Extensibility in component-based open hypermedia systems

Extensibility has long been recognized as a highly desirable trait of hypermedia systems. Furthermore, many hypermedia systems claim to provide some form of extensibility. However, consensus on what functionality of a hypermedia should be extensible, how this extensibility should be presented to extension implementers, and even a rigorous definition of the term itself have evaded the hypermedia field. In this paper, we start by offering one possible definition of extensibility. Then, we describe the extensibility mechanisms provided in the HOSS hypermedia system, and analyse these mechanisms in light of our proposed definition. We point out some of the aspects of the design and implementation of the HOSS extensibility mechanism that caused problems for extension developers. We then consider the extensibility mechanisms of Construct, the codebase successor to HOSS and a number of other hypermedia systems, focusing on how the analysis of the HOSS mechanisms affected analogous mechanisms in Construct. We conclude with a reflection upon our proposed definition of extensibility in hypermedia systems.