Efficient web-based open and distance learning services

In this paper, we present data management issues faced during the design and development of an open distance learning system for the University of Patras, Greece. In order to handle data eciently, as required in a web tele-training application, for each type of information maintained, di€erent strategies must be deployed according to their behaviour and structure. The diversity and complexity of data, the network aspect of the application and web de®ciencies impose an architecture design incorporating a plethora of technologies and tools that must be integrated in such a fashion that they eciently organise these data preserving their relationships. This presents a software engineering challenge requiring coherence of solutions at all levels: structures, consistency, security, models, and protocols. The paper presents the data components of an open and distance learning (ODL) system that access the information stored in a database and the ®le system, their underlying technology, their interaction with the network services, and features regarding the ways they address issues faced in an open vendorindependent distance learning environment and outlines the system's overall architecture. In addition, this paper presents the architecture, the design and the services of a network-based information system that supports open and distance learning activities. The open and distance learning information system (ODLIS) o€ers synchronous and asynchronous distance learning and management of information system (MIS) services to support the educational procedure. The ODLIS is a web-based application, which runs over the Internet using real time protocols. Ó 2000 Elsevier Science Ltd. All rights reserved.