TY - JOUR T1 - Efficient Web-Based Open and Distance Learning Services JF - Journal of Telematics and Informatics, Elsevier Science, Vol. 17, Issue 3 Y1 - 2000 A1 - Christos Bouras A1 - Apostolos Gkamas A1 - Thrasivoulos Tsiatsos A1 - P Destounis A1 - J Garofalakis A1 - G Sakalis A1 - B Sakopoulos A1 - J Tsaknakis AB - 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 eciently, as required in a web tele-training application, for each type of information maintained, dierent 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 eciently 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) oers 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. ER - TY - CONF T1 - The Performance of Simple Queueing Theoretic Video On Demand Algorithms T2 - APPLIED INFORMATICS (AI 2000), Innsbruck, Austria Y1 - 2000 A1 - Christos Bouras A1 - J Garofalakis A1 - J Tzimas A1 - P Petridis AB - Video On Demand (VOD) Systems comprise an emerging new technology, which is expected to significantly affect everyday life. The implementation of effective commercial VOD systems has to overcome some technical limitations, such as the low bandwidth offered by the existing communication channels. In our work we present some simple queuing theoretic algorithms for the optimal use of a limited number of communication channels keeping a fair policy for the users requests. We compare our algorithms with well-known algorithms, by means of simulation. JF - APPLIED INFORMATICS (AI 2000), Innsbruck, Austria ER - TY - JOUR T1 - A Cooperative Environment for Local Government: An Internet – Intranet Approach JF - Journal of Telematics and Informatics, Elsevier Science, Vol. 16, Issue 1-2 Y1 - 1999 A1 - Christos Bouras A1 - Vasilis Triantafillou A1 - P Destounis A1 - J Garofalakis A1 - J Tzimas A1 - P Zarafidis AB -
In this paper we present a Web-based, database oriented CSCW system to support information dispersal between di€erent Local Government authorities (Region, Prefecture and Municipalities) and the citizens. The system is implemented around the `shared workspace' notion, a group of directories and ®les controlled by the users of the workspace. Intranet and Extranet technologies are exploited to enable asynchronous and synchronous co-operation, manipulation of information from heterogeneous sources, security and easy administration, providing in parallel advanced communication facilities. We propose an innovative approach for the development of shared workspaces over WWW, based on state-of-the-art software platforms, integrating WWW and database technologies. The whole system was developed under a project funded by the Greek General Secretariat of Research and Technology and aims in the ecient distribution and management of information between and within di€erent types of local authorities (Municipalities, Prefectures).
ER - TY - CONF T1 - Cooperative Information Systems over the Internet and the WWW T2 - EUROMEDIA 99-APTEC, Munich, Germany Y1 - 1999 A1 - Christos Bouras A1 - Vasilis Triantafillou A1 - P Destounis A1 - J Garofalakis A1 - J Tzimas A1 - P Zarafidis AB - In this paper we present a WWW-based approach for the development of a system supporting information sharing within an organizational environment. The system developed is exploiting Intranet and Extranet technologies enabling asynchronous and synchronous cooperation, manipulation of information from heterogeneous sources, security and easy administration, providing in parallel advanced communication facilities. We propose an innovative approach for the development of shared workspaces over WWW, based on state-of-the-art software platforms, integrating WWW and database technologies. The whole system was developed under a project funded by the Greek General Secretariat of Research and Technology and aims in the efficient distribution and management of information between and within different types of local authorities (Municipalities, Prefectures). JF - EUROMEDIA 99-APTEC, Munich, Germany ER - TY - CONF T1 - Efficient Data Management to support Educational Activities T2 - Interactive Computer aided Learning-Tools and Applications-ICL 99,Villach, Austria Y1 - 1999 A1 - Christos Bouras A1 - Apostolos Gkamas A1 - Thrasivoulos Tsiatsos A1 - P Destounis A1 - J Garofalakis A1 - G Sakalis A1 - B Sakopoulos A1 - J Tsaknakis AB - 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 efficiently, as required in a Web Tele-training Application, for each type of information maintained different strategies must be deployed according to their behaviourand structure. The diversity and complexity of data, the network aspect of the application and web deficiencies impose an architecture design incorporating a plethora of technologies and tools that must be integrated in such a fashion that they efficiently 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 a open and distance learning system that access the information stored in a database and the file system, their underlying technology, their interaction with the network services, and features regarding the ways they address issues faced in a open vendor-independent distance learning environment and outlines the system’s overall architecture. JF - Interactive Computer aided Learning-Tools and Applications-ICL 99,Villach, Austria ER - TY - JOUR T1 - Analytical Performance Models for Multistage Interconnection Networks with finite, infinite and zero length buffers JF - PERFORMANCE EVALUATION JOURNAL, Elsevier Science, Vol. 34 Y1 - 1998 A1 - Christos Bouras A1 - Paul Spirakis A1 - Vasilis Triantafillou A1 - J Garofalakis AB - Multistage Interconnection Networks (MINs) with crossbar switches have been used to interconnect processors and memory modules in parallel multiprocessor systems. They also play an increasingly important role in the development of ATM networks. In this paper we analyze the general case of MINs, made of kxk switches with finite, infinite or zero length buffers (unbuffered). The exact solution of the steady state distribution of the first stage is derived for all cases. We use this to get an approximation for the steady state distributions in the second stage and beyond. In the case of unbuffered switches we reach the known exact solution for all the stages of the MIN. Our results are validated by extensive simulations. ER - TY - CONF T1 - An Intranet and Internet based Information System for Administration and Information purposes T2 - 4th European Digital Cities Conference: Changing patterns of urban life, Salzburg, Austria Y1 - 1998 A1 - Christos Bouras A1 - Vasilis Triantafillou A1 - P Destounis A1 - J Garofalakis A1 - J Tzimas A1 - P Zarafidis AB - This work presents a system developed within a project funded by the Greek Government. The system deals with the distribution of information and the exchange of documents within, from and towards (region, municipalities, citizens, various groups etc.) the prefecture of Corfu. It is exploiting Intranet and Extranet technologies in order to enable asynchronous and synchronous cooperation, manipulation of information from heterogeneous sources, security and easy administration, providing in parallel advanced communication facilities. JF - 4th European Digital Cities Conference: Changing patterns of urban life, Salzburg, Austria ER - TY - JOUR T1 - Results and experience from the application of a common methodology for Users Requirements Specification in Distance Education using Telematics JF - Journal of Technology and Teacher Education -JTATE, AACE, Vol. 6, Issue 1 Y1 - 1998 A1 - Christos Bouras A1 - Paul Spirakis A1 - P Lampsas A1 - G Tsakarissianos A1 - J Garofalakis A1 - K Antonis A1 - N Kastis A1 - S Kontogiannis AB - The cooperation of the Information and Communications Technologies (ICT) and the Educational communities, is recognised as a necessity that must result in the adaptation and tuning of the education processes in terms of pedagogical methodologies, school infrastructure, human resources development and organisational restructuring, in order to efficiently absorb and utilize technological developments. The ICT community has to realize the significance of the users’ needs, the difficulties of the intervention to an old and traditional process. And the need to view their technology applications not only as a technical exercise. The initial phases of the TRENDS project, which are described in this paper, resulted in an agreed common methodology for carrying out the necessary investigation of the user needs in secondary education. This methodology, which was followed more or less in all participating countries, produced answers to questions concerning the role of the educators and their basic training, their familiarity with technology, education policies from a trans-European perspective, the content, forms and aims of further training, the distance training of teachers in the use of new technologies, the motives, incentives and organisational schemes for enhancing re-education, the needs of the educational environment and technology-based training, the needs of the educators in practical didactic methods, etc. ER - TY - CONF T1 - Conclusions on the Analysis of User Requirements concerning the use of ICT in the Didactic Process T2 - ED-MEDIA/ED-TELECOM 97, Calgary, Canada Y1 - 1997 A1 - Christos Bouras A1 - Paul Spirakis A1 - P Lampsas A1 - G Tsakarissianos A1 - J Garofalakis A1 - K Antonis A1 - N Kastis A1 - S Kontogiannis AB - The co-operation of the Information and Communications Technologies (ICT) and the Educational Society, is deemed necessary for the adaptation and tuning of the didactic process in terms of pedagogical methodologies, school infrastructure, human resources utilisation and organisational restructuring. The use of ICT in the classroom should be viewed as a highly influencing tool that will support the educators’ effort for interaction with their students, rather than as a technical exercise. The initial phases of the TRENDS project, which are described in this paper, resulted in a widely accepted common methodology, that complies with the international standards for determining the User Requirements in the Secondary Education. The major results emerged from this survey are presented here, as well as some common axes that deal with the application of ICT in the didactic process. JF - ED-MEDIA/ED-TELECOM 97, Calgary, Canada ER - TY - CONF T1 - The Design and Development of Advanced Network Services over the Patras University Campus Network T2 - 5th International Conference on Computers in Education-ICCE 97, Sarawak, Malaysia Y1 - 1997 A1 - Christos Bouras A1 - Paul Spirakis A1 - Vasilis Triantafillou A1 - J Garofalakis A1 - J Tsaknakis A1 - J Tzimas A1 - A Tsakalidis A1 - I Antoniou A1 - D Karageorgopoylos A1 - B Basiliadis A1 - P Kappos AB - This paper presents some results of the initial phases of a big internal project running at the University of Patras. In this project - which is co-funded by the European Union - our team is responsible for the development of the Advanced Network Services over the Campus Network, which is being established during the project. In the following chapters we first present the general perspective and the architecture of the integrated system which offers the set of advanced services to the University community. We then describe in detail the different services (WWW and Intranet, On-line teletraining, Computer supported cooperative work, and Off-line teletraining). A key characteristic of the system is the integration of existing commercial tools, with tools that we are developing for the specific needs of the foreseen users. It is evident that this system can be considered as a pilot project for large and demanding user communities, as is the case with the University of Patras. JF - 5th International Conference on Computers in Education-ICCE 97, Sarawak, Malaysia ER - TY - CONF T1 - A General Performance Model for Multistage Interconnection Networks T2 - Euro-Par '97, Passau, Germany Y1 - 1997 A1 - Christos Bouras A1 - Paul Spirakis A1 - Vasilis Triantafillou A1 - J Garofalakis AB - Multistage Interconnection Networks (MINs) with crossbar switches are used to interconnect processors and memory modules in parallel multiprocessor systems. In this paper we analyze the general case of MINs, made of kk switches with nite, innite or zero length buers (unbuered). The exact solution of the steady state distribution of the rst stage is derived for all cases. We use this to get an approximation for the steady state distributions in the second stage and beyond. In the case of unbuered switches we reach the known exact solution for all the stages of the MIN. Our results are validated by extensive simulations. Keywords: analytical models, queueing theory models, evaluation. JF - Euro-Par '97, Passau, Germany ER - TY - CONF T1 - RECPHONE: A new environment for medical remote expert consultation T2 - EuroPACS'91, 9th International Meeting, Berlin, Germany Y1 - 1991 A1 - Christos Bouras A1 - Paul Spirakis A1 - J Garofalakis A1 - G Papoutsopoulos A1 - P Basiroglou JF - EuroPACS'91, 9th International Meeting, Berlin, Germany ER - TY - CONF T1 - Queueing Delays in Buffered Multistage Interconnection Networks T2 - ACM SIGMETRICS Conference 1987, Banff, Alberta, Canada Y1 - 1987 A1 - Christos Bouras A1 - Paul Spirakis A1 - Vasilis Triantafillou A1 - J Garofalakis JF - ACM SIGMETRICS Conference 1987, Banff, Alberta, Canada ER -