Junehwa Song

Multimedia documents with elastic time

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 de ning temporal relationships among them. If the given specication 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 e ect. 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 exibility in document auThe authors current address is: University of Maryland, College Park, MD 20742, JUNESONG @ CS.UMD.EDU thoring and browsing. The proposed approach has been implemented in Smalltalk/OS2.

Solving systems of difference constraints incrementally

Abstract. Difference constraints systems consisting of inequalities of the form xi - xjn

Modeling timed user-interactions in multimedia documents

leq

Interactive authoring of multimedia documents in a constraint-based authoring system

bi,j occur in many applications, most notably those involving temporal reasoning. Often, it is necessary to maintain a solution to such a system as constraints are added, modified, and deleted. Existing algorithms handle modifications by solving the resulting system anew each time, which is inefficient. The best known algorithm to determine if a system of difference constraints is feasible (i.e., if it has a solution) and to compute a solution runs in Θ (mn) time, where n is the number of variables and m is the number of constraints. This paper presents a new efficient incremental algorithm for maintaining a solution to a system of difference constraints. As constraints are added, modified, or deleted, the algorithm determines if the new system is feasible and updates its solution. When the system becomes infeasible, the algorithm continues to process changes until it becomes feasible again, at which point a feasible solution will be produced. The algorithm processes the addition of a constraint in time O(m + n log n) and the removal of a constraint in constant time when the original system is feasible. More precisely, additions are processed in time O( || Δ || + |Δ| log|Δ| ) , where |Δ| is the number of variables whose values are changed to compute the new feasible solution, and || Δ || is the number of constraints involving the variables whose values are changed. When the original system is infeasible, the algorithm processes any change in O(m + n log n)amortized time. The new algorithm can also be used to check for the existence of negative cycles in dynamic graphs.

Interactive authoring of multimedia documents

Interactive multimedia documents (or systems) can be characterized by active user participation and the diversity of multimedia information accessed at various levels of granularity. They need to support extensive user participation in selecting and tailoring the information and its presentation. Multimedia information fragments may vary from portions of video, pieces of audio, newspaper quotations or chapters of a book. Effectively managing the creation, evolution and complexity of multimedia documents formed by combining media fragments is an essential capability. We consider the hyperstory model of a multimedia document, where a document is structured hierarchically in three dimensions: time, space and asynchrony. The model provides a layered approach in structuring multimedia documents, thus reducing the complexities of large systems. The hyperstory model supports user interactions that are timed, and also supports preemptive resuming. Timed user interactions with the document are modeled with a newly introduced timed Petri-net (TPN*). TPN* is used to infer the behavior of the system. This paper describes TPN*s modeling and analysis and its application to the hyperstory model.

Method for automatically obtaining spatial layout for multimedia presentations

Abstract. As multimedia applications spread widely, it is crucial for programming and design support systems to handle “time” in multimedia documents effectively and flexibly. This paper presents a set of interactive system support tools for designing and maintaining the temporal behavior of multimedia documents. The tool set provides mechanisms for anomaly detection, temporal query processing, and interactive scheduling. It is based on a fast incremental constraint solver we have developed, which can be adapted by any constraint-based system. The incremental constraint solver provides immediate feedback to the user, supporting a highly interactive design process. Combined with existing optimal layout generation mechanisms proposed in the literature, our tools effectively utilize the flexibility provided by constraint-based systems.

System and method for globally scheduling multimedia stories

Authoring multimedia documents involves coordinating various types of media items in time and space. To be effective, authoring requires integration tools that are highly interactive. In addition, the notion of time must be made explicit and flexible so that users may define and manipulate the temporal behavior of documents directly and flexibly. The authors describe an interactive framework for multimedia authoring, which provides users with immediate feedback. It is based on the elastic time model, where the temporal behavior of multimedia documents can be handled explicitly yet flexibly. In its implementation (the Isis* authoring system), users directly manipulate time via timebox diagrams, and the system immediately checks the validity of each user interaction. The system also provides guidance for recovery in anomalous situations. Users can query various temporal properties of the document and use automatic scheduling mechanisms. These system support tools are based on a fast incremental algorithm. Through this approach, multimedia documents can be designed so that they are adaptable to the needs of different users and to changing environments.