System \ Harmony " with Temporal and Active

This paper proposes a multimedia presentation system Harmony which can deal with temporal and active media such as motion video, computer animation, and music sounds. Harmony is based on the notion of a hyperobject which integrates a hypertext system with an object-oriented framework. Each object is considered a node as is usual in hypertext systems, and the relations between objects are represented as links between nodes. Harmony extends the ordinary notion of a link. A link in Harmony consists of three components: objects connected by the link, conditions specifying when the link is navigated, andmessages sent to the target object. In addition to such an extension, each object can include internal objects called subobjects which specify parts of an object and can become a source/destination of a link. Furthermore, the notion of a group object is introduced to represent a synchronization of parallel displayed media information. Through these extended notions of a hypertext model, temporal and active media can be easily handled through the description of temporal relations from the media in hypermedia documents. Based on the design of Harmony, we have implemented a prototype multimedia presentation system which deals with text, music, graphics, motion video, and computer animation as objects. Harmony consists of three subsystems: link manager subsystem (Harmony/LM), user interface subsystem (Harmony/UI), and object-oriented database (Harmony/DB), where a commercial objectoriented database was employed as the Harmony/DB. Scenario viewer was developed for displaying the structure of scenario in a tree graph which can reduce a cognitive overhead in a hypermedia document. The whole system was constructed based on C++ language.