Specification and Efficient Monitoring of Local Graph-based Constraints in Hypermedia Systems

The concept of hypermedia has existed for about fifty years. It became a practical technology in the seventies, and widely available in the eighties. The concept has proven quite useful as a paradigm for information presentation, and been applied to information relevant to many diverse fields. However, the networks of semantic connections that exist in hypermedia systems are often so large and complex that they become overwhelming to people trying to find information in them. This paper presents a number of types of constraints representing application semantics as a way of reducing the complexity of networks of semantic connections in hypermedia. Unlike constraints developed in the past, those presented in this work are graph-based and can be evaluated within local regions of the hypermedia system. In addition, this work presents an algebra on overview graphs of hypermedia systems. To formalize the definitions of the algebra and constraints, this paper presents a data model for hypermedia. Also, this paper presents an algebra on networks of semantic connections in hypermedia. This algebra, in itself, can be used to define overview graphs on networks of semantic connections. In addition, the algebra increases the expressive power of the constraints by allowing the definition of overview graphs to which the constraints can be applied