HDM2: Extending the E-R approach to hypermedia application design

The paper is a brief introduction to HDM2, which is the evolution of the Hypertext Design Model HDM [9]. The main features of HDM2, with respect to HDM, are an improvement of the access mechanisms, a generalisation of the notion of link, an extension of the notion of derivation, the definition of hyperviews, and finally a refinement of the definition of browsing semantics. HDM2 (as HDM) is heavily based upon the Entity-Relationship model. There, however, relevant structural differences for Entities and Relationships (webs in our terminology) and access structures. Another important difference is the navigational interpretation of the model, provided by the definition of its browsing semantics.