A methodology for design of large hypermedia systems

Hypermedia is a young medium and design methods for hypermedia systems are in a relatively early stage of development. Current design methods have followed one of three different paths. They are Scripting, based on simplified programming languages that allow definition of the content and sequence of the system; interactive tools which allow the system to be constructed by form filling and `programming by example´ and database methods which treat the system as a database of visual information. This paper proposes a new method for the design of very large, highly interactive, hypermedia databases for which correctness and reliability is a major requirement. Examples of such databases are the technical documentation systems for safety critical systems. When applied to systems of this type existing methods show severe shortcomings, the interactive and scripting methods because they cannot guarantee correctness or reliability and the database methods because they cannot guarantee the required interactive properties. The new method is based on one of the most successful methodologies for the rigorous design of real time systems software, the formal description of the system using process algebras. Real time systems share many basic characteristics with interactive systems and the application of their design methods allows systems to be rigorously designed both with respect to their content and their interactive behaviour. Furthermore, the use of these methods offers the prospect of the formal verification of the operational characteristics of these systems if not the correctness of their content. It is argued that a design method based on process algebras possesses the necessary properties for large, safety critical documentation systems and also that if correctly structured such a method should be accessible to hypermedia designers