Modal navigation for hypermedia applications

Hypermedia applications combine the flexibility of navigation based-access to information, typical of hypertext, with the communication power of multiple media, typical of multimedia systems. By their very nature, hypermedia applications support multimode interaction, i.e., interaction based on a combination of multiple modalities that are induced by different media and different navigation paradigms. The potentially huge number of mode combinations in hypermedia can accommodate a large variety of user needs and tasks. Multimode interaction, however, is intrinsically complex for the users if several multimode paradigmas coexist within the same application. This paper discusses the concept of modal navigation as a technique that allows to achieve both simplicity in user interaction and flexibility in tuning navigation styles to specific needs of different categories of users. According to modal navigation, the semantics of navigation commands depends upon the current setting of modes. Various paradigms are discussed for modal navigation that take into account different degrees of user's control in the definition of mode configuration and mode resetting. The approach will be exemplified by discussing a real life hypermedia application under development at HOC in cooperation with the Poldi Pezzoli Museum in Milano.