Context-aware hypermedia in a dynamically-changing environment, supported by a high-level Petri net

In modern hypertext systems, with the increased availability of personal computers with environmental sensors (e.g., GPS sensors), adaptation support to meet the needs of the users in dynamically-changing environments will become essential. Hypertext systems supporting computing devices with environmental sensors will therefore benefit if they can also become context-aware. In this research, we introduce caT (for Context-Aware Trellis), a context-aware hypertext model with associated tools, which supports flexible user (or agent) adaptation to changes in environmental information, such as time, location, bandwidth/cost, etc. The context-aware hypertext model incorporates high-level Petri nets, context-awareness, user-modeling, and fuzzy knowledge handling features into the previously-described Trellis hypertext model. Major features of the high-level Petri net that are explored are its hierarchical net, structured tokens, and flexible net description. Fuzzy knowledge (context) handling is supported by the integration of a fuzzy logic tool into the Petri net. In caT, the author who is accustomed to the caT model and its underlying formalism can specify various dynamic documents using the structured GUI (Graphical User Interface) authoring tool. Afterward, the reader, who does not necessarily need to know the model, can browse the dynamic documents using various browsers, including Web browsers. The browsing behavior of documents specified in the caT model can reflect the reader's contextual (such as location and time) and preference information. To show the usability of caT, we introduce several of its prototype applications that represent various documents such as customized Web documents, formal specifications of software requirements, and cooperative documents. Since caT is based on a formal model, the behavioral characteristics of developed caT models can be analyzed. An analysis tool, which is integrated into the authoring tool, supports the verification of application models. The successful result of the user evaluation showed the potential usability of the model as a context-aware hypertext system. With the increased availability of computing devices equipped with environmental sensors, further research work will enhance the usability of the caT system.