Internet users have become well acquainted with the World Wide Web (WWW) system, and WWW has become the most significant service on the Internet. In the near future, the importance of large scale hypermedia database systems based on WWW technologies is expected to continue to increace. The present study focuses on the issue of managing hyperlink integrity constraints on WWW like hypermedia database systems. After formally defining path existence constraint definitions(PEDs) using intuitive examples, we apply the notion of PEDs to represent hyperlink integrity constraints. Intuitively, a PED can be used to represent the following integrity constraint. If a reference path exists in a given database, then another corresponding reference path must also exist. An outline of a prototype hypermedia database system, AYATORI, which is based on the proposed model and under development, is also mentioned.

This paper presents the design concept of the MEMORI, MHEG Engine for Multimedia information Object Retrieval and Interchange, which consists of three functional modules; the decoder, the object manager, and interpreter. Based on our modular design, the MEMORI has been implemented on the UNIX workstation. The menu-driven object generator has also been developed to generate the test objects conforming to the MHEG. Using the object generator, several multimedia/hypermedia test objects have been composed on the basis of presentation scenarios. The results show that the MEMORI correctly decodes, manages, and interprets the MHEG objects. The MEMORI can be utilized for the interactive multimedia server as well as the multimedia presentation system.

In order to make the hyperling generation mechanism not only dynamic but also systematic, we will mainly describe the use of the querying and abstraction facilities in hypertext database systems. Our work focuses on a dynamic, abstract and systematic link generation mechanism. The prototype system named TextLink/Gem is implemented by taking an object-oriented approach, and the notions of anchor objects, query-pair links, polymorphic links and inheritable links, on which the system is based, and their implementations are described in detail.