A Collection Model for Data Management in Object-Oriented Systems

This thesis addresses the question of how to provide data management services in object-oriented systems with reliable persistent object stores. It proposes an object data model, called the collection model, which serves as a foundation for the construction of such services. The collection model is general in that it is independent of any particular implementation platform. In part, this independence is achieved through the separation of the data model from the underlying type model. There are two components of the collection model - a structural model, BROOM, and an operational model based on an algebra of collections. The structural model is semantically rich and exhibits properties of both the entity-relationship and semantic data models. Hoary collections are used to represent entity categories and binary collections to represent relationships between entities. Classification structures are based on the notion of a. collection family which represents various forms of conceptual dependencies among the collections of a. family. The requirements for supporting the various forms of evolution in object-oriented database systems are presented. An extension to the collection model is proposed to support object evolution whereby objects can migrate within classification structures. Two existing realisations of the collection model are described. One is a. prototype, single-user system implemented in Prolog. The other forms the basis of the Object Data. Management Services of the Comandos platform for distributed, object-oriented applications. A general approach to object data model design, specification and realisation is advocated. In particular, a metacircular description of the collection model is used as an intermediate form of data model specification. This metacircular description is then transformed into a formal specification in the Z language

Design of a shared whiteboard component for multimedia conferencing

This paper reports on the development of a framework for multimedia applications in the domain of tele-education. The paper focuses on the protocol design of a specific component of the framework, namely a shared whiteboard application. The relationship of this component with other components of the framework is also discussed. A salient feature of the framework is that it uses an advanced ATM-based network service. The design of the shared whiteboard component is considered representative for the design as a whole, and is used to illustrate how a flexible protocol architecture utilizing innovative network functions and satisfying demanding user requirements can be developed

Learning from AI : new trends in database technology

Recently some researchers in the areas of database data modelling and knowledge representations in artificial intelligence have recognized that they share many common goals. In this survey paper we show the relationship between database and artificial intelligence research. We show that there has been a tendency for data models to incorporate more modelling techniques developed for knowledge representations in artificial intelligence as the desire to incorporate more application oriented semantics, user friendliness, and flexibility has increased. Increasing the semantics of the representation is the key to capturing the "reality" of the database environment, increasing user friendliness, and facilitating the support of multiple, possibly conflicting, user views of the information contained in a database