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Hypermedia systems structure large quantities of multimedia information into webs of associated concepts. Users can selectively explore these concepts, limiting the quantity of information viewed to suit their personal goals for using the system. But the flexibility of navigational freedom creates a problem for hypermedia designers--that of incorporating mandatorily viewable information into the web. One frequently used solution is to script information illustrating multiple levels of detail into a single non- interruptable presentation to be associated with a single node of the web. This technique affords the designer control over what the user sees, yet does so at the expense of the user's control over time spent with the system. This paper addresses the need for adaptivity at the presentation-level in hypermedia systems. A two-component system is described for the authoring and temporal adaptation of multimedia scripts used in hypermedia applications. With the authoring component, a user (taking on the role of hypermedia designer) can design multimedia presentations using text, still images, sound, animation and video objects. Using graphic interfaces, the user can format these objects in space and time, modify their media-specific attributes, and semantically delineate these objects as pertaining to specific levels of detail. This delineation creates hierarchical structures which can then be selectively parsed by the system to create variations on the original presentation. The user can save all formatting and chunking decisions in a script, creating a persistent record of the presentation. These scripts can then be associated with the nodes of a hypermedia system, so that when a hypermedia user invokes a node, some version of the scripted presentation is played back. The hypermedia component is responsible for determining version content of a presentation. Based on user-imposed constraints (hypermedia users can dynamically input how much time they wish to spend with the system, as well as interest levels associated with represented concepts), the system can adjust the amount of detail shown in a given presentation, thus contracting or expanding the presentation over time.
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