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Curriculum Vitae
PERSONAL INFORMATION
Full name: Eleftherios Tiakas
Date / Place of birth: 28/11/1972, Thessaloniki
Marital status: Married, 1 child
Military service: Fulfilled
Current position: Laboratory Teaching Staff
Department: Department of Informatics
University: Aristotle University of Thessaloniki (AUTH)
Work address: Data Engineering Laboratory, Department of
Informatics, AUTH, 54124, Greece
e-mail: [email protected]
URL: http://delab.csd.auth.gr/~tiakas/
BRIEF DESCRIPTION OF UNIVERSITY CAREER
I have received B.Sc. in Mathematics in 1994 from the Department of Mathematics, Faculty of
Sciences, Aristotle University of Thessaloniki. In 2004 I was appointed by the Ministry of
Education, through Supreme Council for Civil Personnel Selection, as a permanent Teacher of
Mathematics in Secondary Education. In 2006 I received a B.Sc. in Computer Science –
Informatics and a M.Sc. in Computer Science with focus on Information Systems. In 2011 I
received a Ph.D. from the Department of Informatics, Faculty of Sciences, Aristotle University of
Thessaloniki. From 2011 to 2017 I have been a postdoctoral researcher and adjunct lecturer
contracted in the Department of Informatics, AUTH. From 2017 until now I am in the Laboratory
Teaching Staff of the Department of Informatics, AUTH.
My areas of research interest include: Query Processing, Indexing, Databases, Spatial and
Multidimensional Databases, Data Structures, Data Mining, Information Retrieval, Similarity
Search, Social Networks, Bio-Informatics. I am the author of two theses (M.Sc. and Ph.D.). I am
the author/co-author of 12 articles published in international journals, 17 papers published in
international conference proceedings, 2 book chapters, and 3 technical reports. My publications
have already received over 450 citations from other scientific publications. I participated in 11
research projects/and programs funded by the European Union and Greece. Also, I was
responsible for supervising 2 theses during my PhD, and 3 postgraduate theses after. Finally,
from 2007 until now, I also serve as a regular/external reviewer and PC-Member in several
international journals and conferences.
EDUCATION
2005-2011: Ph.D. Diploma from the Department of Informatics, AUTH, with excellent
grade. Ph.D. thesis: “Similarity and domination query processing in
multidimensional spaces”.
2004-2006: M.Sc. Diploma in Computer Science with focus on Information Systems
(CSIS), Department of Informatics, AUTH, and excellent grade: 9.43 / 10.
Postgraduate thesis: “Trajectory similarity queries in spatial networks”.
2004-2006: B.Sc. Diploma in Computer Science with focus on Information Systems
(CSIS), Department of Informatics, AUTH, and excellent grade: 8.72 / 10.
Thesis: “Computing trajectories similarity with metric relations and applications
of range queries in spatial networks”.
1990-1994: B.Sc. Diploma in Mathematics with focus on Applied Mathematics,
Department of Mathematics, AUTH, and excellent grade: 8.56 / 10.
Languages
English (BULATS Certificate Β2).
RESEARCH INTERESTS
Big Data, Databases, Data Structures, Query Processing Algorithms, Indexing Structures, Spatial
and Multidimensional Databases, Spatial Databases, Multimedia Databases, Information Systems,
Data Mining, Information Retrieval, Similarity Search, Social Networks, Bio-Informatics, Medical
research, Algorithm Design and Analysis, Discrete Mathematics, Decision Support Systems, GIS,
Forest Modelling, Computational Geometry.
UNIVERSITY TEACHING EXPERIENCE
Spring 2019: Adjunct Lecturer (Laboratory Teaching Staff) of the postgraduate course:
“Advanced Topics in Databases”, Department of Informatics, AUTH.
Spring 2019: Teaching Assistant (Laboratory Teaching Staff) for the undergraduate course:
“Data Structures” of the 2nd
semester, Department of Informatics, AUTH.
Spring 2019: Teaching Assistant (Laboratory Teaching Staff) for the undergraduate course:
“Algorithms” of the 4th
semester, Department of Informatics, AUTH.
Fall 2018: Adjunct Lecturer (Laboratory Teaching Staff) of the joint postgraduate course:
“Databases”, Department of Informatics, AUTH.
Fall 2018: Teaching Assistant (Laboratory Teaching Staff) for the undergraduate course:
“Databases” of the 5th
semester, Department of Informatics, AUTH.
Fall 2018: Teaching Assistant (Laboratory Teaching Staff) for the undergraduate course:
“Discrete Mathematics” of the 1st semester, Department of Informatics, AUTH.
Fall 2018: Teaching Assistant (Laboratory Teaching Staff) for the undergraduate course:
“Operating Systems” of the 5th
semester, Department of Informatics, AUTH.
Spring 2018: Adjunct Lecturer (Laboratory Teaching Staff) of the joint postgraduate course:
“Databases and Data mining”, Department of Informatics, AUTH.
Spring 2018: Teaching Assistant (Laboratory Teaching Staff) for the undergraduate course:
“Data Structures” of the 2nd
semester, Department of Informatics, AUTH.
Spring 2018: Teaching Assistant (Laboratory Teaching Staff) for the undergraduate course:
“Algorithms” of the 4th
semester, Department of Informatics, AUTH.
Fall 2017: Adjunct Lecturer (Laboratory Teaching Staff) of the postgraduate course: “Spatial
and Multimedia Databases”, Department of Informatics, AUTH.
Fall 2017: Teaching Assistant (Laboratory Teaching Staff) for the undergraduate course:
“Databases” of the 5th
semester, Department of Informatics, AUTH.
Fall 2017: Teaching Assistant (Laboratory Teaching Staff) for the undergraduate course:
“Discrete Mathematics” of the 1st semester, Department of Informatics, AUTH.
Fall 2017: Teaching Assistant (Laboratory Teaching Staff) for the undergraduate course:
“Operating Systems” of the 5th
semester, Department of Informatics, AUTH.
Spring 2017: Adjunct Lecturer (contracted) of the joint postgraduate course: “Databases and
Data mining”, Department of Informatics, AUTH.
Spring 2017: Adjunct Lecturer (contracted according to the Presidential Decree 407/80 from
11-02-2017 to 30-06-2017) for co-teaching of 1 hour per week of the undergraduate course:
“Data Structures” of the 2nd
semester, Department of Informatics, AUTH.
Fall 2016: Adjunct Lecturer (contracted) of the postgraduate course: “Spatial and Multimedia
Databases”, Department of Informatics, AUTH.
Fall 2016: Adjunct Lecturer (contracted according to the Presidential Decree 407/80 from 15-
12-2016 to 10-02-2017) for co-teaching of 2 hours per week of the undergraduate course:
“Basic Programming Principles” of the 1st semester, Department of Informatics, AUTH.
Fall 2016: Teaching Assistant for the undergraduate course: “Databases” of the 5th
semester,
Department of Informatics, AUTH.
Fall 2015: Teaching Assistant for the undergraduate course: “Databases” of the 5th
semester,
Department of Informatics, AUTH.
Spring 2015: Adjunct Lecturer (contracted) of the postgraduate course: “Advanced Data
Indexing”, Department of Informatics, AUTH.
Fall 2014: Teaching Assistant for the undergraduate course: “Databases” of the 5th
semester,
Department of Informatics, AUTH.
Fall 2013: Teaching Assistant for the undergraduate course: “Databases” of the 5th
semester,
Department of Informatics, AUTH.
PUBLICATIONS
1. Journal Articles
[J12] Dimitris Zianis, Gavriil Spyroglou, Eleftherios Tiakas, Kalliopi Radoglou. "Bayesian and
classical models to predict aboveground tree biomass allometry", Forest Science Journal, vol. 62,
no. 3, pp. 247-259, June 2016.
[J11] Eleftherios Tiakas, George Valkanas, Apostolos N. Papadopoulos, Yannis Manolopoulos,
Dimitrios Gunopulos. "Processing Top-k Dominating Queries in Metric Spaces", Transactions on
Database Systems (ACM), vol. 40, no. 4, 38 pages, article 23, January 2016.
[J10] Zaigham Faraz Siddiqui, Eleftherios Tiakas, Panagiotis Symeonidis, Myra Spiliopoulou,
Yannis Manolopoulos. "Learning Relational User Profiles and Recommending Items as Their
Preferences Change", International Journal on Artificial Intelligence Tools (World Scientific
Publishing Company), vol. 24, no. 2, 31 pages, April 2015.
[J9] Nantia Iakovidou, Eleftherios Tiakas, Konstantinos Tsichlas, Yannis Manolopoulos. "Going
over the three dimensional protein structure similarity problem", Artificial Intelligence Review
(Springer), vol. 42, no. 3, pp. 445-459, October 2014.
[J8] Panagiotis Symeonidis, Eleftherios Tiakas. "Transitive node similarity: predicting and
recommending links in signed social networks", World Wide Web Journal (Springer), vol. 17, no. 4,
pp. 743-776, July 2014.
[J7] Eleftherios Tiakas, Apostolos N. Papadopoulos, Yannis Manolopoulos. "On Estimating the
Maximum Domination Value and the Skyline Cardinality of Multi-Dimensional Data Sets",
International Journal of Knowledge-Based Organizations (IGI Global), vol. 3, no. 4, pp. 61-83,
October 2013.
[J6] Eleftherios Tiakas, Dimitrios Rafailidis, Anastasios Dimou, Petros Daras. "MSIDX: Multi-
Sort Indexing for Efficient Content-Based Image Search and Retrieval", Transactions on
Multimedia (IEEE), vol. 15, no. 6, pp. 1415-1430, October 2013.
[J5] Panagiotis Symeonidis, Eleftherios Tiakas, Yannis Manolopoulos. "A unified framework for
link and rating prediction in multi-modal social networks", International Journal of Social Network
Mining (Inderscience), vol. 1, no. 3/4, pp. 225-253, January 2013.
[J4] Eleftherios Tiakas, Apostolos N. Papadopoulos, Yannis Manolopoulos. "Progressive
processing of subspace dominating queries", The VLDB Journal (Springer), vol. 20, no. 6, pp. 921-
948, December 2011.
[J3] Eleftherios Tiakas, Apostolos N. Papadopoulos, Alexandros Nanopoulos, Yannis
Manolopoulos. "Node and edge selectivity estimation for range queries in spatial networks",
Information Systems (Elsevier), vol. 34, no. 3, pp. 328-352, May 2009.
[J2] Eleftherios Tiakas, Apostolos N. Papadopoulos, Alexandros Nanopoulos, Yannis
Manolopoulos, Dragan Stojanovic, Slobodanka Djordjevic-Kajan. "Searching for similar
trajectories in spatial networks", Journal of System and Software (Elsevier), vol. 82, no. 5, pp. 772-
788, May 2009.
[J1] Eleftherios Tiakas, Stefanos Ougiaroglou, Petros Nicopolitidis. "Efficient algorithms for
constructing broadcast disks programs in asymmetric communication environments",
Telecommunication Systems (Springer), vol. 41, no. 3, pp. 185-209, May 2009.
2. Papers in Conference Proceedings
[C17] Theodoros Tzouramanis, Eleftherios Tiakas, Apostolos N. Papadopoulos, Yannis
Manolopoulos. "The Range Skyline Query", Proceedings of the 27th International Conference on
Information and Knowledge Management (ACM / CIKM), pp. 47-56, Torino, Italy, October 2018.
[C16] Nikolaos Georgiadis, Eleftherios Tiakas, Yannis Manolopoulos. "Detecting Intrinsic
Dissimilarities in Large Image Databases through Skylines", Proceedings of the 9th International
Conference on Management of Digital EcoSystems (ACM / MEDES), pp.194-201, Bangkok,
Thailand, November 2017, [Best Paper Award].
[C15] Alexander Tzanakas, Eleftherios Tiakas, Yannis Manolopoulos. "Skyline Algorithms on
Streams of Multidimensional Data", Proceedings of the 20th East-European Conference on
Advances in Databases and Information Systems (Springer / ADBIS), pp. 63-71, Prague, Czech
Republic, August 2016.
[C14] Eleftherios Tiakas, Dimitrios Rafailidis. "Scalable Trajectory Similarity Search Based on
Locations in Spatial Networks", Proceedings of the 5th International Conference on Model and
Data Engineering (Springer / MEDI), LNCS vol. 9344, pp. 213-224, Rhodes, Greece, September
2015.
[C13] Eleftherios Tiakas, Apostolos N. Papadopoulos, Yannis Manolopoulos. "Skyline Queries:
an Introduction (invited)", Proceedings of the 6th International Conference on Information,
Intelligence, Systems & Applications (IISA), 6 pages, Corfu, Greece, July 2015.
[C12] Eleftherios Tiakas, Apostolos N. Papadopoulos, Yannis Manolopoulos. "Top-k Dominating
Queries: a Survey (invited)", Proceedings of the 17th International Symposium on Programming
and Systems (ISPS), 10 pages, Algiers, Algeria, April 2015.
[C11] Zaigham Faraz Siddiqui, Eleftherios Tiakas, Panagiotis Symeonidis, Myra Spiliopoulou,
Yannis Manolopoulos. "xStreams: Recommending Items to Users with Time-evolving
Preferences", Proceedings of the 4th International Conference on Web Intelligence, Mining and
Semantics (ACM / WIMS), Article 22, 12 pages, Thessaloniki, Greece, June 2014.
[C10] Eleftherios Tiakas, George Valkanas, Apostolos N. Papadopoulos, Yannis Manolopoulos,
Dimitrios Gunopulos: "Metric-Based Top-k Dominating Queries", Proceedings of the 17th
International Conference on Extending Database Technology (Open Proceedings / EDBT), pp. 415-
426, Athens, Greece, March 2014.
[C9] Nantia Iakovidou, Eleftherios Tiakas, Konstantinos Tsichlas: "DISCO: A New Algorithm for
Detecting 3D Protein Structure Similarity", Proceedings of the Artificial Intelligence Applications
and Innovations Workshops (Springer / AIAI), pp. 622-631, Halkidiki, Greece, September 2012.
[C8] Panagiotis Symeonidis, Eleftherios Tiakas, Yannis Manolopoulos. "Product recommendation
and rating prediction based on multi-modal social networks", Proceedings of the 5th ACM
Conference on Recommender Systems (ACM / RECSYS), pp. 61-68, Chicago, IL, USA, October
2011.
[C7] Zaigham Faraz Siddiqui, Myra Spiliopoulou, Panagiotis Symeonidis, Eleftherios Tiakas. "A
Data Generator for Multi-Stream Data", Proceedings of the 2nd International Workshop on Mining
Ubiquitous and Social Environments (Springer / MUSE), pp. 63-70, Athens, Greece, September
2011.
[C6] Panagiotis Symeonidis, Eleftherios Tiakas, Yannis Manolopoulos. "Transitive node
similarity for link prediction in social networks with positive and negative links", Proceedings of
the 4th ACM Conference on Recommender Systems (ACM / RECSYS), pp. 183-190, Barcelona,
Spain, September 2010.
[C5] Eleftherios Tiakas, Apostolos N. Papadopoulos, Yannis Manolopoulos. "Estimation of the
Maximum Domination Value in Multi-dimensional Data Sets", Proceedings of the 14th East-
European Conference on Advances in Databases and Information Systems (Springer / ADBIS), pp.
505-519, Novi Sad, Serbia, September 2010.
[C4] Eleftherios Tiakas, Apostolos N. Papadopoulos, Yannis Manolopoulos. "Graph Node
Clustering via Transitive Node Similarity", Proceedings of the 14th Panhellenic Conference on
Informatics (IEEE / PCI), pp. 72-77, Tripoli, Greece, September 2010.
[C3] Eleftherios Tiakas, Apostolos N. Papadopoulos, Alexandros Nanopoulos, Yannis
Manolopoulos. "Selectivity estimation in spatial networks", Proceedings of the 23rd Annual
Symposium on Applied Computing (ACM / SAC), pp. 852-856, Fortaleza, Ceara, Brazil, March
2008.
[C2] Eletherios Tiakas, Stefanos Ougiaroglou, Petros Nicopolitidis. "Efficient broadcast disks
program construction in asymmetric communication environments", Proceedings of the 10th
International Symposium on Modelling, Analysis and Simulation of Wireless and Mobile Systems
(ACM / MSWiM), pp. 279-283, Chania, Crete Island, Greece, October 2007.
[C1] Eleftherios Tiakas, Apostolos N. Papadopoulos, Alexandros Nanopoulos, Yannis
Manolopoulos, Dragan Stojanovic, Slobodanka Djordjevic-Kajan. "Trajectory Similarity Search in
Spatial Networks", Proceedings of the 10th International Database Engineering & Applications
Symposium (IEEE / IDEAS), pp. 185-192, Delhi, India, December 2006.
3. Book Chapters
[CH2] Gavriil Spyroglou, Eleftherios Tiakas, Gregor Chatziphilippidis, Vasiliki Kazana. "The
design and use of forest decision support systems in Greece", Computer-based tools for supporting
forest management. The experience and the expertise world-wide (Epsilon Open Archive), pp. 152-
167, 2014.
[CH1] Theodoros Semertzidis, Dimitrios Rafailidis, Eleftherios Tiakas, Michael G. Strintzis,
Petros Daras. "Multimedia Indexing, Search and Retrieval in Large Databases of Social Networks",
Social Media Retrieval, Computer Communications and Networks series (Springer), pp. 43-63,
2012.
4. Technical Reports
[TR3] Nikolaos Georgiadis, Eleftherios Tiakas, Yannis Manolopoulos, Apostolos N.
Papadopoulos. "Skyline-based Dissimilarity of Images", Technical Report, Aristotle University of
Thessaloniki, 2019.
[TR2] Nikolaos Pliakis, Eleftherios Tiakas, Yannis Manolopoulos. "Efficient Progressive
Processing of Trajectories on Road Networks", Technical Report, Aristotle University of
Thessaloniki, 2018.
[TR1] Alexander Tzanakas, Eleftherios Tiakas, Yannis Manolopoulos. "Revisited skyline query
algorithms on streams of multidimensional data", Technical Report, Aristotle University of
Thessaloniki, 2016.
5. Theses
[TH3] Eleftherios Tiakas, “Similarity and domination query processing in multidimensional
spaces”, Ph.D. thesis (in Greek), Department of Informatics, AUTH, 2011.
[TH2] Eleftherios Tiakas, “Trajectory similarity queries in spatial networks”, Postgraduate thesis
(in Greek), Department of Informatics, AUTH, 2006.
[TH1] Eleftherios Tiakas, “Computing trajectory similarity with metric relations and applications
of range queries in spatial networks”, Thesis (in Greek), Department of Informatics, AUTH, 2006.
PARTICIPATION/INVOLVEMENT IN RESEARCH PROJECTS AND PROGRAMS
3/5/2017 - 31/7/2017: Research Project (no. 91875) with title: “Joint Postgraduate
Studies Programme “Informatics and Management””, Special
Account for Research Funds, AUTH.
Adjunct Lecturer (contracted) of the postgraduate course: “Databases
and Data mining” of the Department of Informatics, AUTH, for the
spring semester of 2017.
23/11/2016 - 28/2/2017: Research Project (no. 91877) with title: “Postgraduate Studies
Programme “Information and Communication Technologies””,
Special Account for Research Funds, AUTH.
Adjunct Lecturer (contracted) of the postgraduate course: “Spatial
and Multimedia Databases” of the Department of Informatics,
AUTH, for the fall semester of 2016.
8/4/2015 - 30/6/2015: Research Project (no. 21455) with title: “Services to connect
undergraduate and graduate students with the market”, Special
Account for Research Funds, AUTH.
Adjunct Lecturer (contracted) of the postgraduate course: “Advanced
Data Indexing” of the Department of Informatics, AUTH, for the
spring semester of 2015.
19/2/2015 - 30/6/2015: Research Project (no. 90410) with title: “15th
International
Conference on Web Information System Engineering (WISE
2014)”, Special Account for Research Funds, AUTH.
Assistant Editor and Internal Reviewer for the selection of papers
from the workshops of the conference WISE 2014, and their
publication in a post-proceedings volume by Springer.
1/8/2014 - 31/12/2014: Research Project (no. 89663) with title: “26th
International
Conference on Advanced Information Systems Engineering
(CAISE 2014)”, Special Account for Research Funds, AUTH.
Assistant Editor and Internal Reviewer for the selection of papers
from the proceedings of the conference CAISE 2014, and their
publication in a special issue of the Requirements Engineering
Journal by Springer.
9/11/2013 - 6/3/2014: Research Project (no. 89503) with title: “14th
International
Conference of Engineering Applications of Neural Networks
(EANN)”, Special Account for Research Funds, AUTH.
Assistant Editor and Internal Reviewer for the selection of papers
from the proceedings of the conference EANN, and their publication
in special issues of the scientific journals: Information Sciences and
Neurocomputing, by Elsevier.
2/4/2012 - 9/12/2012: Research Project 3Dlife: 3DLife is a network of excellence funded
by the European Union under THEME ICT-2009.1.5 “Networked
Media and 3D Internet” of the 7th
Framework Programme. 3DLife's
ultimate target is to lay the foundations of a European Competence
Centre under the name "Excellence in Media Computing &
Communication" or simply EMC2.
Researcher in 3DLife-EMC2 on a research project with title: “Multi-
Sort Indexing for Image Similarity Search”, in the area of Media
Computing & Communication and in cooperation with Information
Technologies Institute (ITI). After the successful completion of the
research, I received a scholarship and a fellowship diploma from
Queen Mary University of London.
1/1/2011 - 31/12/2012: Research Programme for the promotion of the exchange and
scientific cooperation between Greece and Germany (IKYDA
2011) with title: “Recommender Systems in Web2.0”.
Scientific cooperation between universities: (1) AUTH, and (2) Otto-
von-Guericke University, Magdemburg, Germany. The programme
was funded by the Greek State Scholarships Foundation (IKY).
Researcher – Member of the Greek research team. I designed and
implemented a recommendation system by combining social
networks’ data, social tags, user ratings and profiles.
26/1/2009 - 26/4/2013: Four-year European Research Project: FPS COST Action
FP0804, Forest Management Decision Support Systems
(FORSYS 2009-2013). The main objective of FORSYS was the
development of a European procedural framework, information
standards and guidelines, for the design, implementation, testing,
evaluation as well as the application of Decision Support Systems
(DSS) for forest management and multifunctional problems of
Forestry. In addition, to determine the requirements for the
application of DSS and to offer a consistent EU-wide quality
reference point for the development of DSS for forest management.
In this cost action, 24 countries participated along with Greece, with
national representatives, and 10 more institutions that do not belong
in the EU. It was funded by the European Commission, as part of the
EU RTD Framework Programme.
Researcher and active workgroup member in WG1: DSS architecture
and design, during the four years.
Moreover, I participated in almost all the meetings of the Working
Groups, which took place in various cities of the European Union.
4/12/2003 - 4/8/2004: Research Project with title: “Enhancing Computer Studies at the
Department of Applied Informatics, University of Macedonia of
Economic and Social Sciences”. The project was implemented
under the Operational Programme for Education and Initial
Vocational Training (O.P. “Education”). O.P. "Education" is one of
the Third Community Support Framework’s 24 Operational
Programmes (2000-2006) in Greece, and is co-financed by the
European Social Fund, the European Regional Development Fund
and national resources.
I worked as a programmer in this project (contracted), where:
a) I developed web applications and web databases that were hosted
on the website of University of Macedonia for the support of the
educational work and the promotion of the Postgraduate Studies
Programme.
b) I updated the website of University of Macedonia with educational
material from the various courses of the Postgraduate Studies
Programme of the Department of Applied Informatics of University
of Macedonia.
c) I checked, corrected and updated the lecture notes of the courses
“Design and Analysis of Algorithms” of the Undergraduate and the
Postgraduate Curriculum of the Department of Applied Informatics
of University of Macedonia (Instructor: Prof. K. Paparrizos).
1/11/2003 - 15/12/2003: Research Project “ITM” funded by the European Union in
collaboration with the Forest Research Institute of Thessaloniki
and the University of Vienna (BOKU).
Researcher and Programmer (contracted) on design and
implementation of a forest model management/simulator with 3D
graphics visualization capabilities using C++ and DirectX. I
developed a complete forest management simulation software
package entitled “DRYMOS” with the following main features: (i)
modeling and visualization of forest stands by using DirectX 3D
graphics, (ii) database management of forest stands data, (iii)
prediction and simulation of the evolution of the forest stands in
time, (iv) support of interactive tree plantings, tree thinning, snow
damages, regenerations into the stand, and various forestry scenarios.
The development of this software was made in the Forest Research
Institute of Thessaloniki and it was also presented at the National
Agricultural Research Foundation (N.AG.RE.F.).
PARTICIPATION IN CONFERENCES
International Conferences
o 2018 IEEE International Conference on INnovations in Intelligent SysTems and Applications
(INISTA), Thessaloniki, Greece, July 2018, (attendance).
o 21st International Conference on Theory and Practice of Digital Libraries (TPDL), Thessaloniki,
Greece, September 2017, (attendance).
o 16th
International Conference on Engineering Applications of Neural Networks (EANN),
Rhodes, Greece, September 2015, (session chair, attendance).
o 5th
International Conference on Model & Data Engineering (MEDI), Rhodes, Greece,
September 2015, (paper presentation, attendance).
o 15th
International Conference on Web Information System Engineering (WISE), Thessaloniki,
Greece, October 2014, (attendance).
o 20th
International Conference on Artificial Neural Networks and the collocated workshops
(ICANN), Thessaloniki, Greece, September 2010, (attendance).
o 5th
Conference on Artificial Intelligence Applications and Innovations and the collocated
workshops (AIAI), Thessaloniki, Greece, September 2009, (attendance).
o 10th
International Symposium on Modeling, Analysis and Simulation of Wireless and Mobile
Systems (MSWiM), Chania, Greece, October 2007, (paper presentation, attendance).
o 10th
East-European Conference on Advances in Databases and Information Systems (ADBIS),
Thessaloniki, Greece, September 2006, (attendance).
National Conferences
o 14th
Panhellenic Conference on Informatics (PCI), Tripoli, Greece, September 2010, (paper
presentation, attendance).
o 5th
Hellenic Data Management Symposium (HDMS), Thessaloniki, Greece, September 2006,
(attendance).
PARTICIPATION IN COST ACTIONS, MEETINGS, WORKSHOPS
AND OTHER PROGRAMS
International Meetings
o 3rd cHiPSet Training School “Large Scale Data Mining and Machine Learning for Big Data
Analytics”, of the COST Action IC1406 (cHiPSet) “High-Performance Modeling and
Simulation for Big Data Applications”, Thessaloniki, Greece, September 2018, (member).
o Final Work Group and Management Committee Meeting for EU Cost Action FP0804, Forest
Management Decision Support Systems (FORSYS), and parallel conference: “Decision support
systems for Sustainable Forest Management”, Umeå, Sweden, April 2013, (workgroup
member).
o 2nd
Meeting of IKYDA Research Program, Magdeburg, Germany, December 2011, (member).
o 5th
Work Group and Management Committee Meeting, EU Cost Action FP0804, Forest
Management Decision Support Systems (FORSYS), Leuven, Belgium, November 2011,
(workgroup member).
o 4th
Work Group and Management Committee Meeting, EU Cost Action FP0804, Forest
Management Decision Support Systems (FORSYS), Thessaloniki, Greece, June 2011,
(workgroup member).
o 3rd
Work Group and Management Committee Meeting, EU Cost Action FP0804, Forest
Management Decision Support Systems (FORSYS), Brussels, Belgium, October 2010,
(workgroup member).
o 2nd
Work Group and Management Committee Meeting, EU Cost Action FP0804, Forest
Management Decision Support Systems (FORSYS), Riga, Latvia, October 2009, (workgroup
member).
Workshops
o Educational Workshop with title: “3D Printing and Scanning - from theory to applications”,
Model-Experimental Senior High School of University of Macedonia, Thessaloniki, Greece,
January 2015, (member of the organizing committee, attendance).
o 3rd
Educational Workshop on New Technologies, Model-Experimental Senior High School of
University of Macedonia, Thessaloniki, Greece, December 2014, (member of the organizing
committee, educator, attendance):
I implemented the educational program: “Solving Geometry Problems with Geogebra”.
I participated also in the educational programs: “Edmodo: e-class”, “Interactive
presentations with Voicethread. On-line teaching through Web 2.0 tools”, “The design of a
simple web-page with Front Page”.
o Educational Workshop on Mathematics, 2nd
Model-Experimental Senior High School of
Thessaloniki, Greece, October 2014, (attendance).
o Educational Workshop with title: “Teaching of Mathematics, school necessities and university
involvement”, co-organized by the Department of Mathematics AUTH, Model-Experimental
Senior High-School of AUTH, and Model-Experimental Senior High-School of University of
Macedonia, Thessaloniki, Greece, 2014, (member of the organizing committee, attendance).
o 2nd
Educational Workshop on New Technologies, Model-Experimental Senior High School of
University of Macedonia, Thessaloniki, Greece, December 2013, (member of the organizing
committee, educator, attendance):
I implemented the educational program: “OCR-Tools for recognizing and reading general
and scientific documents”.
I participated also in the educational program: “Introduction to Hot Potatoes”.
o 1st Educational Workshop on New Technologies, Model-Experimental Senior High School of
University of Macedonia, Thessaloniki, Greece, December 2011, (member of the organizing
committee, educator, attendance):
I implemented the educational program: “Word processing with LaTeX”.
I participated also in the educational programs: “Web 2.0”, “Usage of interactive
whiteboards in the Natural Sciences and in Education in general”.
o 3rd
Student Conference on Informatics, Science Center and Technology Museum "NOESIS",
Thessaloniki, Greece, May 2011, (supervisor, paper presentation).
o Educational Workshop on Teaching of Mathematical Logic and Proof, Thessaloniki, Greece,
September 2010, (attendance).
o Scientific Conference on Innovation and Research in the Experimental School, University of
Macedonia, Thessaloniki, Greece, May 2010, (paper presentation, attendance).
Programs
o Internships Program Spring 2017, Department of Mathematics, Aristotle University,
Thessaloniki, Greece. I supported the internships program as a supervisor to student groups
(8/2/2017-7/4/2017).
o Internships Program Fall 2016, Department of Mathematics, Aristotle University,
Thessaloniki, Greece. I supported the internships program as a supervisor to student groups
(1/11/2016-31/12/2016).
o Internships Program Spring 2016, Department of Mathematics, Aristotle University,
Thessaloniki, Greece. I supported the internships program as a supervisor to student groups
(1/4/2016-31/5/2016).
o Educational Program “Youth Activ” within the Framework “Jean Monnet – Action KA1:
Information and Research Activities”, implemented by the University of Piraeus, Greece, March
2014, (workgroup member, attendance).
o Educational Program and Workshop with title: “Re-enforcing of the cultural potential of
students through formal, semi-formal and informal school practices”, Model-Experimental
Senior High School of University of Macedonia, Thessaloniki, Greece, March 2014, (member
of the organizing committee, workgroup member, attendance).
o Educational Program on New Technologies for the materialization of Projects and the formation
of teaching material, Model-Experimental Senior High School of University of Macedonia,
Thessaloniki, Greece, September 2013, (member of the organizing committee, attendance).
Invited Lectures - Talks
December 2013: Lecture with title: “Applications in Spatial Networks”, in the postgraduate
course: “Spatial Databases and GIS” (Fall Semester), Department of Informatics, AUTH.
May 1993: Research on theoretical models of Lebesque and on presentation of Peano space-
filling curves using computer graphics. Lecture with the title: “The space-filling curve of
Lebesque” in the Analysis Seminar in the Department of Mathematics, AUTH. (Archive of
Analysis Seminars 1992-2015, file manager: Prof. Dimitrios Betsakos).
February 1992: Research on algorithmic processing of theorems and examples from
Mathematical Analysis, and implementation of the studied algorithms, e.g. (a) general solution
of the polynomial equation of 3rd
degree, (b) solution of differential equations of 2nd
degree,
etc., Lecture for the results of this research in the Sector of Mathematical Analysis, Department
of Mathematics, AUTH.
March 1991: Research on developing computer graphics applications, which depict and
manage several types of mathematical functions (real, parametric, complex, multidimensional,
etc.) for educational and research purposes. Lecture for the results of this research in the Sector
of Mathematical Analysis, Department of Mathematics, AUTH.
PC-MEMBER
23rd International Database Engineering & Applications Symposium (IDEAS-2019)
9th International Conference on Web Intelligence, Mining and Semantics (WIMS-2019)
8th International Conference on Web Intelligence, Mining and Semantics (WIMS-2018)
REGULAR / EXTERNAL REVIEWER
in International Journals
The International Journal on Very Large Data Bases (VLDB) / Springer
Transactions on Knowledge and Data Engineering (TKDE) / IEEE
Data and Knowledge Engineering (DATAK) / Elsevier
Information Sciences (INS) / Elsevier
Big Data Research (BDR) / Elsevier
Distributed and Parallel Databases (DAPD) / Springer
Knowledge and Information Systems (KAIS) / Springer
International Journal of Data Science and Analytics (JDSA) / Springer
Transactions on Emerging Topics in Computing (TETC) / IEEE
Access / IEEE
Transactions on Neural Networks and Learning Systems (TNNLS) / IEEE
International Journal of Computer Systems Science and Engineering (IJCSSE) / CRL
Publishing
Engineering Intelligent Systems (EIS) / CRL Publishing
Journal of Computer Engineering and Information Technology (JCEIT) / SciTechnol
International Journal of Data Warehousing and Mining (IJDWM) / IGI Global
Information / MDPI
Informatics / MDPI
International Journal of Geo-Information (ISPRS) / MDPI
Symmetry / MDPI
Progress in Electromagnetic Research (PIER) / EMW Publishing
Journal of Electromagnetic Waves and Applications (JEMWA) / Taylor & Francis
Security and Communication Networks (SCN) / John Wiley & Sons, Ltd.
Software: Practice and Experience (SPE) / John Wiley & Sons, Ltd.
Complexity / John Wiley & Sons, Ltd.
International Journal of Security and Networks (IJSN) / Inderscience
International Journal of Advanced Intelligence Paradigms (IJAIP) / Inderscience
International Journal of High Performance Computing and Networking (IJHPCN) / Inderscience
Entropy / MDPI
Applied Sciences / MDPI
Mathematical and Computational Applications (MCA) / MDPI
Future Generation Computer Systems (FGCS) / Elsevier
Sensors / MDPI
Computer Science and Information Systems journal (ComSIS)
in International Conferences
International Conference on Data Engineering (ICDE)
International Conference on Extending Database Technology (EDBT)
International Conference on Knowledge Discovery and Data Mining (KDD)
International Conference on Advances in Geographic Information Systems (SIGSPATIAL-GIS)
International Symposium on Spatial and Temporal Databases (SSTD)
East-European Conference on Advances in Databases and Information Systems (ADBIS)
European Conference on Machine Learning and Principles and Practice of Knowledge
Discovery in Databases (ECML/PKDD)
International Conference on Database Systems for Advanced Applications (DASFAA)
International Conference on Statistical and Scientific Database Management (SSDBM)
International Conference on Recommender Systems (RECSYS)
International Conference on Web Information Systems Engineering (WISE)
International Conference on Web Intelligence, Mining and Semantics (WIMS)
International Conference on Artificial Neural Networks (ICANN)
International Conference on Mobile Data Management (MDM)
International Conference on Global Communications (GLOBECOM)
International Conference on Communications (ICC)
International Conference on Wireless Communications and Networking (WCNC)
International Conference on Connected Vehicles and Expo (ICCVE)
International Symposium on Programming and Systems (ISPS)
International Symposium on Intelligent Distributed Computing (IDC)
International Conference on Enterprise Information Systems (ICEIS)
International Joint conference on Software Technologies (ICSOFT)
International Conference on Mobile, Ubiquitous, and Intelligent Computing (MUSIC)
THESIS SUPERVISING
1. Thesis (in Greek): "Study and implementation of shortest path algorithms", Department of
Informatics, AUTH, Dimitra Papadimitriou, 2007.
2. Thesis (in Greek): "Search and study of methods for node labeling in large graphs", Department
of Informatics, AUTH, Thomas Kotios, 2010.
3. Postgraduate Thesis (in Greek): "Skyline query algorithms on streams of multidimensional
data", Department of Informatics, AUTH, Tzanakas Alexandros, 2016.
4. Postgraduate Thesis (in Greek): "Skyline query algorithms on large image databases",
Department of Informatics, AUTH, Georgiadis Nikolaos, 2016.
5. Postgraduate Thesis (in Greek): "Location-based trajectory similarity query algorithms in spatial
networks", Department of Informatics, AUTH, Pliakis Nikolaos, 2017.
TEACHING EXPERIENCE IN PUBLIC EDUCATION
Educator of Teachers of Secondary Education:
4/11/2009 - 16/11/2009: Educator of Teachers in Mathematics in the “Introductory Teacher
Training Program”, 3rd
Phase, 2nd
Regional Training Center of
Thessaloniki.
1/9/2008 - 10/9/2008: Educator of Teachers in Informatics in the project “Education and
Training of Teachers of Informatics”, part of the project “Training
Actions of Teachers of Informatics”, of the Operational Programme
“Information Society” of the 3rd
Community Support Framework
(CSF), 2nd
Educational Period, AUTH.
20/5/2008 - 31/5/2008: Educator of Teachers in Informatics in the project “Education and
Training of Teachers of Informatics”, part of the project “Training
Actions of Teachers of Informatics”, of the Operational Programme
“Information Society” of the 3rd
Community Support Framework
(CSF), 1st Educational Period, AUTH.
4/9/2007 - 13/9/2007: Educator of Teachers in Mathematics in the project «Intensive
Training Programs of Teachers of Secondary Education in the new
Teaching Packages”, organized by the Pedagogical Institute and the
Ministry of Education, and supported by the 3rd
Community Support
Framework (CSF) and the Operational Programme for Education and
Initial Vocational Training (O.P. “Education”), 2nd
Educational
Period, Regional Directory of Primary and Secondary Education of
Central Macedonia.
25/6/2007 - 27/6/2007: Educator of Teachers in Mathematics in the project «Intensive
Training Programs of Teachers of Secondary Education in the new
Teaching Packages”, organized by the Pedagogical Institute and the
Ministry of Education, and supported by the 3rd
Community Support
Framework (CSF) and the Operational Programme for Education and
Initial Vocational Training (O.P. “Education”), 1st Educational
Period, 2nd
Regional Training Center of Thessaloniki.
Organization of Educational Excellence Groups in the Secondary Education:
1. Organization of an Educational Excellence Group on “Astronomy” at the Model-Experimental
Senior High School of the University of Macedonia, and teaching in the school years: 2013-
2014, 2014-2015, 2015-2016, 2016-2017.
2. Organization of an Educational Excellence Group on “Web 2.0 Tools” at the Model-
Experimental Senior High School of the University of Macedonia, and teaching in the school
year 2012-2013.
Teacher of Secondary Education (permanent staff) of the Ministry of Education:
1. Teacher of Mathematics, Informatics and Astronomy in the Model-Experimental Senior High
School of the University of Macedonia, Thessaloniki, in the school years from 2009-2010 to
2016-2017.
2. Teacher of Mathematics, Informatics and Astronomy in the 1st Model-Experimental Senior
High School of Thessaloniki, in the school year 2008-2009.
3. Teacher of Mathematics in the High School of Meliki, Imathia, in the school year 2007-2008.
4. Teacher of Mathematics in the 2nd
Technical Vocational School of Alexandria and in the
High School of Trikala, Imathia, in the school year 2006-2007.
5. Teacher of Mathematics in the 2nd
Technical Vocational School of Veria, Imathia, in the
school year 2005-2006.
6. Teacher of Mathematics in the 2nd
Senior High School of Naousa, Imathia, in the school year
2004-2005.
Publications with Educational Content
Eleftherios Tiakas, Athanasiadis Ioannis, Ataloglou Vasileios, Toulikas Georgios, Tsingaras
Vyronas, “Drawing with Mathematical Equations”, 3rd
Student Conference on Informatics, 5
pages (in Greek), Science Center and Technology Museum “NOESIS”, Thessaloniki, May
2011.
Eleftherios Tiakas, “Simulating Trajectories of Solar System Objects and Phenomena in
Astronomy”, Conference on Innovation and Research at the Experimental School, 11 pages (in
Greek), University of Macedonia, Thessaloniki, May 2010.
2004-2005: I developed, as an innovation (because existing programs did not support certain
automation in designing and measuring geometric shapes and function graphs), specific
educational software to support teaching of chapters of Analysis and Geometry. This software
published on the web site www.e-yliko.gr (Educational Portal) of the Ministry of Education.
TEACHING EXPERIENCE IN PRIVATE EDUCATION
Teacher of Mathematics:
1993-2004: Teacher of Mathematics in Private Education Institutes and Private Schools.
a) Teaching Algebra, Analysis, Geometry, Analytic Geometry, Statistics to students attending
Primary, Lower Secondary and Upper Secondary Schools.
b) Teaching university courses to postgraduate and undergraduate students: Linear Algebra,
Analytic Geometry, Differential and Integral Calculus, Differential Equations, Linear
Programming, Number Theory, Applied Statistics.
Teacher of Informatics and Computer Science:
1. 1993-2003: Teacher of Computer Science and Informatics in the Private Education Institute
“Logica Computers”, to:
a) groups of postgraduate and undergraduate students,
b) groups of students attending Primary, Lower Secondary and Upper Secondary Schools,
c) special groups of professionals and individuals.
Courses taught:
o Primitive Systems and Programming Languages: Assembly language of Z80 and Motorola
6800 processors, and BASIC language of home micros: Texas Instruments TI99/4A, MSX-
Daewoo, Spectrum 16-48+, Amstrad 464-664-6128, Commodore 64-128, Amiga 500-1000.
o Accounting Commercial Software Packages: of Computer Logic, Singular and Unisoft
companies: “Horizons – General Accounting”, “Horizons – Commercial Management”,
“Warehouses and Sales Management”, “Mirage”, “Defacto”, “Personel”, and other packages
for accounting bookkeeping of B and C category.
o Programming Languages: Basic, Visual Basic, Visual Basic for Applications (VBA), Data
Access Objects (DAO), Fortran, Cobol, Pascal, Delphi, C, C++, Visual C++, SQL (Access-
SQL, SQL-Server, Oracle-SQL, MySQL), advanced graphics & sound programming,
Active-X Controls, Assembly 8088, 80x86 with MMX advanced graphics & sound
instructions, Direct-X Programming 2D-3D & advanced, OpenGL, HTML, XML, PHP,
JAVA Script, JAVA, Action Script, Prolog, Lisp, Clips, Strips, Object Oriented
Programming, UML.
o Operating Systems and Popular Software Packages: DOS, Windows, UNIX, LINUX, Word,
Excel, Access, Power Point, Data Base III-IV, Oracle, Page Maker, Corel Draw, Photoshop,
Internet Explorer, Outlook Express, Front Page, Wavelab, Sound Forge, Acid, Cubase, 3D
Studio, Vegas Video, Adobe Premier, Flash, AutoCAD, SPSS, MatLab, Mathematica.
o University Topics and Courses: Operating Systems, Databases, Networks, Principles of
Software Engineering, Software Design, Artificial Intelligence, Neural Networks,
Telematics and Internet, Informatics and Education, Discrete Mathematics, Analysis of
Algorithms, Data Structures, Digital Systems, Compilers, Grammars, Finite Automata,
Turing Machines.
2. December 1993: Teacher of Informatics in funded projects by the European Economic
Community (EEC). Teaching general use of computers and basic programming skills to special
groups of professionals and individuals.
COMPUTER PROGRAMMER/DEVELOPER IN COMPANIES (FREE-LANCER)
8/1/2000 – 31/8/2004:
1/9/2004 – 20/11/2012:
Computer Programmer/Developer in “TreeSoft” Software
Company, Alexandroupoli, Greece, which provides software
solutions and tools to Construction Companies, Contractors,
Engineers and Public Organizations, for more efficient management
of their files and archives.
I designed, developed and implemented business software
packages: ERP Systems, Logistics, Accounting Applications, and
several other specialized applications for: (a) Municipality
Management, (b) Lawyer Office Management, (c) Organization of
Activities, (d) Technical Works and Constructions Management, (e)
Public Works and Constructions Management, (f) Urban Buildings
Constructions Management.
I supported and upgraded the developed software packages whenever there was a requirement.
10/1/1998 - 21/12/2002: Computer Programmer/Developer in Jeronimo Groovy Radio
Station, Athens, Greece.
I designed, developed and implemented a specific management
application of the radio station for the compilation of its
broadcast program, which: (a) manages multimedia databases with
audio mp3 files and additional data, (b) recognizes and categorizes
the audio files in specific groups, (c) designs and constructs
automatically the playlist programs of the radio station for its
broadcast, based on several user-specific simple or complex criteria.
3/12/1993 - 31/8/2003: Computer Programmer/Developer in “Logica Computers”
business, Thessaloniki, Greece.
I designed, developed and implemented several specific software
packages to customers of the company, about:
o Warehouse and Products Management
o Customers and Suppliers Management
o Sales Management
o Accounting and Financial Applications
o Database Management
o Management of Multi-User Databases in Local Networks
o Music Editing Applications
o 3D Graphics and Animation Modeling Applications
o Encoding-Decoding and Cryptography Applications
o Educational Software
o Educational Games
Computer Service Technician in “Logica Computers” business,
Thessaloniki, Greece. During these ten years I experienced in a
wide variety of technical repairs in hardware, in software, in
maintenance of computer parts and peripherals, in system upgrades,
in computer assembling, as well as in installation of operating
systems, drivers and programs.
ADDITIONAL EDUCATION
2004 -2005: Introductory Teacher Training Program (1
st, 2
nd and 3
rd Phase), 1
st Regional
Training Center of Thessaloniki.
2003: ECDL-Advanced Diploma (Module 5 – Data Bases).
2003: ECDL Diploma (Windows, Word, Excel, Access, Power Point, Internet
Explorer, Outlook Express).
ADMINISTRATIVE RESPONSIBILITIES
1. 22/4/1996 - 31/8/2003: Managing Director of the company “Logica Computers”.
2. 3/4/2002 - 31/8/2004: Managing Member and Director of the Music-Record Company:
“Triangle Records Co.”.
MUSIC EDUCATION AND SKILLS
Music studies: classical piano lessons (7 years), music harmony, music creation, composition,
instrumentation, recording and production of music tracks.
Specialized knowledge in music creation, composition, instrumentation, recording and
production of music tracks using computer hardware & software applications and tools.
Specialized knowledge in: hardware & software analog and digital musical instruments,
synthesizers, samplers, sequencers, drum-machines, keyboards, sound editors, converters,
recorders, sound cards, effect machines, filters, compressors, amplifiers, and equalizers.
Specialized knowledge in programming of sound cards, and in music software development.
I composed over 100 completed music songs and tracks (instrumentations, productions,
remixes, remakes and new arrangements). Several of these songs and tracks were great radio
hits and published by the following record companies: FM-Records SA, Erial Records SA,
Warner Music SA, and Triangle Records (1996-2018).
Member of the Hellenic Society for the Protection of Intellectual Property (AEPI, 2002-2018).
HONORS - AWARDS - SCHOLARSHIPS
2012: Award from Queen Mary University of London for completing a 3DLife-EMC2
fellowship with a research project in the area of Media Computing & Communication.
2006: Award and Scholarship from the State Scholarships Foundation - IKY due to excellent
performance during undergraduate studies in the academic year 2005-2006 at the Department of
Informatics, AUTH.
1993: Award and Scholarship from the State Scholarships Foundation - IKY due to excellent
performance during undergraduate studies in the academic year 1992-1993 at the Department of
Mathematics, AUTH.
1992: Award and Scholarship from the State Scholarships Foundation - IKY due to excellent
performance during undergraduate studies in the academic year 1991-1992 at the Department of
Mathematics, AUTH.
1991: Award and Scholarship from the State Scholarships Foundation - IKY due to excellent
performance during undergraduate studies in the academic year 1990-1991 at the Department of
Mathematics, AUTH.
1991: Award and Scholarship from the Department of Meteorology and Climatology of
AUTH for the construction of a flexible computer application for the management and the
processing of meteorological data and forecasting models.
1990: Candidate member of the 2nd
International Olympiad in Informatics, Minsk, Belorussian
Republic, Soviet Union (IOI’90).
1990: Award due to excellent performance in the 2nd
National Competition of Informatics
organized by Greek Computer Society, Athens, Greece.
1990: Candidate member of the 31st International Olympiad in Mathematics, Beijing, China.
1989: Silver Medal in the 6th
National Olympiad in Mathematics organized by the Hellenic
Mathematical Society, Athens, Greece.
1989: Award due to excellent performance in the 49th
National Competition in Mathematics
organized by the Hellenic Mathematical Society, Greece.
1988: Award due to excellent performance in the 5th
National Olympiad in Mathematics
organized by the Hellenic Mathematical Society, Athens, Greece.
1988: Award due to excellent performance in the 48th
National Competition in Mathematics
organized by the Hellenic Mathematical Society, Greece.
1988: Award for participation in the 1st Balkan Summer School for talented young students in
Mathematics, organized by the Hellenic Mathematical Society, Ioannina, Greece.
1987: Bronze Medal in the 4th
National Olympiad in Mathematics organized by the Hellenic
Mathematical Society, Athens, Greece.
1987: Award due to excellent performance in the 47th
National Competition in Mathematics
organized by the Hellenic Mathematical Society, Greece.
1986: Award due to excellent performance in the 3rd
National Olympiad in Mathematics
organized by the Hellenic Mathematical Society, Athens, Greece.
1986: Award due to excellent performance in the 46th
National Competition in Mathematics
organized by the Hellenic Mathematical Society, Greece.
1986-1990: Publish of my specialized solutions to several problems of Olympiads in
Mathematics and Mathematical Competitions, in specific issues of the journals: “Euclid” and
“Dimension” of the Hellenic Mathematical Society, Athens.
Citations Table*
Top Publication Year Number of citations
Journal Articles 1 J2 2009 78
2 J8 2014 35
3 J4 2011 26
4 J6 2013 25
5 J3 2009 10
6 J7 2013 6
7 J10 2015 4
8 J5 2013 4
9 J11 2016 3
10 J12 2016 2
11 J9 2014 1
Conference Papers 1 C6 2010 100
2 C8 2011 77
3 C1 2006 45
4 C10 2014 16
5 C11 2014 8
6 C4 2010 7
7 C13 2015 4
8 C3 2008 4
9 C7 2011 2
10 C2 2007 2
11 C15 2016 1
12 C12 2015 1
13 C5 2010 1
Book Chapters 1 CH1 2012 3
Technical Reports 1 TR1 2016 2
Total number of Citations: 467 * The numbers are based on the results from Google Scholar as recorded on 31 January 2019.
Links
Partial list of citations from Google Scholar.
Partial list of publications from the Data Engineering Lab, Department of Informatics, Aristotle
University of Thessaloniki, Greece.
Partial list of publications from DBLP.
Partial list of citations from Microsoft Academic Search.
Partial list of publications from DBLife.
Partial list of publications from the Collection of Computer Science Bibliographies.
Publication Analysis
Journal Articles
J1. Eleftherios Tiakas, Stefanos Ougiaroglou, Petros Nicopolitidis. "Efficient algorithms for
constructing broadcast disks programs in asymmetric communication environments",
Telecommunication Systems (Springer), vol. 41, no. 3, pp. 185-209, May 2009.
A well-known technique for broadcast program construction is the Broadcast Disks technique.
However, in the Broadcast Disks approach there are some important disadvantages. For
example some parts of the broadcast program remain empty during the construction procedure
and the disk relative frequencies have to be selected very carefully. This paper gives a new
approach of the broadcast program construction in a Broadcast Disk System, presenting three
new algorithms, which face successfully these problems. According to this approach, the
broadcast program is constructed with the minimum possible length, while retaining the selected
disk relative frequencies and keeps the average delays on retrieving data-items low. The
constructed broadcast programs have no empty parts, and retain their desired properties in any
numbered combination of disk relative frequencies. We implemented all methods in a simulator
application and experimental results show that our approach is more efficient than Broadcast
Disks in all cases.
J2. Eleftherios Tiakas, Apostolos N. Papadopoulos, Alexandros Nanopoulos, Yannis
Manolopoulos, Dragan Stojanovic, Slobodanka Djordjevic-Kajan. "Searching for similar
trajectories in spatial networks", Journal of System and Software (Elsevier), vol. 82, no. 5,
pp. 772-788, May 2009.
In several applications, data objects move on pre-defined spatial networks such as road
segments, railways, and invisible air routes. Many of these objects exhibit similarity with
respect to their traversed paths, and therefore two objects can be correlated based on their
motion similarity. Useful information can be retrieved from these correlations and this
knowledge can be used to define similarity classes. In this paper, we study similarity search for
moving object trajectories in spatial networks. The problem poses some important challenges,
since it is quite different from the case where objects are allowed to move freely in any direction
without motion restrictions. New similarity measures should be employed to express similarity
between two trajectories that do not necessarily share any common sub-path. We define new
similarity measures based on spatial and temporal characteristics of trajectories, such that the
notion of similarity in space and time is well expressed, and moreover they satisfy the metric
properties. In addition, we demonstrate that similarity range queries in trajectories are efficiently
supported by utilizing metric-based access methods, such as M-trees.
J3. Eleftherios Tiakas, Apostolos N. Papadopoulos, Alexandros Nanopoulos, Yannis
Manolopoulos. "Node and edge selectivity estimation for range queries in spatial
networks", Information Systems (Elsevier), vol. 34, no. 3, pp. 328-352, May 2009.
Modern applications requiring spatial network processing pose several interesting query
optimization challenges. Spatial networks are usually represented as graphs, and therefore,
queries involving a spatial network can be executed by using the corresponding graph
representation. This means that the cost for executing a query is determined by graph properties
such as the graph order and size (i.e., number of nodes and edges) and other graph parameters.
In this paper, we present novel methods to estimate the number of nodes and edges in regions of
interest in spatial networks, towards predicting the space and time requirements for range
queries. The methods are evaluated by using real-life and synthetic data sets. Experimental
results show that the number of nodes and edges can be estimated efficiently and accurately,
with relatively small space requirements, thus providing useful information to the query
optimizer.
J4. Eleftherios Tiakas, Apostolos N. Papadopoulos, Yannis Manolopoulos. "Progressive
processing of subspace dominating queries", The VLDB Journal (Springer), vol. 20, no. 6,
pp. 921-948, December 2011.
A top-k dominating query reports the k items with the highest domination score. Algorithms for
efficient processing of this query have been recently proposed in the literature. Those methods,
either index based or index free, apply a series of pruning criteria toward efficient processing.
However, they are characterized by several limitations, such as (1) they lack progressiveness
(they report the k best items at the end of the processing), (2) they require a multi-dimensional
index or they build a grid-based index on-the-fly, which suffers from performance degradation,
especially in high dimensionalities, and (3) they do not support vertically decomposed data. In
this paper, we design efficient algorithms that can handle any subset of the dimensions in a
progressive manner. Among the studied algorithms, the Differential Algorithm shows the best
overall performance.
J5. Panagiotis Symeonidis, Eleftherios Tiakas, Yannis Manolopoulos. "A unified framework
for link and rating prediction in multi-modal social networks", International Journal of
Social Network Mining (Inderscience), vol. 1, no. 3/4, pp. 225-253, January 2013.
Multi-modal Social Networks (MSNs) allow users to form explicit (by adding new friends in
their network) or implicit (by similarly co-rating items) social networks. Previous research work
was limited either to the prediction of new relationships among users (i.e. Link Prediction
problem) or to the prediction of item ratings (i.e. Rating Prediction problem and Item
Recommendations). Recent link prediction methods infer future relationships among users, by
also exploiting information from their implicit networks (i.e. user-item rating network). On the
other hand, Rating Prediction methods predict the user’s rating behavior on items, by also
exploiting information from their explicit network (i.e. friendship network). In this paper, we
develop a framework to incorporate both research directions into a unified model. We extend
our Social-Union algorithm, which initially focused on the rating prediction problem, in order to
be applied also on the link prediction problem. Social-Union combines similarity matrices
derived from heterogeneous (unipartite and bipartite) explicit or implicit MSNs. Moreover, we
propose an effective weighting strategy of MSNs influence based on their structured density.
We also generalize our model for combining multiple social networks.We perform an extensive
experimental comparison of the proposed method against existing link and rating prediction
algorithms, using synthetic and two real data sets (Epinions and Flixter). Our experimental
results show that our Social-Union framework is more effective in both rating and link
prediction.
J6. Eleftherios Tiakas, Dimitrios Rafailidis, Anastasios Dimou, Petros Daras. "MSIDX: Multi-
Sort Indexing for Efficient Content-Based Image Search and Retrieval", Transactions on
Multimedia (IEEE), vol. 15, no. 6, pp. 1415-1430, October 2013.
In this paper, a novel approximate indexing scheme for efficient content-based image search and
retrieval is presented, called Multi-Sort Indexing (MSIDX). The proposed scheme analyzes high
dimensional image descriptor vectors, by employing the value cardinalities of their dimensions.
The dimensions' value cardinalities, an inherent characteristic of descriptor vectors, are the
number of discrete values in the dimensions. As expected, value cardinalities significantly vary,
due to the existence of several extraction methods. Moreover, different quantization and
normalization techniques used in the extraction process, have a strong impact on the dimensions'
value cardinalities. Since dimensions with high value cardinalities have more discriminative
power, a multiple sort algorithm is used to reorder the descriptors' dimensions according to their
value cardinalities, in order to increase the probability of two similar images to lie within a close
constant range. The expected bounds of the constant range are defined in detail, following
deterministic and probabilistic analyses. The proposed scheme is fully suitable (a) for real-time
indexing of images, and (b) for searching and retrieving relevant images with an efficient query
processing algorithm. In our experiments with five real datasets, we show the superiority of the
proposed approach against hashing methods, also suitable for approximate similarity search.
J7. Eleftherios Tiakas, Apostolos N. Papadopoulos, Yannis Manolopoulos. "On Estimating the
Maximum Domination Value and the Skyline Cardinality of Multi-Dimensional Data
Sets", International Journal of Knowledge-Based Organizations (IGI Global), vol. 3, no. 4,
pp. 61-83, October 2013.
The last years there is an increasing interest for query processing techniques that take into
consideration the dominance relationship between items to select the most promising ones,
based on user preferences. Skyline and top-k dominating queries are examples of such
techniques. A skyline query computes the items that are not dominated, whereas a top-k
dominating query returns the k items with the highest domination score. To enable query
optimization, it is important to estimate the expected number of skyline items as well as the
maximum domination value of an item. In this article, we provide an estimation for the
maximum domination value under the distinct values and attribute independence assumptions.
We provide three different methodologies for estimating and calculating the maximum
domination value and we test their performance and accuracy. Among the proposed estimation
methods, our method Estimation with Roots outperforms all others and returns the most accurate
results. We also introduce the eliminating dimension, i.e., the dimension beyond which all
domination values become zero, and we provide an efficient estimation of that dimension.
Moreover, we provide an accurate estimation of the skyline cardinality of a data set.
J8. Panagiotis Symeonidis, Eleftherios Tiakas. "Transitive node similarity: predicting and
recommending links in signed social networks", World Wide Web Journal (Springer), vol.
17, no. 4, pp. 743-776, July 2014.
Online social networks (OSNs) like Facebook, Myspace, and Hi5 have become popular,
because they allow users to easily share content. OSNs recommend new friends to registered
users based on local features of the graph (i.e., based on the number of common friends that two
users share). However, OSNs do not exploit the whole structure of the network. Instead, they
consider only pathways of maximum length 2 between a user and his candidate friends. On the
other hand, there are global approaches, which detect the overall path structure in a network,
being computationally prohibitive for huge-size social networks. In this paper, we define a basic
node similarity measure that captures effectively local graph features (i.e., by measuring
proximity between nodes). We exploit global graph features (i.e., by weighting paths that
connect two nodes) introducing transitive node similarity. We also derive variants of our
method that apply to different types of networks (directed/undirected and signed/unsigned). We
perform extensive experimental comparison of the proposed method against existing
recommendation algorithms using synthetic and real data sets (Facebook, Hi5 and Epinions).
Our experimental results show that our FriendTNS algorithm outperforms other approaches in
terms of accuracy and it is also time efficient. Finally, we show that a significant accuracy
improvement can be gained by using information about both positive and negative edges.
J9. Nantia Iakovidou, Eleftherios Tiakas, Konstantinos Tsichlas, Yannis Manolopoulos.
"Going over the three dimensional protein structure similarity problem", Artificial
Intelligence Review (Springer), vol. 42, no. 3, pp. 445-459, October 2014.
This article presents in detail our novel proposed methodology for detecting similarity between
or among three dimensional protein structures. The innovation of our algorithm relies on the
fact that during the similarity process, it has the ability to combine many attributes together and
fulfil lots of preconditions, which are extensively discussed throughout the paper. Our concept
is also supported by an efficient and effective indexing scheme, that provides convincing results
comparing to other known methods.
J10. Zaigham Faraz Siddiqui, Eleftherios Tiakas, Panagiotis Symeonidis, Myra
Spiliopoulou, Yannis Manolopoulos. "Learning Relational User Profiles and
Recommending Items as Their Preferences Change", International Journal on Artificial
Intelligence Tools (World Scientific Publishing Company), vol. 24, no. 2, 31 pages, April
2015.
Over the last decade a vast number of businesses have developed online e-shops in the web.
These online stores are supported by sophisticated systems that manage the products and record
the activity of customers. There exist many research works that strive to answer the question
“what items are the customers going to like” given their historical profiles. However, most of
these works do not take into account the time dimension and cannot respond efficiently when
data are huge. In this paper, we study the problem of recommendations in the context of multi-
relational stream mining. Our algorithm “xStreams” first separates customers based on their
historical data into clusters. It then employs collaborative filtering (CF) to recommend new
items to the customers based on their group similarity. To evaluate the working of xStreams, we
use a multi-relational data generator for streams. We evaluate xStreams on real and synthetic
datasets.
J11. Eleftherios Tiakas, George Valkanas, Apostolos N. Papadopoulos, Yannis
Manolopoulos, Dimitrios Gunopulos. "Processing Top-k Dominating Queries in Metric
Spaces", Transactions on Database Systems (ACM), vol. 40, no. 4, 38 pages, article 23,
January 2016.
Top-k dominating queries combine the natural idea of selecting the k best items with a
comprehensive “goodness” criterion based on dominance. A point p1 dominates p2 if p1 is as
good as p2 in all attributes and is strictly better in at least one. Existing works address the
problem in settings where data objects are multidimensional points. However, there are domains
where we only have access to the distance between two objects. In cases like these, attributes
reflect distances from a set of input objects and are dynamically generated as the input objects
change. Consequently, prior works from the literature can not be applied, despite the fact that
the dominance relation is still meaningful and valid. For this reason, in this work, we present the
first study for processing top-k dominating queries over distance-based dynamic attribute
vectors, defined over a metric space. We propose four progressive algorithms that utilize the
properties of the underlying metric space to efficiently solve the problem, and present an
extensive, comparative evaluation on both synthetic and real-world data sets.
J12. Dimitris Zianis, Gavriil Spyroglou, Eleftherios Tiakas, Kalliopi Radoglou. "Bayesian
and classical models to predict aboveground tree biomass allometry", Forest Science
Journal, vol. 62, no. 3, pp. 247-259, June 2016.
Total dry aboveground tree biomass (M) allometric equations were derived from 25
destructively sampled Hungarian oak (Quercus frainetto Ten.) trees, growing in Chalkidiki
peninsula (Northern Greece). The regression models were developed under Bayesian and
classical statistical approaches. All approaches captured equally well the variability in the
recorded M values across the diameter (D) range of the sampled trees. The Informative
Bayesian (IB) approach based on prior distributions about the allometric parameters and the size
dependent error variance provided quite accurate M predictions. Linear Regression (LR),
Nonlinear Regression (NLR) and Non-informative Bayesian (NB) approaches failed to predict
M distribution when validation was performed against an independent dataset previously
collected from the study area. It was concluded that adaptation of Bayesian theorem in tree
allometry research is strongly supported. A published simplified Bayesian approach, based on
six-tree sample, was applied in our dataset and is found to be a promising tool for allometric
relationships. Further research is needed in order to robustly support or reject such an approach.
Theoretical values of the slope in M-D allometry were validated against the derived parameter.
A number of scaling parameters may quite accurately describe tree biomass allometry, rather
than a unique pair of them.
Papers in Conference Proceedings
C1. Eleftherios Tiakas, Apostolos N. Papadopoulos, Alexandros Nanopoulos, Yannis
Manolopoulos, Dragan Stojanovic, Slobodanka Djordjevic-Kajan. "Trajectory Similarity
Search in Spatial Networks", Proceedings of the 10th International Database Engineering
& Applications Symposium (IEEE / IDEAS), pp. 185-192, Delhi, India, December 2006.
In several applications, data objects are assumed to move on predefined spatial networks such as
road segments, railways, invisible air routes. Moving objects may exhibit similarity with respect
to their traversed paths, and therefore two objects can be correlated based on their path
similarity. In this paper, we study similarity search for moving object trajectories for spatial
networks. The problem poses some important challenges, since it is quite different from the case
where objects are allowed to move without any motion restrictions. Experimental results
performed on real-life spatial networks show that trajectory similarity can be supported in an
effective and efficient manner by using metric-based access methods.
C2. Eletherios Tiakas, Stefanos Ougiaroglou, Petros Nicopolitidis. "Efficient broadcast disks
program construction in asymmetric communication environments", Proceedings of the
10th International Symposium on Modelling, Analysis and Simulation of Wireless and
Mobile Systems (ACM / MSWiM), pp. 279-283, Chania, Crete Island, Greece, October
2007.
A well-known technique for broadcast program construction is the Broadcast Disks. However, it
has important disadvantages, as for example that the broadcast program construction procedure
leaves some parts of the broadcast program empty. This paper proposes a new approach for the
construction of the broadcast program. Specifically, it presents three new algorithms, which face
the problems of the Broadcast Disk Technique. According to our approach, the broadcast
program is constructed with the minimum possible length, respecting the selected disk relative
frequencies and keeps the average delays of retrieving data-items low. The constructed
broadcast programs have no empty parts and retain their desired properties in any combination
of disk relative frequencies. Experimental results show that this approach is more efficient than
Broadcast Disks in all cases.
C3. Eleftherios Tiakas, Apostolos N. Papadopoulos, Alexandros Nanopoulos, Yannis
Manolopoulos. "Selectivity estimation in spatial networks", Proceedings of the 23rd
Annual Symposium on Applied Computing (ACM / SAC), pp. 852-856, Fortaleza, Ceara,
Brazil, March 2008.
Modern applications requiring spatial network processing pose many interesting query
optimization challenges. In many cases, query processing depends on the corresponding graph
size (number of nodes and edges) and other graph parameters. This dependency may be local or
global. In this paper, we present novel methods to estimate the number of nodes in regions of
interest in spatial networks, towards predicting the space and time requirements of range
queries. We examine all methods by using real-life and synthetic spatial networks. Experimental
results show that the number of nodes can be estimated efficiently and accurately with small
space requirements, thus providing useful information to the query optimizer.
C4. Eleftherios Tiakas, Apostolos N. Papadopoulos, Yannis Manolopoulos. "Graph Node
Clustering via Transitive Node Similarity", Proceedings of the 14th Panhellenic
Conference on Informatics (IEEE / PCI), pp. 72-77, Tripoli, Greece, September 2010.
This paper studies the problem of cluster detection in undirected graphs by using transitive node
similarity methods. Well-defined semi-metric measures are proposed to compute the similarity
between the nodes of the graph, and the clustering is based on the resulted similarity values. The
proposed algorithm has three major steps. In the first step, which is optional, a ranking of all the
nodes of the graph is performed by using application specific criteria (if any). In the second
step, a specific node is selected and the similarity values from this node to all other nodes are
computed and maintained into a similarity list. In the third step, from the resulted similarity list
values, the first cluster is constructed from the nodes that have a sufficient similarity score. The
last two steps, are repeated, until all the nodes of the graph have been clustered. This
methodology was tested in real-world data sets and provides promising clustering results. The
results of a representative real-word case of clustering nodes in a real road network are
presented and validated both numerically and visually.
C5. Eleftherios Tiakas, Apostolos N. Papadopoulos, Yannis Manolopoulos. "Estimation of the
Maximum Domination Value in Multi-dimensional Data Sets", Proceedings of the 14th
East-European Conference on Advances in Databases and Information Systems (Springer /
ADBIS), pp. 505-519, Novi Sad, Serbia, September 2010.
The last years there is an increasing interest for query processing techniques that take into
consideration the dominance relationship between objects to select the most promising ones,
based on user preferences. Skyline and top-k dominating queries are examples of such
techniques. A skyline query computes the objects that are not dominated, whereas a top-k
dominating query returns the k objects with the highest domination score. To enable query
optimization, it is important to estimate the expected number of skyline objects as well as the
maximum domination value of an object. In this paper, we provide an estimation for the
maximum domination value for data sets with statistical independence between their attributes.
We provide three different methodologies for estimating and calculating the maximum
domination value, and we test their performance and accuracy. Among the proposed estimation
methods, our method Estimation with Roots outperforms all others and returns the most accurate
results.
C6. Panagiotis Symeonidis, Eleftherios Tiakas, Yannis Manolopoulos. "Transitive node
similarity for link prediction in social networks with positive and negative links",
Proceedings of the 4th ACM Conference on Recommender Systems (ACM / RECSYS), pp.
183-190, Barcelona, Spain, September 2010.
Online social networks (OSNs) like Facebook, and Myspace recommend new friends to
registered users based on local features of the graph (i.e. based on the number of common
friends that two users share). However, OSNs do not exploit the whole structure of the network.
Instead, they consider only pathways of maximum length 2 between a user and his candidate
friends. On the other hand, there are global approaches, which detect the overall path structure
in a network, being computationally prohibitive for huge-size social networks. In this paper, we
define a basic node similarity measure that captures effectively local graph features. We also
exploit global graph features introducing transitive node similarity. Moreover, we derive
variants of our method that apply in signed networks. We perform extensive experimental
comparison of the proposed method against existing recommendation algorithms using synthetic
and real data sets (Facebook, Hi5 and Epinions). Our experimental results show that our
FriendTNS algorithm outperforms other approaches in terms of accuracy and it is also time
efficient. We show that a significant accuracy improvement can be gained by using information
about both positive and negative edges.
C7. Zaigham Faraz Siddiqui, Myra Spiliopoulou, Panagiotis Symeonidis, Eleftherios Tiakas.
"A Data Generator for Multi-Stream Data", Proceedings of the 2nd International
Workshop on Mining Ubiquitous and Social Environments (Springer / MUSE), pp. 63-70,
Athens, Greece, September 2011.
We present a stream data generator. The generator is mainly intended for multiple interrelated
streams, in particular for objects with temporal properties, which are fed by dependent streams.
Such data are e.g. customers their transactions: learning a model of the customers requires
considering the stream of their transactions. However, the generator can also be used for
conventional stream data, e.g. for learning the concepts of the transaction stream only. The
generator is appropriate for testing classification and clustering algorithms on concept discovery
and adaptation to concept drift. The number of concepts in the data can be specified as
parameter to the generator; the same holds for the membership of an instance to a class. Hence,
it is also appropriate for synthetic datasets on overlapping classes or clusters.
C8. Panagiotis Symeonidis, Eleftherios Tiakas, Yannis Manolopoulos. "Product
recommendation and rating prediction based on multi-modal social networks",
Proceedings of the 5th ACM Conference on Recommender Systems (ACM / RECSYS), pp.
61-68, Chicago, IL, USA, October 2011.
Online Social Rating Networks (SRNs) such as Epinions and Flixter, allow users to form
several implicit social networks, through their daily interactions like co-commenting on the
same products, or similarly co-rating products. The majority of earlier work in Rating Prediction
and Recommendation of products (e.g. Collaborative Filtering) mainly takes into account
ratings of users on products. However, in SRNs users can also built their explicit social network
by adding each other as friends. In this paper, we propose Social-Union, a method which
combines similarity matrices derived from heterogeneous (unipartite and bipartite) explicit or
implicit SRNs. Moreover, we propose an effective weighting strategy of SRNs influence based
on their structured density. We also generalize our model for combining multiple social
networks. We perform an extensive experimental comparison of the proposed method against
existing rating prediction and product recommendation algorithms, using synthetic and two real
data sets (Epinions and Flixter). Our experimental results show that our Social-Union algorithm
is more effective in predicting rating and recommending products in SRNs.
C9. Nantia Iakovidou, Eleftherios Tiakas, Konstantinos Tsichlas: "DISCO: A New Algorithm
for Detecting 3D Protein Structure Similarity", Proceedings of the Artificial Intelligence
Applications and Innovations Workshops (Springer / AIAI), pp. 622-631, Halkidiki, Greece,
September 2012.
Protein structure similarity is one of the most important aims pursued by bioinformatics and
structural biology, nowadays. Although quite a few similarity methods have been proposed
lately, yet fresh algorithms that fulfill new preconditions are needed to serve this purpose. In
this paper, we provide a new similarity measure for 3D protein structures that detects not only
similar structures but also similar substructures to a query protein, supporting both multiple and
pairwise comparison procedures and combining many comparison characteristics. In order to
handle similarity queries we utilize efficient and effective indexing techniques such as M-trees
and we provide interesting results using real, previously tested protein data sets.
C10. Eleftherios Tiakas, George Valkanas, Apostolos N. Papadopoulos, Yannis
Manolopoulos, Dimitrios Gunopulos: "Metric-Based Top-k Dominating Queries",
Proceedings of the 17th International Conference on Extending Database Technology
(Open Proceedings / EDBT), pp. 415-426, Athens, Greece, March 2014.
Top-k dominating queries combine the natural idea of selecting the k best items with a
comprehensive “goodness” criterion based on dominance. A point p1 dominates p2 if p1 is as
good as p2 in all attributes and is strictly better in at least one. Existing works address the
problem in settings where data objects are multidimensional points. However, there are domains
where we only have access to the distance between two objects. In cases like these, attributes
reflect distances from a set of input objects and are dynamically generated as the input objects
change. Consequently, prior works from the literature cannot be applied, despite the fact that the
dominance relation is still meaningful and valid. For this reason, in this work, we present the
first study for processing top-k dominating queries over distance-based dynamic attribute
vectors, defined over a metric space. We propose four progressive algorithms that utilize the
properties of the underlying metric space to efficiently solve the problem, and present an
extensive, comparative evaluation on both synthetic and real world data sets.
C11. Zaigham Faraz Siddiqui, Eleftherios Tiakas, Panagiotis Symeonidis, Myra
Spiliopoulou, Yannis Manolopoulos. "xStreams: Recommending Items to Users with
Time-evolving Preferences", Proceedings of the 4th International Conference on Web
Intelligence, Mining and Semantics (ACM / WIMS), Article 22, 12 pages, Thessaloniki,
Greece, June 2014.
Over the last decade a vast number of businesses have developed online e-shops in the web.
These online stores are supported by sophisticated systems that manage the products and record
the activity of customers. There exist many research works that strive to answer the question
"what items are the customers going to like" given their historic profiles. However, most of
these works miss to take into account the time dimension and cannot respond efficiently when
data are huge. In this paper, we study the problem of recommendations in the context of multi-
relational stream mining. Our algorithm first separates customers based on their historic data
into clusters. It then employs collaborative filtering (CF) to recommend new items to the
customers based on their clustering structure. We evaluate our algorithm on two data sets,
MovieLens and a synthetic data set.
C12. Eleftherios Tiakas, Apostolos N. Papadopoulos, Yannis Manolopoulos. "Top-k
Dominating Queries: a Survey (invited)", Proceedings of the 17th International
Symposium on Programming and Systems (ISPS), 10 pages, Algiers, Algeria, April 2015.
Top-k dominating queries combine the advantages of top-k queries and skyline queries, and
eliminate their disadvantages. They return k objects with the highest domination score, which is
defined as the number of dominated objects. As a top-k query, the user can bound the number
of returned results through the parameter k, and like a skyline query a user-selected scoring
function is not required. Top-k dominating queries have been studied by different perspectives,
such as in indexed and nonindexed multi-dimensional data using efficient exact computation
algorithms, in uncertain data using randomized algorithms with accuracy guarantees, and in
data streams. In addition, top-k dominating queries have been studied over distance-based
dynamic attribute vectors, defined over a metric space, using efficient progressive algorithms.
Top-k dominating queries have become an important tool for decision support, data mining,
web search, and multi-criteria retrieval applications.
C13. Eleftherios Tiakas, Apostolos N. Papadopoulos, Yannis Manolopoulos. "Skyline
Queries: an Introduction (invited)", Proceedings of the 6th International Conference on
Information, Intelligence, Systems & Applications (IISA), 6 pages, Corfu, Greece, July
2015.
During the two past decades, skyline queries were used in several multi-criteria decision
support applications. Given a dominance relationship in a dataset, a skyline query returns the
objects that cannot be dominated by any other objects. Skyline queries were studied extensively
in multidimensional spaces, in subspaces, in metric spaces, in dynamic spaces, in streaming
environments, and in time-series data. Several algorithms were proposed for skyline query
processing, such as window-based, progressive, distributed, geometric-based, index-based,
divide-and-conquer, and dynamic programming algorithms. Moreover, several variations were
proposed to solve application-specific problems like k-dominant skylines, top-k dominating
queries, spatial skyline queries, and others. As the number of objects that are returned in a
skyline query may become large, there is also an extensive study for the cardinality of skyline
queries. This extensive research depicts the importance of skyline queries and their variations
in modern applications.
C14. Eleftherios Tiakas, Dimitrios Rafailidis. "Scalable Trajectory Similarity Search Based
on Locations in Spatial Networks", Proceedings of the 5th International Conference on
Model and Data Engineering (Springer / MEDI), LNCS vol. 9344, pp. 213-224, Rhodes,
Greece, September 2015.
In this paper, we propose an efficient query processing algorithm that returns the trajectory
results in low search time. We limit the calculation of pairwise shortest path distances between
the set of query locations and the spatial nodes, by highly reducing the preprocessing
requirements. Also, we introduce a spatiotemporal similarity measure, based on which the
temporal-to-spatial significance of the trajectory results can be easily modified and the query
locations can be spatially prioritized according to users’ preferences. In our experiments with a
real-world road network, we show that the proposed method has approximately ten times less
preprocessing requirements than the competitive methods and reduces the search time by two
orders of magnitude at least.
C15. Alexander Tzanakas, Eleftherios Tiakas, Yannis Manolopoulos. "Skyline Algorithms
on Streams of Multidimensional Data", Proceedings of the 20th East-European Conference
on Advances in Databases and Information Systems (Springer / ADBIS), pp. 63-71, Prague,
Czech Republic, August 2016.
We compare three algorithms for skyline processing on streams of multidimensional data with
centralized processing, namely, the Look-Out, Lazy and Eager methods, with different dataset
types and dimensionalities, data cardinalities and sliding window sizes. Experimental results
for time performance and memory consumption are presented. In addition, the problem of
computing the exclusive dominance region in higher dimensions is reviewed and a novel
correct solution is proposed.
C16. Nikolaos Georgiadis, Eleftherios Tiakas, Yannis Manolopoulos. "Detecting Intrinsic
Dissimilarities in Large Image Databases through Skylines", Proceedings of the 9th
International Conference on Management of Digital EcoSystems (ACM / MEDES), pp.
194-201, Bangkok, Thailand, November 2017, [Best Paper Award].
In this paper we try to detect dissimilar images in image databases without defining a similarity
ranking function by capturing the intrinsic dissimilarities of image descriptor vectors. To this
end, we apply the skyline operation using their multi-dimensional descriptor vectors. We
implemented a number of skyline methods, combined with four hashing state-of-the-art
algorithms for data partitioning to create efficient indexing to secondary memory. We
compared and evaluated their results by using two real image datasets to measure the
performance and the effectiveness of the implemented algorithms. Detailed results show the
efficiency and effectiveness of our approach.
C17. Theodoros Tzouramanis, Eleftherios Tiakas, Apostolos N. Papadopoulos, Yannis
Manolopoulos. "The Range Skyline Query", Proceedings of the 27th International
Conference on Information and Knowledge Management (ACM / CIKM), pp. 47-56,
Torino, Italy, October 2018.
The range skyline query retrieves the dynamic skyline for every individual query point in a
range by generalizing the point-based dynamic skyline query. Its wide-ranging applications
enable users to submit their preferences within an interval of 'ideally sought' values across
every dimension, instead of being limited to submit their preference in relation to a single
sought value. This paper considers the query as a hyper-rectangle iso-oriented towards the axes
of the multi-dimensional space and proposes: (i) main-memory algorithmic strategies, which
are simple to implement and (ii) secondary-memory pruning mechanisms for processing range
skyline queries efficiently. The proposed approach is progressive and I/O optimal. A
performance evaluation of the proposed technique demonstrates its robustness and
practicability.
Book Chapters
CH1. Theodoros Semertzidis, Dimitrios Rafailidis, Eleftherios Tiakas, Michael G. Strintzis,
Petros Daras. "Multimedia Indexing, Search and Retrieval in Large Databases of Social
Networks", Social Media Retrieval, Computer Communications and Networks series
(Springer), pp. 43-63, 2012.
Social networks are changing the way multimedia content is shared on the Web, by allowing
users to upload their photos, videos, and audio content, produced by any means of digital
recorders such as mobile/smart-phones and Web/digital cameras. This plethora of content
created the need for finding the desired media in the social media universe. Moreover, the
diversity of the available content inspired users to demand and formulate more complicated
queries. In the social media era, multimedia content search is promoted to a fundamental feature
toward efficient search inside social multimedia streams, content classification, context and
event based indexing. In this chapter, an overview of multimedia indexing and searching
algorithms, following the data growth curve, is presented in detail. This chapter is thematically
structured in two parts. In the first part, pure multimedia content retrieval issues are presented,
while in the second part, the social aspects and new, interesting views on multimedia retrieval in
the large social media databases are discussed.
CH2. Gavriil Spyroglou, Eleftherios Tiakas, Gregor Chatziphilippidis, Vasiliki Kazana.
"The design and use of forest decision support systems in Greece", Computer-based tools
for supporting forest management. The experience and the expertise world-wide (Epsilon
Open Archive), pp. 152-167, 2014.
This paper presents the design and use of forest decision support systems in Greece. The
decision support systems were classified according to the methods and models that used for
their training, what technical knowledge management was used and what methods, if any, were
used for the contribution of participants and stakeholders. The decision support systems were
classified also as to the time horizon of their application: Long-term or strategic interest with a
horizon of 25 years, medium or regular interest with a horizon of 5-10 years, and short or
business interest with a horizon from one day to one year. Finally they were split between those
that take into account the spatial resolution and those who do not. In Greece there are 12
different forest decision support systems but which are personal efforts of researchers that
created them through several research programs. There is no clear Greek forest policy regarding
the use of such systems at headquarters and operational level.
Technical Reports
TR1. Alexander Tzanakas, Eleftherios Tiakas, Yannis Manolopoulos. "Revisited skyline
query algorithms on streams of multidimensional data", Technical Report, Aristotle
University of Thessaloniki, 2016.
This paper focuses on the analysis and evaluation of skyline query algorithms on streams of
multidimensional data. It presents three algorithms and evaluates them with different types of
datasets, number of dimensions and "Sliding Window" sizes. The results of these experiments
are reviewed according to time performance, memory consumption and the size of the skyline.
TR2. Nikolaos Pliakis, Eleftherios Tiakas, Yannis Manolopoulos. "Efficient Progressive
Processing of Trajectories on Road Networks", Technical Report, Aristotle University of
Thessaloniki, 2018.
The demand for efficient retrieval and query processing pertaining to trajectories in spatially
constrained networks (e.g., road networks, rivers/ports vessel monitoring, etc.) has caused an
increased research interest in the past decade, in both industry and academia. In this work, we
target the problem of efficient progressive evaluation of trajectories and we present a novel
methodology based on a variant of Cluster extended Adjacency List (CeAL). We also
investigate the applicability of the state-of-the-art access methods to efficiently retrieve
trajectories in spatial networks. Specifically, we examine FNR-trees [17] and MON-trees [11]
against our variation of the Cluster-extended Adjacency Lists (CeAL), which has been
designed for application in location-based trajectory similarity top-k queries, where the user
defines locations and time restrictions [40]. In addition: (1) we extend all the above access
methods to efficiently handle trajectories of objects that move through very large spatial
networks; and (2) to enhance their performance, we create an entirely new implementation
framework to generate trajectories and to test the trajectory retrieval for each approach. We
conducted extensive experimental evaluations which demonstrate that the comparisons between
R-tree-based methods are clearly in favour of MON-trees. Complementary to this, though, the
comparisons between R-tree-based methods and the proposed CeAL method show that the
latter structure prevails overall in space and time complexity. We also identify some open
issues that could further advance the present findings.
TR3. Nikolaos Georgiadis, Eleftherios Tiakas, Yannis Manolopoulos, Apostolos N.
Papadopoulos. "Skyline-based Dissimilarity of Images", Technical Report, Aristotle
University of Thessaloniki, 2019.
In this paper, we aim at capturing the intrinsic dissimilarities of image descriptors in large
image collections, i.e., to detect dissimilar (i.e., diverse) images without defining an explicit
similarity or distance function. To this end, we adopt skyline query processing techniques for
large image databases, based on their high-dimensional descriptor vectors. The novelty of the
proposed methodology lies in the use of skyline techniques empowered by state-of-the-art
hashing schemes to enable effective data partitioning and indexing in secondary memory,
towards supporting large image databases. The proposed approach is evaluated experimentally
by using three real-world image datasets. Performance evaluation results demonstrate that
images lying on the skyline have largely different characteristics, which depend on the type of
the descriptor. Thus, these skyline items can be used as seeds to apply clustering in large image
databases. In addition, we observe that skyline processing using hash-based indexing structures
is significantly faster than index-free skyline computation and also more efficient than skyline
computation with hierarchical indexing structures. Based on our results, the proposed approach
is both efficient (regarding runtime) and effective (with respect to image diversity) and
therefore can be used as a base for more complex data mining tasks such as clustering.