint into effect. The system can answer questions, such as: `Can I show this multimedia presentation in 10 minutes? If so, how should all the objects be scheduled?' Furthermore, the system also takes fairness into consideration and distributes any necessary stretching or shrinking across multimedia objects contained in a document. As such, the elastic time model provides expressive power and flexibility in document authoring and browsing. The proposed approach has been implemented in Smalltalk/OS2.