Object-Oriented Modeling for Hypermedia Systems Using the VODAK Model Language

Abstract

More and more documents become available in electronic form, e.g., in the publishing sector, product design and specification, documentation, medical records, etc. Real applications in industry have a serious problem of handling masses of documents. Therefore, there is a growing demand of database support in the areas of document modelling, in particular hypermedia document modelling, i.e. documents containing multimedia data. As documents represent intrinsically complex structured data object-oriented database management (OODBMS) technology with its ability to handle such kind of information offers itself as a very promising way to tackle this problem as opposed to conventional database technology which was designed to handle simple structured data. OODBMS technology, although fairly developed today, needs to be extended and adapted to meet the specific requirements of hypermedia document modelling. Within the VODAK project at GMD-IPSI we developed an open OODBMS. Its data model VML can be tailored to the needs of particular applications. In this paper we first present the key principles and main features of the open object-oriented data model VML which can be extended at the meta level. This includes utilizing the concept of metaclasses. By this, system administrators may tailor the kernel data model to the requirements of specific applications and introduce, for example, additional types of links as they can be found in hypertext models at the data-model level. Second we illustrate how this open object-oriented data model can be tailored to the needs of modelling hypermedia documents as they are used in the framework of, e.g., collaborative authoring environments. We incrementally develop a model for hypermedia documents, discuss the advantages and disadvantages as well as the various alternatives.