Preface BCI 09 is the fourth event in the series of the Balkan Conference in Informatics. It follows BCI 07 held in Sofia, BCI 05 in Ohrid, and the very first Conference in the series, BCI 03, which started in Thessaloniki. The aim of the conference is to provide a forum for discussions and dissemination of research achievements, to promote interaction and collaboration among scientists from the Balkans and beyond, and to encourage involvement of young researchers from the region. BCI 09 has taken place at the Capsis Hotel, in Thessaloniki, Greece, during 17-19 of September 2009. As a matter of fact, 125 manuscripts were submitted for consideration. The affiliation of the 303 authors participating in these papers are from 14 different countries, with the vast majority of them within the greater Balkan region, such as Albania, Bosnia and Herzegovina, Bulgaria, Croatia, Former Yugoslav Republic of Macedonia, Romania, Serbia, Slovenia, Turkey and Greece. From 125 papers, 41 were selected to be presented in the conference as full papers and were included in the proceedings volume at hand, while another 28 were selected for short presentation. The selection was based on an international peer review process by at least two independent academic reviewers per paper. The papers presented at the BCI 09 conference are classified under the following sessions: Software Agents E-Services Algorithms and Theory E-Learning Informatics Applications Computer Networks Artificial Intelligence Software Engineering Data Management Text Processing Distributed Systems Web Technologies Informatics Education Four distinguished scientists have been invited to give plenary talks in the conference: Keith Jeffery (Director, Rutherford Appleton Laboratory, UK), The New Technologies and the New Challenges for Informatics Dimitris Karagiannis (University of Vienna, Austria), Modelling Semantics in Service-Oriented Environment David White (EU Fellow, European University Institute, Florence, Italy), Creativity, Entrepreneurship, Innovation: Threats and Opportunities Michail Bletsas (Director of Computing, MIT Media Lab, USA), A Brief History of OLPC and What I Learned from It. Finally, we would like to thank: the Invited Speakers for accepting to participate in our Conference, the Programme Committee for their significant support at the scientific level, the Organizing Committee, which ensured the success of the Conference, Bob Werner and Andrea Thibault as well as their colleagues from the IEEE Computer Society Conference Publishing Services for their cooperation and their help during the publication process, and finally the Ministry of Education, the University of Macedonia at Thessaloniki, the Aristotle University of Thessaloniki, and the Alexander Technological Educational Institute of Thessaloniki, CITY Liberal Studies, the South-East European Research Center and the Greek Computer Society for their invaluable support. Thessaloniki, Greece, September 2009 Y. Manolopoulos, K. Margaritis General Chairs ix
Committees Conference Chair Yannis Manolopoulos (Aristotle University, Greece) Costas Margaritis (University of Macedonia, Greece) Organizing Committee George Eleftherakis (CITY College, Greece) (Co-chair) Christos Georgiadis (University of Macedonia, Greece) (Co-chair) Panagiotis Ketikidis (Greek Computer Society, Macedonia-Thrace Annex, Greece) (Co-chair) Programme Committee Christos Douligeris (University of Piraeus, Greece) (Co-chair) Petros Kefalas (South-East European Research Center, Greece) (Co-chair) Demosthenes Stamatis (Alexander TEI, Greece) (Co-chair) Costin Badica (Univ. of Craiova, Romania) Ivana Berkovic (Univ. of Novi Sad, Serbia) Zoran Budimac (Univ. of Novi Sad, Serbia) Mehmet Caglayan (Bogazici Univ., Turkey) Betim Cico (Ploytechnic Univ. of Tirana, Albania) Miroslav Ciric (Univ. of Nis, Serbia) Alex Delis ( Univ. of Athens, Greece) Zamir Dika (South East European Univ., FYROM) Kostas Dimopoulos (CITY College, Greece) Dimitris Dranidis (CITY College, Greece) Pavlos Efraimidis (Democritus Univ. of Thrace, Greece) Avram Eskenazi (Bulgarian Academy of Sciences, Bulgaria) George Evangelidis (Univ. of Macedonia, Greece) Bekim Fetaji (South East European Univ., FYROM) John Garofalakis (Univ. of Patras, Greece) George Gravvanis (Democritus Univ. of Thrace, Greece) George Grigoras (Univ. of Iasi, Romania) Takis Hartonas (Technological Educational Institute of Larissa, Greece) Natasa Hoic-Bozic (Univ. of Rijeka, Croatia) Florentina Hristea (Univ. of Bucharest, Romania) Nestor Ioannidis (Technological Educational Institute of Athens, Greece) Florentin Ipate (Univ. of Pitesti, Romania) Mirjana Ivanovic (Univ. of Novi Sad, Serbia) Nikitas Karanikolas (Technological Educational Institute of Athens, Greece) Evaggelos Kehris (Technological Educational Institute of Serres, Greece) Margita Kon-Popovska (Univ. of Ss Cyril & Methodius, FYROM) Eugenia Kovatcheva (Univ. of Sofia, Bulgaria) x
Bozo Krstajic (Univ. of Montenegro, Montenegro) Alp Kut (Eylul Univ., Turkey) Aristidis Likas (Univ. of Ioannina, Greece) Nicolae Magariu (Moldova State Univ., Moldova) Christos Makris (Univ. of Patras, Greece) Nenad Mitic (Univ. of Belgrade, Serbia) Simona Motogna (Univ. of Cluj, Romania) Stavros Nikolopoulos (Univ. of Ioannina, Greece) Roumen Nikolov (Univ. of Sofia, Bulgaria) Iliana Nikolova (Univ. of Sofia, Bulgaria) George Papadopoulos (Univ. of Cyprus, Cyprus) Iraklis Paraskakis (South-East European Research Center, Greece) Dana Petcu (Univ. of Timisoara, Romania) Elias Pimenidis (Univ. of East London, UK) Boris Rachev (Varna Technical Univ., Bulgaria) Ilias Sakellariou (Univ. of Macedonia, Greece) Spiros Skiadopoulos (Univ. of Peloponnese, Greece) Ioannis Stamelos (Aristotle Univ. of Thessaloniki, Greece) Yannis Theodordis (Univ. of Piraeus, Greece) Thrasivoulos Tsiatsos (Aristotle Univ. of Thessaloniki, Greece) Ozgur Ulusoy (Bilkent Univ., Turkey) Athena Vakali (Aristotle Univ. of Thessaloniki, Greece) Anca Vasilescu (Univ. of Brasov, Romania) Michalis Vazirgiannis (Athens Univ. of Economics and Business, Greece) George Vouros (Univ. of the Aegean, Greece) Tatjana Welzer (Univ. of Maribor, Slovenia) Husnu Yenigun (Univ. of Sabanci, Turkey) Stathis Zachos (National Technical Univ. of Athens, Greece) Katerina Zdravkova (Univ. of Ss Cyril & Methodius, FYROM) xi
Additional Reviewers Evangelos Bampas Costas Dimitracopoulos George Drosatos Marjan Druzovec Stiakakis Emmanouil Dimitris Fotakis Nikos Giatrakos Thanos Hatziapostolou Marko Hölbl Trayan Iliev Ivailo Ivanov Kalinka Kaloyanova Andreas Koskeris Remous Aris Koutsiamanis Panagis Magdalinos Gerasimos Marketos Nikos Pelekis Ervin Ramollari Ioanna Stamatopoulou Antonia Stefani Vasilios Stefanis Aimilia Tasidou Evangelos Theodoridis Georgios Voulalas xii
Prof Dimitris Karagiannis University of Vienna, Austria Modelling Semantics in Service-Oriented Environment When approaching the ideas of Modelling Semantics Requirements and Service-Oriented Environment from the business informatics viewpoint, it becomes essential not only to address the challenges of the business level but also to consider their alignment with a technical realisation. Our MOSE Approach Modelling Semantics in Service-Oriented Environment supports the following: a. the design of a coherent view, providing methods to align modelling concepts from different application domains. On business level there is the challenge to derive a coherent view influenced by business-, legal- and technology regulations. The proposed methodology consists of (1) the engineering of your business and the related services; (2) the corresponding service-oriented environment which has to be adequately used and (3) the corporation resources and assets that have to be evaluated. b. the enablement of formalisms for the interpretation in the given Service-Oriented Environment. Hence different formalisms are integrated via the meta-modelling approach in order to enable a technology-based representation. The meta-modelling approach is here proposed as a concept to integrate the modelling languages in use, to achieve different perspectives of the coherent view. c. the transformation between different modelling languages in order to execute the models. The Service-Oriented Environment is at this point introduced as a technology-paradigm that virtualises computer resources into executable services. Hence the concrete Service-Oriented Environment depends on the underlined technology and management. The aforementioned applications of Semantic Modelling have been applied in a set of EU-funded projects, which will be presented. Michail Bletsas Director of Computing, MIT Media Lab, USA A Brief History of OLPC and What I Learned from It As one of the initial members of the OLPC team, I had the opportunity to follow the project and contribute to it from its initial conception to implementation. In this talk I will try to explain the reasons behind the key decision that we made, describe the experiences from the various deployments and provide some personal insight on what could have been done differently. xiii
Prof Keith G. Jeffery Director Information Technology & International Strategy, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, UK The New Technologies and the New Challenges for Informatics GRIDs, CLOUDs and Web2.0 all offer exciting possibilities. These new technologies are discussed. However, none yet overcome some of the existing outstanding problems in informatics, and indeed they raise new problems. How do we maintain the concept of state, integrity and ACID (Atomicity, Consistency, Isolation, Durability) transactions in a world with millions of nodes, very fast streams of data from detectors and worldwide update, retrieval and processing of data? How do local policies of security, privacy and integrity affect massive systems of heterogeneous nodes? How do we maintain security and privacy across such dynamic systems? Can we build trust systems applicable to today s environment? It is noticeable that over the last 20 years storage systems have improved speeds, capacities and cost per unit of around 10**18; processor power similarly by around 10**15 but wide area telecommunications by only around 10**4. This poses problems for system designers. Similarly the very high cost of software production and maintenance will only become greater unless we change the model. A way forward is proposed based on SOKU (Service-Oriented Knowledge Utilities). David White EU Fellow, European University Institute, Florence, Italy Creativity, Entrepreneurship, Innovation: Threats and Opportunities Philosophy contains insights into creativity and how it comes about. While deductive logic and rhetoric generally narrow the scope of discussion, (although rhetoric involves the listener in the process of understanding), it is in mimesis that we find pointers to creativity and in the use of language, most evidently in poetic language, that we find the creation of surplus of meaning. This is characteristic of all language that invites interpretation. It works by enabling new worlds to be envisioned, and by inviting hearers to act in those worlds. Such creative interaction comes about in dialogue which, in turn, is the key to the policy issues raised by the conference. xiv