00544nam a2200121 4500008004100000245009200041210006900133100002100202700002300223700001900246700002400265856013300289 2008 eng d00aDiscrete Mathematics: A) The Mathematics of Computer Science, B) Problems and Solutions0 aDiscrete Mathematics A The Mathematics of Computer Science B Pro1 aBouras, Christos1 aKirousis, Lefteris1 aSpirakis, Paul1 aVoutsadakis, George uhttps://telematics.upatras.gr/telematics/publications/discrete-mathematics-mathematics-computer-science-b-problems-and-solutions01480nas a2200145 4500008004100000245006200041210006200103300001600165520096300181100002101144700002301165700001901188700001601207856011101223 2003 eng d00aCompetitive Video on Demand Schedulers for Popular Movies0 aCompetitive Video on Demand Schedulers for Popular Movies aPP. 49 - 613 a

In this paper we investigate the online video on demand problem, namely having to accept or reject a request for a movie without knowing the future requests. We present online movie-scheduling schemes that implement the principles of refusal by choice and delayed noti- 4cation. A novel way to schedule movies that exploits the knowledge of the distribution of the preference of requests for movies, is shown to have a competitive ratio that outperforms all the previously knownschemes inpractical situations. Infact, our scheduler has a competitive ratio bounded above by a constant, independent of the number of the users, channels, or movies, in the case that a large fraction of the requests tends to concentrate in a small number of movies. We extend our approach by presenting an “adaptive” randomized scheduler which initially is not aware of the movie popularities but it adapts to it, and achieves the same asymptotic competitive ratio.

1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aPantziou, G uhttps://telematics.upatras.gr/telematics/publications/competitive-video-demand-schedulers-popular-movies-001497nas a2200157 4500008004100000245008000041210006900121300001200190520091700202100002101119700002301140700001901163700001401182700001601196856012701212 2002 eng d00aAn Architecture for Interactive Distributed Multimedia Information Services0 aArchitecture for Interactive Distributed Multimedia Information  a 3 - 103 aIn this work, we present an architecture for interactive distributed multimedia information services. The service consists of three basic parts, the clients, the access servers, and the content servers. Clients manage the presentation of the requested multimedia documents, while also ensure the synchronization among various involved media. Special policies for the synchronized presentation of multimedia documents and user interactions management are discussed. Access servers authorize the users for legitimate use of the service, while also provide various searching capabilities Content servers manage the transportation of multimedia documents over a broadband network and the user interactions. The proposed architecture preserves scalability, flexibility and modularity due to the distributed nature of the architecture, while also results in good performance due to the dynamic allocation of resources.1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aMoiras, D1 aOuzounis, V uhttps://telematics.upatras.gr/telematics/publications/architecture-interactive-distributed-multimedia-information-services01488nas a2200145 4500008004100000245009600041210006900137260001000206300001500216520091000231100002101141700001901162700001501181856014601196 2002 eng d00aSTEPS: Supporting Traditional Education ProcedureS-A TCP/IP Multimedia Networks-Based Model0 aSTEPS Supporting Traditional Education ProcedureSA TCPIP Multime cMarch a 251 - 2763 aThis paper describes an integrated model for the realization of an Open and Distance Learning (ODL) environment supporting traditional learning procedures, through collaborative learning and active participation of the involved group of students. Internet technologies are used as a vehicle for distribution of interactive multimedia at the user’s desktop. We also present off-the-shelf solutions for the architecture and implementation of an Educational Network necessary to support the ODL environment. An Educational Entity (specially shaped part of a legal educational authority) is also prescribed as the central point for the Educational Network, being the content provider and the learning procedure evaluator. It is mainly intended to be used in a higher education setting, aspiring to be an efficient solution for the common educational needs of a group of students and teachers or researchers.1 aBouras, Christos1 aSpirakis, Paul1 aLampsas, P uhttps://telematics.upatras.gr/telematics/publications/steps-supporting-traditional-education-procedures-tcpip-multimedia-networks-based-model01669nas a2200145 4500008004100000245007700041210006900118260002000187300001500207520112900222100002101351700001901372700001401391856011801405 2000 eng d00aAn efficient algorithm to improve handoff in mobility for IP v6 protocol0 aefficient algorithm to improve handoff in mobility for IP v6 pro c11 - 14 October a 505 - 5113 aThis paper describes an extension of the mobility support for the IPv6 protocol, which is currently an Internet Draft. We argue that by processing geographical data information a mobile node can efficiently switch between different LANs without disturbance to ongoing data sessions. Furthermore the number of location update messages diminishes as the mobile node transmits them only when switching to a new LAN. This extension requires that each router of the foreign networks the mobile node visits, advertises the GPS coordinates of x points that describe its region. It also requires that the mobile node is capable of receiving GPS signals. Once having collected this information the mobile node can safely figure whether it will continue to be served by the same LAN or it has to switch to a different one because soon it will be out of the old LAN’s range. Furthermore using this information the mobile node can also decide to which LAN it is preferable to switch. Lower-layer information, when it is available, such as signal strength or signal quality can be used as auxiliary indications for the switch decision.1 aBouras, Christos1 aSpirakis, Paul1 aSiahos, Y uhttps://telematics.upatras.gr/telematics/publications/efficient-algorithm-improve-handoff-mobility-ip-v6-protocol00467nam a2200121 4500008004100000245005900041210005700100100002100157700002300178700001900201700001700220856010800237 1999 eng d00aIntroduction to graphs: Theory, problems and solutions0 aIntroduction to graphs Theory problems and solutions1 aBouras, Christos1 aKirousis, Lefteris1 aSpirakis, Paul1 aStamatiou, G uhttps://telematics.upatras.gr/telematics/publications/introduction-graphs-theory-problems-and-solutions01294nas a2200169 4500008004100000245009300041210006900134300001500203520065900218100002100877700002300898700001900921700001400940700001600954700001500970856013900985 1999 eng d00aOn-Demand Hypermedia/Mutimedia Service using Pre-Orcestrated Scenarios over the Internet0 aOnDemand HypermediaMutimedia Service using PreOrcestrated Scenar a 741 - 7623 aIn this paper we present a unified approach for delivering hypermedia/multimedia objects over broadband networks. The described service consists of several multimedia servers and a set of functions that intend to present to the end user interactive information in real-time. The hypermedia documents are structured using a hypermedia markup language that keeps information of the spatiotemporal relationships among document’s media components. In order to deal with the variant network behavior, buffering manipulation mechanisms and grading of the transmitted media quality techniques are proposed to smooth presentation and synchronization anomalies.1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aMoiras, D1 aOuzounis, V1 aTatakis, A uhttps://telematics.upatras.gr/telematics/publications/demand-hypermediamutimedia-service-using-pre-orcestrated-scenarios-over-internet01353nas a2200145 4500008004100000245012000041210006900161300001500230520073200245100002100977700001900998700002701017700001901044856014401063 1998 eng d00aAnalytical Performance Models for Multistage Interconnection Networks with finite, infinite and zero length buffers0 aAnalytical Performance Models for Multistage Interconnection Net a 169 - 1823 aMultistage 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.1 aBouras, Christos1 aSpirakis, Paul1 aTriantafillou, Vasilis1 aGarofalakis, J uhttps://telematics.upatras.gr/telematics/publications/analytical-performance-models-multistage-interconnection-networks-finite-infinite-and00905nas a2200145 4500008004100000245007300041210006900114260002100183300001500204520036300219100002100582700001900603700001600622856012100638 1998 eng d00aOn Demand Delivery of Multimedia Documents using Distributed Objects0 aDemand Delivery of Multimedia Documents using Distributed Object c14 - 16 December a 357 - 3603 aIn this paper, we propose an architecture for the ondemand delivery of multimedia documents over broadband networks using distributed objects. The basic components of our model are the network agents and the presentation agents. Our model preserves flexibility, transparency and modularity and value added opportunity due to the usage of distributed objects.1 aBouras, Christos1 aSpirakis, Paul1 aOuzounis, V uhttps://telematics.upatras.gr/telematics/publications/demand-delivery-multimedia-documents-using-distributed-objects01182nas a2200169 4500008004100000245010000041210006900141260001100210520054100221100002100762700002300783700001900806700001400825700001600839700001500855856014200870 1998 eng d00aImplementing spatio-temporal relations for hypermedia presentations using an HTML-like language0 aImplementing spatiotemporal relations for hypermedia presentatio c13 May3 aHypermedia is currently the trend in delivering information composed of various forms of media. Up to now most systems lack the ability to present the user with hypermedia information containing various media that have specific spatio-temporal relations. In this paper we propose and describe a model that can describe such kinds of hypermedia presentations. The core of the model is an HTML-like language that supports tags for the description of timing relations between the information objects that compose a hypermedia presentation.1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aMoiras, D1 aOuzounis, V1 aTatakis, A uhttps://telematics.upatras.gr/telematics/publications/implementing-spatio-temporal-relations-hypermedia-presentations-using-html-language01409nas a2200181 4500008004100000245007300041210006900114260002000183300001500203520075500218100001900973700001900992700002701011700002901038700001501067700001801082856012701100 1998 eng d00aMRP II-based Production Management Using Intelligent Decision Making0 aMRP IIbased Production Management Using Intelligent Decision Mak bSpringer Verlag a 379 - 4123 a

This paper presents an extended MRP II-based production management system (PMS), which improves the traditional MRP II paradigm by attaching an intelligent decision supporting system (IDSS) to it. The IDSS is attached to the lowest level of the PMS, namely the production activity control (PAC) subsystem, and includes a simulator, that imitates real system behaviour, a knowledge-based component, that imitates expert reasoning, and a real-time database manager, that acts as the data pool and the communication gate between them. The IDSS is capable of performing off-line and on-line rescheduling, thus resulting in more realistic short-term plans. Analysis of the related case problem and implementation of the system are also discussed.

1 aSofotassios, D1 aSpirakis, Paul1 aTriantafillou, Vasilis1 aHatzilygeroudis, Ioannis1 aDendris, N1 aTsakalidis, A uhttps://telematics.upatras.gr/telematics/publications/mrp-ii-based-production-management-using-intelligent-decision-making01557nas a2200181 4500008004100000245008300041210006900124260001700193300001500210520091300225100002101138700001901159700001501178700001701193700001501210700001301225856013701238 1998 eng d00aMultimedia Architecture offering Open Distance Learning Services over Internet0 aMultimedia Architecture offering Open Distance Learning Services c22 - 25 June a 145 - 1493 aThe increase in the use of the Internet not only as a repository of resources for learning but also as a means for the delivery of courses and specially prepared teaching material is a particularly significant innovation in the range of education. The main concept here is a Virtual class, which is based on the principles of CSCL (Computer Supported Collaborative Learning) systems. This paper describes an integrated, WWW based platform for the development of web enabled environments over TCP/IP networks, such as Internet. This platform is designated through a Teletraining and Collaborative Learning Application. The proposed platform aspires to be an efficient solution for a group of students and teachers that need a shared workspace, supporting remote interactive lectures, flexible exchange of teaching material and various communication utilities, with focus on transparent and secure interaction.1 aBouras, Christos1 aSpirakis, Paul1 aLampsas, P1 aZarafidis, P1 aBazaios, A1 aZoura, A uhttps://telematics.upatras.gr/telematics/publications/multimedia-architecture-offering-open-distance-learning-services-over-internet02190nas a2200193 4500008004100000245014800041210006900189300001300258520143500271100002101706700001901727700001501746700002201761700001901783700001501802700001401817700002001831856014501851 1998 eng d00aResults and experience from the application of a common methodology for Users Requirements Specification in Distance Education using Telematics0 aResults and experience from the application of a common methodol a 61 - 743 aThe 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.1 aBouras, Christos1 aSpirakis, Paul1 aLampsas, P1 aTsakarissianos, G1 aGarofalakis, J1 aAntonis, K1 aKastis, N1 aKontogiannis, S uhttps://telematics.upatras.gr/telematics/publications/results-and-experience-application-common-methodology-users-requirements-specification01275nas a2200145 4500008004100000245011800041210006900159260001800228300001500246520066700261100002100928700001900949700001500968856014600983 1998 eng d00aTraining Centres: An Architecture for the Realisation of Open and Distance Learning Environments using Telematics0 aTraining Centres An Architecture for the Realisation of Open and c10 - 14 March a 118 - 1203 aIn this paper, we are describing an architecture for the realisation of Open and Distance Learning (ODL) Environments using Telematics. The approach of using Training Centres as dedicated education services providers, located at the premises of an educational authority is discussed. These Training Centres may be Points of Presence of an international educational network (as is the case in the TRENDS Project in the context of which Training Centres were studied). Crucial aspects of the feasibility study, aiming to investigate the operational and organisational conditions of the Centres, that must precede the implementation of a Training Centre, are cited.1 aBouras, Christos1 aSpirakis, Paul1 aLampsas, P uhttps://telematics.upatras.gr/telematics/publications/training-centres-architecture-realisation-open-and-distance-learning-environments-using01477nas a2200145 4500008004100000245006200041210006200103260001700165520096100182100002101143700002301164700001901187700001601206856010901222 1997 eng d00aCompetitive Video on Demand Schedulers for Popular Movies0 aCompetitive Video on Demand Schedulers for Popular Movies c11 - 12 July3 a

In this paper we investigate the online video on demand problem, namely having to accept or reject a request for a movie without knowing the future requests. We present online movie-scheduling schemes that implement the principles of refusal by choice and delayed noti cation. A novel way to schedule movies that exploits the knowledge of the distribution of the preference of requests for movies, is shown to have a competitive ratio that outperforms all the previously known schemes in practical situations. In fact, our scheduler has a competitive ratio bounded above by a constant, independent of the number of the users, channels, or movies, in the case that a large fraction of the requests tends to concentrate in a small number of movies. We extend our approach by presenting an \adaptive" randomized scheduler which initially is not aware of the movie popularities but it adapts to it, and achieves a similar asymptotic competitive ratio.

1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aPantziou, G uhttps://telematics.upatras.gr/telematics/publications/competitive-video-demand-schedulers-popular-movies01620nas a2200205 4500008004100000245010300041210006900144260001700213300001300230520089300243100002101136700001901157700001501176700002201191700001901213700001501232700001401247700002001261856013301281 1997 eng d00aConclusions on the Analysis of User Requirements concerning the use of ICT in the Didactic Process0 aConclusions on the Analysis of User Requirements concerning the  c14 - 19 June a 13 - 183 aThe 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.1 aBouras, Christos1 aSpirakis, Paul1 aLampsas, P1 aTsakarissianos, G1 aGarofalakis, J1 aAntonis, K1 aKastis, N1 aKontogiannis, S uhttps://telematics.upatras.gr/telematics/publications/conclusions-analysis-user-requirements-concerning-use-ict-didactic-process01832nas a2200241 4500008004100000245010200041210006900143260001900212300001500231520099200246100002101238700001901259700002701278700001901305700001701324700001401341700001801355700001601373700002401389700001801413700001401431856014501445 1997 eng d00aThe Design and Development of Advanced Network Services over the Patras University Campus Network0 aDesign and Development of Advanced Network Services over the Pat c2 - 6 December a 420 - 4273 aThis 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.1 aBouras, Christos1 aSpirakis, Paul1 aTriantafillou, Vasilis1 aGarofalakis, J1 aTsaknakis, J1 aTzimas, J1 aTsakalidis, A1 aAntoniou, I1 aKarageorgopoylos, D1 aBasiliadis, B1 aKappos, P uhttps://telematics.upatras.gr/telematics/publications/design-and-development-advanced-network-services-over-patras-university-campus-network01230nas a2200145 4500008004100000245005600041210005600097260002800153520072600181100002100907700001900928700001500947700001600962856010600978 1997 eng d00aEnabling Distance Education over the World Wide Web0 aEnabling Distance Education over the World Wide Web c31 Octiber - 5 November3 aThe recent advancements in the field of the information and communication technology resulted in a revolution comparable to the industrial revolution. The basis of this revolution is the information and the value it has as the pure expression of human knowledge. The technological advancements offer us the ability to process, store, retrieve and transmit information in multiple formats (text, sound, image, video) independently of time, volume and distance. In this paper we present the technology that is required and an architecture for the realization of distance education over the World Wide Web. We also address some basic aspects of the users’ needs that every software tool for distance education should meet.1 aBouras, Christos1 aSpirakis, Paul1 aLampsas, P1 aAntoniou, I uhttps://telematics.upatras.gr/telematics/publications/enabling-distance-education-over-world-wide-web01284nas a2200157 4500008004100000245007200041210006900113260001900182300001600201520070300217100002100920700001900941700002700960700001900987856012001006 1997 eng d00aA General Performance Model for Multistage Interconnection Networks0 aGeneral Performance Model for Multistage Interconnection Network c25 - 29 August a 993 - 10003 aMultistage 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, in nite or zero length bu ers (unbu ered). 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 unbu ered 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.1 aBouras, Christos1 aSpirakis, Paul1 aTriantafillou, Vasilis1 aGarofalakis, J uhttps://telematics.upatras.gr/telematics/publications/general-performance-model-multistage-interconnection-networks01548nas a2200193 4500008004100000245007400041210006900115260001600184300001300200520088400213100002101097700002301118700001901141700001401160700001601174700001601190700002401206856012401230 1997 eng d00aHermes Service: Distributed Hypermedia Educational Services on Demand0 aHermes Service Distributed Hypermedia Educational Services on De c14 - 19 Jne a 19 - 243 aIn this paper we present a distributed HypERMEdia SERVICE (HERMES SERVICE) which supports integrated capabilities for distance education and learning purposes. Hermes service consists of hermes servers and hermes browsers. The users are connected with the service using hermes browsers and retrieve hypermedia lessons organised in thematical units. The lessons are stored in various distributed Hermes servers which retrieve the requested lesson and transmit it to the corresponding browser on on-demand basis. The requested lesson is presented to the user according to a well defined presentation scenario. The media objects are rendered in a synchronized manner according to the spatio-temporal relationships existing among them. Finally, special monitoring mechanism controls the state of the network and adjusts the presentation process so as to improve presentation quality.1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aMoiras, D1 aOuzounis, V1 aAntoniou, I1 aKarageorgopoylos, D uhttps://telematics.upatras.gr/telematics/publications/hermes-service-distributed-hypermedia-educational-services-demand00538nas a2200133 4500008004100000245007800041210006900119260001700188100002100205700002300226700001900249700001500268856012100283 1997 eng d00aAn HTML like language supporting time-depended transmission of hypermedia0 aHTML like language supporting timedepended transmission of hyper c6 - 11 April1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aTatakis, A uhttps://telematics.upatras.gr/telematics/publications/html-language-supporting-time-depended-transmission-hypermedia01060nas a2200169 4500008004100000245006100041210005900102260001700161300001300178520050300191100002100694700001900715700001400734700001600748700001600764856011000780 1997 eng d00aHY-MOST: HYpermedia MOdel for Synchronised presenTations0 aHYMOST HYpermedia MOdel for Synchronised presenTations c6 - 11 April a 18 - 233 aA brief abstract. In this paper we present a new model for hypermedia presentations. This model is based on an HTML-like language which provides the necessary modules for the intermedia synchronisation of the inline media that comprise the hypermedia document. The model also enables a distributed approach in the storage of the hypermedia documents. Additionally, it is capable of incorporating the necessary protocols needed for the real-time delivery of continuous media such as audio and video.1 aBouras, Christos1 aSpirakis, Paul1 aMoiras, D1 aOuzounis, V1 aAntoniou, I uhttps://telematics.upatras.gr/telematics/publications/hy-most-hypermedia-model-synchronised-presentations00565nas a2200133 4500008004100000245009400041210006900135260001600204300001500220100002100235700001900256700001500275856014100290 1997 eng d00aIn-Service Training through ODL Environments:From User Needs To Functional Specifications0 aInService Training through ODL EnvironmentsFrom User Needs To Fu c1 - 5 April a 519 - 5221 aBouras, Christos1 aSpirakis, Paul1 aLampsas, P uhttps://telematics.upatras.gr/telematics/publications/service-training-through-odl-environmentsfrom-user-needs-functional-specifications01155nas a2200157 4500008004100000245006800041210006700109260001900176520059800195100002100793700001900814700001800833700001500851700001800866856011300884 1997 eng d00aODYSSEAS: The Greek Educational Network for Secondary Education0 aODYSSEAS The Greek Educational Network for Secondary Education c5 - 7 November3 aThe purpose of this paper is the description of the project ODYSSEAS. The aim of the project is the design, development, and pilot operation of an integrated network of schools in secondary education in the Greek areas of Achaia, Thrace and Aegean Islands. A special network infrastructure will be created and network software and services (containing a WWW server, network software for teaching the Greek language, applications of administrative support and so on) will be developed. Training of the teachers and pupils and evaluation of the project results will be the final project actions.1 aBouras, Christos1 aSpirakis, Paul1 aHatzilakos, A1 aKoutlis, M1 aPanopoulos, N uhttps://telematics.upatras.gr/telematics/publications/odysseas-greek-educational-network-secondary-education01145nas a2200121 4500008004100000245007600041210006900117300001500186520065800201100001900859700002700878856011800905 1997 eng d00aPure greedy Hot-Potato routing in the 2-d mesh with random destinations0 aPure greedy HotPotato routing in the 2d mesh with random destina a 249 - 2583 aWe analyze here a pure greedy hot-potato routing strategy on a two-dimensional mesh of n^2 nodes. We specifically study the case of n^ 2 packets, originating one per node, to be delivered at random uniform destinations. Each packet attempts to follow the shortest path leading first to the destination row/column (whichever is closest) and then to the actual destination node. A de ection policy is adopted to solve con icts. We prove that all packets are delivered to the destinations in average time O(nlogn). The average is taken over all possible destination functions. No average case analysis of pure greedy hot-potato routing was known up to now.1 aSpirakis, Paul1 aTriantafillou, Vasilis uhttps://telematics.upatras.gr/telematics/publications/pure-greedy-hot-potato-routing-2-d-mesh-random-destinations01701nas a2200145 4500008004100000245004900041210004900090260001700139300001300156520123200169100002101401700001901422700001501441856009901456 1997 eng d00aSuperhighways for Open and Distance Learning0 aSuperhighways for Open and Distance Learning c23 - 25 June a 32 - 363 aAn educational information network, is a multimedia network with a centralized architecture for the provision of educational services. The educational services comprise basic network applications (such as multimedia e-mail, fora for debates on educational subjects, access to already existing information), video distribution of multimedia lessons and a custom developed teletraining tool for the conduction of lessons over a broadband networking infrastructure. The suitability of the widely available broadband networking technologies (ATM, ISDN), as opposed to the alternative of using already existing networking infrastructure (Internet, CATV), for the implementation of educational networks for the realization of an Open and Distance Learning Environment will be examined. More specifically the types of educational services that can be best hosted by each technology and the costs as opposed to the maturity for the deployment of each networking technology will be cited. Finally, a proposal for an implementation scheme of an educational information network, concerning the appropriate (and cost effective) networking infrastructure that can best accommodate the aforementioned educational services will be elaborated.1 aBouras, Christos1 aSpirakis, Paul1 aLampsas, P uhttps://telematics.upatras.gr/telematics/publications/superhighways-open-and-distance-learning01871nas a2200193 4500008004100000245008800041210006900129260001100198300001300209520119000222100002101412700002301433700001901456700001501475700001501490700002001505700001501525856013701540 1997 eng d00aUsing Multimedia/Hypermedia Tools over Networks for Distance Education and Training0 aUsing MultimediaHypermedia Tools over Networks for Distance Educ cSummer a 20 - 263 aThe rapid developments in the Information Technology sector as well as the deployment of faster networks brings us to the era of the New Information Technology (NIT). The citizen of the near future must be able to use them else he will be seriously handicapped in his everyday life. Thus NIT becomes part of the educational process while on the other hand offers the tools and the infrastructure for the establishment of the distance education process. The educators are one of the first professions that must learn to use NIT and its tools. Multimedia/hypermedia tools offer solutions to the problems posed by the distance education process. They can be user-friendly and enticing and they can cover most, if not all, the needs of their users. A lot of prototype systems (tools) for distance education have been developed, each offering a number of functions that aid the process of distance education. The rapid growth of World Wide Web is adding another factor that can lead to the wider deployment of distance education systems. Although the value of distance education is unquestionable there is still a lot of work to be done before a wide spread implementation platform emerges.1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aLampsas, P1 aTatakis, A1 aKontogiannis, S1 aFotakis, D uhttps://telematics.upatras.gr/telematics/publications/using-multimediahypermedia-tools-over-networks-distance-education-and-training00733nas a2200205 4500008004100000245008700041210006900128260001700197300001300214100002100227700002300248700001900271700001500290700001500305700001700320700001600337700001900353700002400372856013100396 1996 eng d00aFINE:Implementation of a Distributed Telematics Environment for Clinical Engineers0 aFINEImplementation of a Distributed Telematics Environment for C c10 -12 April a 56 - 601 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aTatakis, A1 aFotakis, D1 aBalaouras, P1 aChadelis, L1 aPalikarakis, N1 aSandalatzopoulos, R uhttps://telematics.upatras.gr/telematics/publications/fineimplementation-distributed-telematics-environment-clinical-engineers01365nas a2200205 4500008004100000245007900041210007500120260001700195300001300212520061800225100002100843700002300864700001900887700001500906700001500921700002000936700001500956700001600971856017200987 1996 eng d00aAn Interactive Cooperative Teleworking Environment-Tηλεµάθεια ∗0 aInteractive Cooperative Teleworking EnvironmentTηλεµάθεια ∗ c17 - 22 June a 37 - 423 a

In this paper we present the design and the implementation of an interactive environment for cooperative teleworking. Telemathea offers tools that support the communication and the teleworking between tutor and trainee, who may reside in remote geographical regions. This environment offers audio communication over the network as well as support for joint editing of text documents and still images. It supports different audio coding techniques so as to adjust to the available bandwidth, and makes use of the RTP protocol in order to facilitate the exchange of audio and, in the future, video packets.

1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aLampsas, P1 aTatakis, A1 aKontogiannis, S1 aFotakis, D1 aKyriakou, K uhttps://telematics.upatras.gr/telematics/publications/interactive-cooperative-teleworking-environment-t%CE%B7%CE%BB%CE%B5%C2%B5%CE%AC%CE%B8%CE%B5%CE%B9%CE%B1-%E2%88%9701626nas a2200181 4500008004100000245006800041210006600109260001800175300001500193520101000208100002101218700002301239700001901262700001401281700001601295700001501311856011801326 1996 eng d00aOn-Demand Hypermedia/Multimedia Service over Broadband Networks0 aOnDemand HypermediaMultimedia Service over Broadband Networks c6 - 9 August a 224 - 2313 aIn this paper we present a uni ed approach for de- livering hypermedia/multimedia objects over broadband networks. Documents are stored in various multimedia servers, while the inline data may reside in their own media servers, attached to the multimedia servers. The described service consists of several multimedia servers and a set of functions that intend to present to the end user interactive information in real-time. Users interact with the service requesting multimedia docu- ments on demand. Various media streams are trans- mitted over di erent parallel connections according to their transmission requirements. The hypermedia doc- uments are structured using a hypermedia markup lan- guage that keeps information of the spatiotemporal re- lationships among document's media components. In order to deal with the variant network behavior, bu ering manipulation mechanisms and grading of the transmitted media quality techniques are proposed to smooth presentation and synchronization anomalies.1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aMoiras, D1 aOuzounis, V1 aTatakis, A uhttps://telematics.upatras.gr/telematics/publications/demand-hypermediamultimedia-service-over-broadband-networks01595nas a2200133 4500008004100000245008900041210006900130260001000199300001500209520105800224100002101282700001901303856013901322 1996 eng d00aPerformance Modeling of Distributed Timestamp Ordering: Perfect and Imperfect Clocks0 aPerformance Modeling of Distributed Timestamp Ordering Perfect a cApril a 105 - 1303 aThis work presents a model of a distributed database system which provides the framework to study the performance of timestamp ordering concurrency control. Locking and timestamping are two popular approaches to concurrency control in database systems. Timestamp-based algorithms have been proposed to protect distributed databases from inconsistencies during concurrent access. In these algorithms, transactions may reach a particular site in different order than their timestamps, due to unexpected network delays. This causes conflicts which the distributed concurrency control mechanism has to cope with. We exhibit an analytical solution, which has been tested with extensive simulation. The accuracy seems to be very high. We assume perfect and also imperfect clocks for synchronization and quantify the way in which local clock inaccuracies affect the phenomenon of transaction conflicts. In particular, we derive a lot of interesting performance measures such as probability of abort, mean waiting time, throughput, mean queue length and others.1 aBouras, Christos1 aSpirakis, Paul uhttps://telematics.upatras.gr/telematics/publications/performance-modeling-distributed-timestamp-ordering-perfect-and-imperfect-clocks00433nas a2200133 4500008004100000245004000041210004000081300000800121100002100129700002300150700001900173700001600192856009100208 1996 eng d00aRandomized adaptive video on demand0 aRandomized adaptive video on demand a1791 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aPantziou, G uhttps://telematics.upatras.gr/telematics/publications/randomized-adaptive-video-demand02045nas a2200169 4500008004100000245007200041210006900113260001600182300001500198520143800213100002101651700002301672700001901695700002201714700001401736856012501750 1996 eng d00aTRENDS: Training Educators through Networks and Distributed Systems0 aTRENDS Training Educators through Networks and Distributed Syste c8 - 10 July a 195 - 1993 aThe TRENDS project aims at the in-service, distance training of 2,400 school teachers in Secondary Education, and the use of Information Technology and Telematics in the learning process, by six countries (Greece, Italy, Spain, Portugal, France, and United Kingdom). The training process will be implemented by flexible and distance learning methods, through the development and use of an in-service school-based training system, which will be based on multimedia telematics and existing mature network technologies, and the establishment and operation of a European Teacher’s Training Network, consisted of six interconnected National Sites (Training Centre, schools and teachers per country). Each Training Centre in the Network will act as service provider to the schools and the teachers. The major aspect of the project is to provide the educator and their trainers, with various services including : e-mail contact with other educators and trainers, access to multimedia information, forums for the discussion and debate on educational projects, access to curriculum-related information for the educators, and multimedia teletraining for the conduction of lessons over the network. Due to the nature of the planned services and applications, the network infrastructure that will be used for the realization of the TRENDS, must offer high speed, multicasting, trans-European interoperability and certified quality of services.1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aTsakarissianos, G1 aKastis, N uhttps://telematics.upatras.gr/telematics/publications/trends-training-educators-through-networks-and-distributed-systems01735nas a2200193 4500008004100000245005800041210005700099260001700156300001500173520111800188100002101306700002301327700001901350700001501369700001501384700001501399700002201414856010501436 1995 eng d00aHIPPOCRATES: A multimedia tool for distance education0 aHIPPOCRATES A multimedia tool for distance education c17 - 21 June a 103 - 1083 aIn this paper we present a software tool for the realisation of the distance education service, that is the conduction of classes through the use of computers. The classes are directed towards personnel in various areas and aim at the retraining and update of the personnel in subjects of special interest in their line of work. The conduction of classes takes place, from and towards, remote regions with the aid of a computer network. Hippocrates is a flexible and easy-to-use application, which permits students, who sit in front of remotely situated workstations, to attend classes or seminars given by a teacher or expert, who can also be located in some remote geographical area. Hippocrates can be thought of as a distributed transparency projector. The teacher can project transparencies on the screens of the students’ workstations and can emphasize or indicate regions of interest on them by using the graphical tools offered by Hippocrates. Immediate results of the use of Hippocrates are the fast updating of the personnel in remote areas and the upgrading of the quality of the services they offer.1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aLampsas, P1 aTatakis, A1 aFotakis, D1 aPapoutsopoulos, G uhttps://telematics.upatras.gr/telematics/publications/hippocrates-multimedia-tool-distance-education00970nas a2200193 4500008004100000245005300041210005300094260002800147300001500175520035400190100002100544700002300565700001900588700001500607700001500622700002000637700001500657856010400672 1995 eng d00aMultilingual Implementations of OSI Applications0 aMultilingual Implementations of OSI Applications c30 October - 1 November a 367 - 3743 aIn this work the problem of supporting multilingual environments over OSI applications is addressed. Initially a solution based on the idea of using multilingual structures and transcription techniques is presented. Another solution based on the major principles of the former follows, which exploits the coding of all of character sets uniformally.1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aLampsas, P1 aTatakis, A1 aKontogiannis, S1 aFotakis, D uhttps://telematics.upatras.gr/telematics/publications/multilingual-implementations-osi-applications00457nas a2200097 4500008004100000245008000041210006900121100002300190700001900213856012700232 1995 eng d00aRandomized Competitive Algorithms for Admission Control in General Networks0 aRandomized Competitive Algorithms for Admission Control in Gener1 aKapoulas, Vaggelis1 aSpirakis, Paul uhttps://telematics.upatras.gr/telematics/publications/randomized-competitive-algorithms-admission-control-general-networks00444nam a2200121 4500008004100000245004900041210004800090100002100138700002300159700001900182700001900201856010200220 1994 eng d00aDiscrete Mathematics: Problems and Solutions0 aDiscrete Mathematics Problems and Solutions1 aBouras, Christos1 aKirousis, Lefteris1 aSpirakis, Paul1 aVoutsadakis, G uhttps://telematics.upatras.gr/telematics/publications/discrete-mathematics-problems-and-solutions01472nas a2200133 4500008004100000245012300041210006900164260001600233300001500249520089200264100002101156700001901177856014201196 1993 eng d00aThe perfect and imperfect clocks approach to performance analysis of basic timestamp ordering in distributed databases0 aperfect and imperfect clocks approach to performance analysis of c27 - 29 May a 403 - 4073 aLocking and timestamping are two popular approaches to concurrency control in databases systems. Although more than a dozen analytic performance studies of locking techniques have recently appeared in the literature, analytic performance study of timestamp–based concurrency algorithms largely remains an unexplored area. This work presents a model of a distributed database system which provides the framework to study the performance of timestamp ordering concurrency control. We exhibit an analytical solution, which has been tested with extensive simulation. The accuracy seems to be very high. We assume perfect and also imperfect clocks for synchronization and quantify the way in which local clock inaccuracies affect the phenomenon of transaction conflicts. In particular, we derive a lot of interesting performance measures such as probability of abort, throughput and others.1 aBouras, Christos1 aSpirakis, Paul uhttps://telematics.upatras.gr/telematics/publications/perfect-and-imperfect-clocks-approach-performance-analysis-basic-timestamp-ordering01007nas a2200133 4500008004100000245010300041210006900144260002000213300001500233520044800248100002100696700001900717856013700736 1993 eng d00aPerformance Models for Perfect and Imperfect Clocks on Timestamp Ordering in Distributed Databases0 aPerformance Models for Perfect and Imperfect Clocks on Timestamp c17 - 20 January a 243 - 2463 aThis work presents a model of a distributed database system which provides the framework to study the performance of timestamp ordering concurrency control. We exhibit an analytical solution, which has been tested with extensive simulation. The accuracy seems to be very high. We assume perfect and also imperfect clocks for synchronization and quantify the way in which local clock inaccuracies affect the phenomenon of transaction conflicts.1 aBouras, Christos1 aSpirakis, Paul uhttps://telematics.upatras.gr/telematics/publications/performance-models-perfect-and-imperfect-clocks-timestamp-ordering-distributed00343nam a2200109 4500008004100000245002500041210002500066100002100091700002300112700001900135856007900154 1992 eng d00aDiscrete Mathematics0 aDiscrete Mathematics1 aBouras, Christos1 aKirousis, Lefteris1 aSpirakis, Paul uhttps://telematics.upatras.gr/telematics/publications/discrete-mathematics00560nas a2200157 4500008004100000245006200041210006100103260001700164300001500181100002100196700002300217700001900240700001800259700001400277856011100291 1992 eng d00aMIPL:An Image Processing Library for Medical Applications0 aMIPLAn Image Processing Library for Medical Applications c14 - 17 June a 519 - 5251 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aGeorgantas, T1 aGoutis, K uhttps://telematics.upatras.gr/telematics/publications/miplan-image-processing-library-medical-applications01260nas a2200133 4500008004100000245008400041210006900125260002100194300001300215520073700228100002100965700001900986856012101005 1991 eng d00aThe effect of clock drifts on the performance of distributed timestamp ordering0 aeffect of clock drifts on the performance of distributed timesta c12 - 14 December a 69 - 853 aTimestamp–based algorithms have been proposed to protect distributed database from inconsistencies during concurrent access. In such algorithms, transactions may reach a paricular site out of the order of their timestamps, due to unexpected network delays. This causes conflicts which the distributed concurrency control mechanism has to cope with. In this paper we analyze the essential features of the conflict phenomenon under the realistic assumption of the local site clocks out of total synchrony. We quantify the way in which local clock inaccuracies affect the phenomenon of transaction conflicts. In particular, we express the probability of order–reverse as a particular increasing function of the maximum clock drift.1 aBouras, Christos1 aSpirakis, Paul uhttps://telematics.upatras.gr/telematics/publications/effect-clock-drifts-performance-distributed-timestamp-ordering00583nas a2200157 4500008004100000245007100041210006900112260001400181300001300195100002100208700001900229700001900248700002200267700001800289856011800307 1991 eng d00aRECPHONE: A new environment for medical remote expert consultation0 aRECPHONE A new environment for medical remote expert consultatio c2 -3 July a 22 - 231 aBouras, Christos1 aSpirakis, Paul1 aGarofalakis, J1 aPapoutsopoulos, G1 aBasiroglou, P uhttps://telematics.upatras.gr/telematics/publications/recphone-new-environment-medical-remote-expert-consultation00584nas a2200121 4500008004100000245012500041210006900166260002800235300001500263100002100278700001900299856014400318 1990 eng d00aSimplified performance models of the reordering issue in timestamp ordering concurrency control in distributed databases0 aSimplified performance models of the reordering issue in timesta c30 October - 2 November a 719 - 7271 aBouras, Christos1 aSpirakis, Paul uhttps://telematics.upatras.gr/telematics/publications/simplified-performance-models-reordering-issue-timestamp-ordering-concurrency-control00559nas a2200145 4500008004100000245006800041210006800109260001600177300001500193100002100208700001900229700002700248700001900275856011900294 1987 eng d00aQueueing Delays in Buffered Multistage Interconnection Networks0 aQueueing Delays in Buffered Multistage Interconnection Networks c11 - 14 May a 111 - 1211 aBouras, Christos1 aSpirakis, Paul1 aTriantafillou, Vasilis1 aGarofalakis, J uhttps://telematics.upatras.gr/telematics/publications/queueing-delays-buffered-multistage-interconnection-networks