The Notion of Active Object - Oriented

Open Hypermedia Systems (OHS) are characterized by distributed, heterogeneous pieces of information. To cope with the main challenges of OHS one has to tackle consistency, eeciency, and interoperability issues. In this position paper we propose an OHS architecture based on an active object-oriented database system as well as SGML/HyTime as standardized interchange formats. By using active object-oriented database systems consistency, and eeciency in data representation is ensured. By using international standards interoperability of hypermedia information systems is reached. Open Hypermedia Systems (OHS) incorporate one of the basic ideas of hypermedia technology, i.e., to interconnect diierent sources of information. Thus two main issues to be addressed can be identiied in the literature 17]; namely reference models and frameworks as basic architectures, and standards for hypermedia exchange. Hypertext reference models and frameworks address the issue of open hyper-media systems by providing generic frameworks that ensureing the idea of in-teroperability. These frameworks allow the integration of diierent hypermedia systems by exible, multi-layered architectures. There exist several approaches for refernce models and frameworks of hypermedia systems. For an overview see e.g. 4, 17]. In comparison to models and frameworks, standards for hypermedia interchange have a somehow diierent objective in achieving interoperability. Their main goal is to deene agreed structures and formats for hypermedia information in order 1 to allow the interchange between diierent systems. Additionally, as technology develops { for example, in the move to all-digital media { everyone must keep abreast of rapidly changing production methods and quality standards. However, in spite of the bewildering array of multimedia formats, and the skills demanded to employ them, we consider SGML (Standard Generalized Markup Language 11]) and HyTime (Hypermedia/Time-based Structuring Language 12]) as most essential due to their generic and fundamental nature. Based on experience with existing refernce models and frameworks as well as hy-permedia standards we introduce an architectural framework based on active object-oriented database systems and SGML/HyTime to cope with consistency, eeciency, and interoperability issues. So far, hypermedia systems have been mainly built based on relational database technology , e.g. 15]. The more exible and expressive object-oriented model, however, seems more appropriate for hypermedia 4, 5] due to the intuitive and thus more ee-cient data representation in terms of objects. In addition, hypermedia systems require scheduling and constraint management. Traditional database systems { including (standard) object-oriented systems { cannot adequately cope with these requirements. The main reason being that a polling strategy is …