Operations on action streams for hypermedia presentation

To support cooperative work of users on computers, use of facilities to record user´s actions is very effective. Furthermore, such records can be required to select the specified actions. We are developing action history view mechanisms that record the action stream of presentation on hypermedia, generate an action history view by applying operations from the recorded action stream, and replay the action history view. Although action history views can be used in various cooperative work, we restrict this to the presentation on a hypermedia environment. In this environment, an action (including voice explaining the material) is recorded as a tuple of a component and an operation to the component. An action stream is defined as a list of recorded actions (tuples). An action history view is a list that contains necessary actions obtained from one or more action streams. The basic way to generate an action history view is to remove the operations related to the unnecessary components or inappropriate components because of security problems. The following functions are expected by presentation systems with action history view mechanisms: asynchronous presentation; reduction of replay time; keeping security; support to create or edit presentations; and synchronous playing of action sequences. We have been developing a prototype system of a hypermedia presentation system realizing the above mentioned operations on action streams