The Laboratory

The Graphics, Multimedia and GIS Laboratory of the Computer Engineering & Informatics Department of the University of Patras was established in 1994. The educational and research work of the laboratory is being executed within the framework of the Department's Computer Software Section. The primary activities of the laboratory include the following:

  • Τhe support of the Computer Engineering & Informatics Department’s undergraduate and postgraduate education.
  • Τhe theoretical research conducting aiming to promote scientific progress in the areas of expertise of its members.
  • Τhe development of Graphics, Multimedia, GIS, Medical Informatics and Telematics applications and tools within the frameworks of national and EU research projects and the innumerable graduate studies of the Department.

The Lab is fully equipped with state-of-the-art computer hardware and software development facilities. It hosts a fully equipped multimedia laboratory, supporting the educational process and the R&D activities of the department.

A. Tsakalidis,  Professor

Group members
I. Hatzilygeroudis, Associate Professor
C. Makris, Assistant Professor
V. Verykios, Associate Professor
S. Sioutas, Associate Professor
G. Tzimas, Assistant Professor
D. Tsolis, Assistant Professor

Research Activities
The Graphics, Multimedia and GIS Lab operates under the framework of the Computer Engineering & Informatics Department of the University of Patras, supporting the Department’s undergraduate and postgraduate education. The primary aim of the Lab is to conduct innovative research and development across a wide range of the various scientific areas of its member’s expertise. More specifically, the Lab’s main research activities lie within the following principal scientific areas:

  • Theoretical Computer Science: Data Structures, Advanced Data Structures & Computer Graphics, Computational Geometry, Effective Algorithms, Models and Analysis of Computer Systems
  • Algorithmic Data Management: Query Processing and Query Optimization in RAM and I/O model, P2P Query Processing, Distributed Query Processing, Parallel and Distributed Query Processing, Big Data (NoSQL, NewSQL), Overlays and Infrastructures for Efficient Big Data Storage.
  • Information Retrieval: Retrieval Algorithms and indexing techniques, Retrieval Models, Ontologies, Semantic Search, Social Networks.
  • Machine Learning: Data Analytics & Data Mining , Artificial Intelligence and Expert Systems, Learning to Rank techniques, new clustering algorithms, redundancy elimination in search results and reranking employing clustering algorithms, text mining, opinion mining.
  • Web Technologies: Web Engineering, Web Mining, Web Search, Cloud Computing,  Semantic Web, Web & Mobile applications, Web Services, e-Commerce, e-Learning, e-Health.
  • Multimedia: Educational Software, Computer Graphics, Data Compression Techniques, VoD Solutions.
  • Geographical Information Systems (GIS): Spatial Databases & Data Models, GIS Platforms & Solutions, Routing Algorithms, Decision Support Systems.
  • Bioinformatics: Genetic and epidemiological databases, Data Visualization, Text mining in Biomedical Literature, Human Protein Interactome

In the past thirty years, the Lab has collaborated with a significant number of national, as well as international public and private bodies (universities, research institutes, private companies, ministries, non-profit organizations), conducting research and development activities. Indicatively, some of them are:

  • Fraunhofer Institute, Germany
  • King’s College London
  • Loughborough University
  • Hellenic Telecommunications Organization S.A.
  • INTRASOFT S.A., SingularLogic S.A., UNISYSTEMS S.A.
  • Athens 2004 Olympic Games Organizing Committee
  • Hellenic Statistical Authority (EL.STAT.)

Recent projects and funding

  • “Border Geomatics Utilities for Area Reconnaissance & Decision Support - Border Guards", Program Cooperation 2011 (2013-2015).
  • “Thesaurus - Treasury for Adult Education”, GRUNDTVIG LEARNING PARTNERSHIPS (2013-2015)
  • “The genetic architecture of type 2 diabetes mellitus in the Greek population; susceptibility, management, and prediction of complications", THALIS ACTION, GSRT (2012 – 2015).
  • “Development of an integrated information environment for assessment and documentation of conservation interventions to cultural works/objects with Non Destructive Techniques (NDTs)”, THALIS ACTION, GSRT (2011-2015).
  • “Algorithms and Techniques for Personalized Search in online environments using the underlying semantics” (01/09/2010 - 1/09/2013) PhD supervisor for an Heraclitus II PhD Fellowship entitled.
  • “Coordination of Standards and Technologies for the Enrichment of Europeana”, FP7 - ICT PSP European Commission Linked Heritage (2011 -2013).
  • “Otremed - Tool for the Territorial Strategy of the MED Space”, MED 2007 - 2013 (2010-2013).
  • “DLA – Digital Local Agenda”, Interreg IVC (2010-2013).
  • "Employing the ISO/IEC 9126 standard for Product Quality Assessment" Greek Secretariat of Research and Technology (2006 - 2008)

Selected projects 

  • AMILLA – "Digital Exhibition" of the History of the Olympic Games, Hellenic Culture Organization S.A. (2007-2009)
  • STATOBJECT: Object-Oriented Approach to Official Statistics, IST (2002-2005)
  • Development of an Integrated Customer Management System for TELEPASSPORT HELLAS S.A. (2001-2002)
  • Collaborative Applications for the Organizing Committee of the "Athens 2004" Olympic Games, Sophia (1999-2000) 
  • DATAMED: Data Capturing and Interchange in the Mediterranean Countries, ESPRIT (1997-2000)
  • OSYDD: University of Patras’ Network–Integrated System for Administration of Wide Area Network of High Distinctness (Voice – Data) & Telecontrol of University Campus Infrastructure, OPEIT (1996-1999).


Recent Selected Publications

  • Nikolaos Nodarakis, Spyros Sioutas, Athanasios K. Tsakalidis, Giannis Tzimas: “Large Scale Sentiment Analysis on Twitter with Spark”. EDBT/ICDT Workshops 2016.
  • Nikos Nodarakis, Evaggelia Pitoura, Spyros Sioutas, Athanasios Tsakalidis, Dimitrios Tsoumakos and Yannis Tzimas “kdANN+: A Rapid AkNN Classifier for Big Data”, Transactions on Large Distributed and Knowledge-based Systems (TLDKS),  Springer, 24: 139-168 (2016).
  • Timothy M. Chan, Konstantinos Tsakalidis: Optimal Deterministic Algorithms for 2-d and 3-d Shallow Cuttings. ACM Symposium on Computational Geometry 2015: 719-732.
  • A. Kanavos, C. Makris and E. Theodoridis. Topic Categorization of Biomedical Abstracts. International Journal on Artificial Intelligence Tools (IJAIT) 24(1) 2015.
  • Peyman Afshani, Konstantinos Tsakalidis: Optimal Deterministic Shallow Cuttings for 3D Dominance Ranges. ACM SODA 2014: 1389-1398
  • Gerth Stølting Brodal, Spyros Sioutas, Kostas Tsichlas, Christos D. Zaroliagis: D2-Tree: A New Overlay with Deterministic Bounds. Algorithmica 72(3): 860-883 (2015), Springer.
  • Panagiotis Gerolymatos, Spyros Sioutas, Nikolaos Nodarakis, Alexandros Panaretos, Konstantinos Tsakalidis: SMaRT: A novel framework for addressing range queries over nonlinear trajectories. Journal of Systems and Software 105: 79-90 (2015), Elsevier.
  • Spyros Sioutas, Efrosini Sourla, Kostas Tsichlas, Christos D. Zaroliagis: D3-Tree: A Dynamic Deterministic Decentralized Structure. ESA 2015: 989-1000, Springer.
  • Angeliki Rapti, Spyros Sioutas, Kostas Tsichlas, Giannis Tzimas:
  • Virus Propagation in Multiple Profile Networks. ACM SIGKDD 2015: 975-984
  • Eleanna Kafeza, Andreas Kanavos, Christos Makris, Pantelis Vikatos: T-PICE: Twitter Personality Based Influential Communities Extraction System. BigData Congress 2014: 212-219
  • Ioannou, Z-M., Nodarakis, N., Sioutas, S., Tsakalidis, A., Tzimas, G.: Mining Biological Data on the Cloud – A MapReduce Approach. 3rd Mining Humanistic Data Workshop (MHDW 2014), Rhodes, Greece, 19-21 September, 2014
  • Zafeiria-Marina Ioannou, Christos Makris, George P. Patrinos, Giannis Tzimas: A set of novel mining tools for efficient biological knowledge discovery. Artif. Intell. Rev. 42(3): 461-478 (2014)
  • Kasse, P., Tsolis, D., Semantic archeological sites/monuments management system, The 5th International Conference On Information, Intelligence, Systems And Applications, ΙΕΕΕ - IISA 2014, 2-5 July 2014, Chania, Greece
  • Paschou, M., Papadimitriou, C., Nodarakis, N., Korezelidis, K., Sakkopoulos, E., Tsakalidis, A.: Enhanced Healthcare Personnel Rostering Solution using Mobile Technologies. Journal of Systems and Software
  • G.Brodal, A. Kaporis, A. Papadopoulos, S. Sioutas, K. Tsakalidis, K. Tsichlas “Dynamic 3-sided Planar Range Queries with Expected Doubly Logarithmic Time”, Theor. Comput. Sci. (TCS) 526:58-74 (2014), Elsevier.
  • Alexis C. Kaporis, Christos Makris, Spyros Sioutas, Athanasios K. Tsakalidis, Kostas Tsichlas, Christos D. Zaroliagis: Improved Bounds for Finger Search on a RAM. Algorithmica 66(2): 249-286 (2013)


Selected Publications

  • A.K. Tsakalidis, "Maintaining Order in a Generalized Linked List", Acta Informatica, Vol. 21, pp. 101-112, 1984
  • A. K. Tsakalidis, "AVL-Trees for Localized Search", Information and Control, Vol. 67, Nos 1-3, pp.173-194, 1985
  • K. Mehlhorn and A.K.Tsakalidis, "An Amortized Analysis of Insertions into AVL-Trees", SIAM Journal on Computing, Vol. 15, No 1, pp. 22-33, 1986
  • A. K. Tsakalidis, "The Nearest Common Ancestor in a Dynamic Tree", Acta Informatica, Vol. 25, pp. 37-54, 1988
  • K. Mehlhorn and A.K. Tsakalidis, "Chapter 6: Data Structures" pp. 302-341, Handbook of Theoretical Computer Science, Vol. 1, 2 Volumes, 37 Chapters, 48 authors, 2269 pages, Managing Editor: J. van Leeuwen (Utrecht), Advisory Board:  A.R. Meyer (Cambridge, MA), M. Nivat (Paris) M.S. Paterson (Coventry), D. Perrin (Paris) Elsevier Science Publishers (for Europe), co-published by MIT-Press (for USA, Canada and Japan), 1990
  • K. Mehlhorn and A.K. Tsakalidis, "Dynamic Interpolation Search", Journal of ACM, Vol. 40, No 3, pp. 621-634, 1993
  • Christos Makris, Athanasios K. Tsakalidis: Algorithms for Three-Dimensional Dominance Searching in Linear Space. Inf. Process. Lett. 66(6): 277-283 (1998)
  • Gerth Stølting Brodal, Christos Makris, Spyros Sioutas, Athanasios K. Tsakalidis, Kostas Tsichlas: Optimal Solutions for the Temporal Precedence Problem. Algorithmica 33(4): 494-510 (2002)
  • Gerth Stølting Brodal, George Lagogiannis, Christos Makris, Athanasios K. Tsakalidis, Kostas Tsichlas: Optimal finger search trees in the pointer machine. J. Comput. Syst. Sci. 67(2): 381-418 (2003).
  • Alexis C. Kaporis, Christos Makris, Spyros Sioutas, Athanasios K. Tsakalidis, Kostas Tsichlas, Christos D. Zaroliagis: Dynamic Interpolation Search Revisited. ICALP (1) 2006: 382-394.
  • A.Bakalis, C.Iliopoulos, Ch.Makris, S.Sioutas, E.Theodoridis, A.K. Tsakalidis, K.Tsichlas: Locating Maximal Multirepeats in Multiple Strings Under Various Constraints. Comput. J. 50(2): 178-185 (2007).
  • A.K. Tsakalidis,  “Some Results for elementary Operations”, Efficient Algorithms, Essays dedicated to Kurt Mehlhorn on the occasion of His 60th Birthday, eds. Susanne Albers, Helmut Alt, Stefan Naeher, Springer Verlag, LNCS 5760, pp. 121-133, 2009.
  • George Lagogiannis, Nikos A. Lorentzos, Spyros Sioutas, Evangelos Theodoridis:
    A time efficient indexing scheme for complex spatiotemporal retrieval. SIGMOD Record 38(3): 11-16 (2009).
  • Spyros Sioutas, George Papaloukopoulos, Evangelos Sakkopoulos, Kostas Tsichlas, Yannis Manolopoulos: “A novel distributed P2P simulator architecture: D-P2P-sim”, ACM  CIKM 2009: 2069-2070.
  • Alexis C. Kaporis, Apostolos N. Papadopoulos, Spyros Sioutas, Konstantinos Tsakalidis, Kostas Tsichlas: Efficient processing of 3-sided range queries with probabilistic guarantees. ICDT 2010: 34-43.
  • Spyros Sioutas, George Papaloukopoulos, Evangelos Sakkopoulos, Kostas Tsichlas, Yannis Manolopoulos, Peter Triantafillou: “ART--sub-logarithmic decentralized range query processing with probabilistic guarantees”. PODC 2010: 118-119.
  • Ioannis Konstantinou, Evangelos Angelou, Dimitrios Tsoumakos, Christina Boumpouka, Nectarios Koziris, Spyros Sioutas: TIRAMOLA: elastic nosql provisioning through a cloud management platform. SIGMOD Conference 2012: 725-728.
  • Maria I. Klapa, Kalliopi Tsafou, Evangelos Theodoridis, Athanasios K. Tsakalidis, Nicholas K. Moschonas: Reconstruction of the experimentally supported human protein interactome: what can we learn? BMC Systems Biology 7: 96, 2013.
  • Casper Kejlberg-Rasmussen, Yufei Tao, Konstantinos Tsakalidis, Kostas Tsichlas, Jeonghun Yoon: I/O-efficient planar range skyline and attrition priority queues. PODS 2013: 103-114
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