@article {853, title = {Cost-Efficient RSSI-Based Indoor Proximity Positioning, for Large/Complex Museum Exhibition Spaces}, journal = {Sensors}, volume = {25}, year = {2025}, pages = {2713}, abstract = {

RSSI-based proximity positioning is a well-established technique for indoor localization, featuring simplicity and cost-effectiveness, requiring low-price and off-the-shelf hardware. However, it suffers from low accuracy (in NLOS traffic), noise, and multipath fading issues. In large complex spaces, such as museums, where heavy visitor traffic is expected to seriously impact the ability to maintain LOS, RSSI coupled with Bluetooth Low Energy (BLE) seems ideal in terms of market availability, cost-/energy-efficiency and scalability that affect competing technologies, provided it achieves adequate accuracy. Our work reports and discusses findings of a BLE/RSSI-based pilot, implemented at the Museum of Modern Greek Culture in Athens, involving eight buildings with 47 halls with diverse areas, shapes, and showcase layouts. Wearable visitor BLE beacons provided cell-level location determined by a prototype tool (VTT), integrating in its architecture different functionalities: raw RSSI data smoothing with Kalman filters, hybrid positioning provision, temporal methods for visitor cell prediction, spatial filtering, and prediction based on popular machine learning classifiers. Visitor movement modeling, based on critical parameters influencing signal measurements, provided scenarios mapped to popular behavioral models. One such model, {\textquotedblleft}ant{\textquotedblright}, corresponding to relatively slow nomadic cell roaming, was selected for basic experimentation. Pilot implementation decisions and methods adopted at all layers of the VTT architecture followed the overall concept of simplicity, availability, and cost-efficiency, providing a maximum infrastructure cost of 8 Euro per m2 covered. A total 15 methods/algorithms were evaluated against prediction accuracy across 20 RSSI datasets, incorporating diverse hall cell allocations and visitor movement patterns. RSSI data, temporal and spatial management with simple low-processing methods adopted, achieved a maximum prediction accuracy average of 81.53\% across all datasets, while ML algorithms (Random Forest) achieved a maximum prediction accuracy average of 87.24\%.

}, keywords = {Bluetooth Low Energy, indoor proximity positioning, large/complex museums, machine learning classification, museum visitor modeling, RSSI temporal/spatial methods}, issn = {1424-8220}, doi = {https://doi.org/10.3390/s25092713}, url = {https://doi.org/10.3390/s25092713}, author = {Philippopoulos, Panos I. and Koutrakis, Kostas N. and Tsafaras, Efstathios D. and Papadopoulou, Evangelia G. and Sigalas, Dimitrios and Tselikas, Nikolaos D. and Ougiaroglou, Stefanos and Costas Vassilakis} } @conference {838, title = {Estimating MPdist with SAX and Machine Learning}, booktitle = {New Trends in Database and Information Systems (Proceedings of ADBIS 2024, Short Papers, Workshops, Doctoral Consortium and Tutorials)}, year = {2024}, publisher = {Springer Cham}, organization = {Springer Cham}, abstract = {

MPdist is a distance measure which considers two time series to be similar if they share many similar subsequences. However, computing MPdist can be slow, especially for large time series. We propose a technique for the approximate computation of MPdist that uses the SAX representation of the time series to quickly estimate the Nearest Neighbor (NN) distance of each subsequence, and then applies a Machine Learning model to correct the accuracy loss incurred. Our method is orders of magnitude faster than the exact computation of MPdist; at the same time, our best approximation computes the NN of a time series with high accuracy. A thorough evaluation of our technique is provided.

}, keywords = {Distance metric, Machine Learning, MPdist, Random Forest, SAX, Time series}, doi = {https://doi.org/10.1007/978-3-031-70421-5_32}, author = {Mihalis Tsoukalos and Pantelis Chronis and Nikos Platis and Costas Vassilakis}, editor = {Joe Tekli and Johann Gamper and Richard Chbeir and Yannis Manolopoulos and Salma Sassi and Mirjana Ivanovic and Vargas-Solar, Genoveva and Ester Zumpano} } @conference {826, title = {EnQuest: A Cloud Datalake Infrastructure for Heterogeneous Analytics in Maritime and Tourism Domains}, booktitle = {DATA 2023 (demo)}, year = {2023}, abstract = {

Within recent years, transportation and supply chain have been affected by an avalanche of data including IoT devices, online services, social media and others. However, the implemented solutions so far are fragmented, physically distributed, require specialized IT knowledge to deploy, and involve significant IT experience to operate even for trivial tasks. In the context of the ENIRISST+ project, we developed EnQuest1, an online data lake that allows users without any IT background to harvest, store, organize, analyze and share heterogeneous, multi-faceted maritime/tourism data. EnQuest provides a zero-administration, zero-cost, integrated framework that enables scientists, practitioners and other stakeholders within the above domains to easily: (i) deploy data acquisition services (crawlers, dataset imports, questionnaire forms), (ii) design and manage versatile customizable data stores, (iii) share whole datasets or horizontal/vertical data shards with other stakeholders, (iv) search, filter and analyze data via an expressive yet simple-to-use graphical query engine and visualization tools, and (v) perform user management and access control operations on the stored data. To the best of our knowledge, this is the first approach in the literature that targets users without an IT background and focuses on collecting, managing, analyzing, and sharing diverse, multi-faceted data in maritime the and tourism sectors. The main goals of the proposed demonstration are to showcase the EnQuest system to the conference participants and promote the work of the ENIRISST+ project consortium. During the demo we will (i) deploy social media crawlers to gather maritime data and show the participants how to process and visualise them, (ii) create live questionnaires using the EnQuest functionality, ask the participants to fill them in and demonstrate the live processed data on appropriate dashboards, and (iii) demonstrate how to import data and subscribe to data flows of other users through the implemented publish/subscribe module. For the needs of the demo we will only require internet connection and a desk; we will have our own laptops to use at the demonstration.

}, keywords = {big data, cloud systems, data analytics, datalakes, maritime, tourism}, author = {Kimon Deligiannis and Christos Tryfonopoulos and Paraskevi Raftopoulou and Nikos Platis and Costas Vassilakis} } @conference {825, title = {Estimating \iSAX Parameters for Efficiency}, booktitle = {Proceedings of the 27th European Conference on Advances in Databases and Information Systems (ADBIS 2023)}, year = {2023}, abstract = {

\iSAX is considered one of the most efficient indexes for time series. Several parameters affect the construction of an \iSAX index: the sliding window size, the threshold value, the number of segments and the maximum cardinality, the last two being related to the SAX representation. In this paper (i) we consider the effect of each parameter on the efficiency of the \iSAX index, (ii) we evaluate the importance of each parameter, and, (iii) suggest how to optimize these parameters.

}, keywords = {Indexing, Parameter tuning, SAX, Time series}, author = {Tsoukalos, Michalis and Platis, Nikos and Costas Vassilakis} } @conference {829, title = {Estimating \iSAX Parameters for Efficiency}, booktitle = {New Trends in Database and Information Systems (Proceedings of the 2023 European Conference on Advances in Databases and Information Systems / ADBIS 2023)}, year = {2023}, publisher = {Springer Nature Switzerland}, organization = {Springer Nature Switzerland}, address = {Cham}, abstract = {

\iSAX is considered one of the most efficient indexes for time series. Several parameters affect the construction of an \iSAX index: the sliding window size, the threshold value, the number of segments and the maximum cardinality, the last two being related to the SAX representation. In this paper (i) we consider the effect of each parameter on the efficiency of the \iSAX index, (ii) we evaluate the importance of each parameter, and, (iii) suggest how to optimize these parameters.

}, keywords = {Indexing, Parameter tuning, SAX, Time series}, isbn = {978-3-031-42941-5}, doi = {10.1007/978-3-031-42941-5_1}, author = {Tsoukalos, Michalis and Platis, Nikos and Costas Vassilakis} } @conference {821, title = {RoG: A Pipeline for Automated Sensitive Data Identification and Anonymisation}, booktitle = {Proceedings of the 2023 IEEE CSR Workshop on Data Science for Cyber Security (DS4CS)}, year = {2023}, abstract = {

Nowadays, the amount of data available online is constantly increasing. This data may contain sensitive or private information that can expose the person behind the data or be misused by malicious actors for identity theft, stalking, and other nefarious purposes. There is thus, a growing need to protect individuals{\textquoteright} privacy and prevent data breaches in several application domains. Protecting data privacy though, is a complex and multifaceted issue that involves a range of legal, ethical, and technical considerations. In this paper, we discuss the challenges associated with data protection, the role of automated tools, and the effectiveness of identifying and anonymising sensitive data. We then, propose a fully-automated process for sensitive data identification and anonymisation, based on Natural Language Processing (NLP) techniques, that can be applied both in big diverse datasets and to a wide range of domains.

}, keywords = {anonymisation, automated process, k-anonymity, NER, NLP, pipeline, sensitive/private data}, author = {Sotiris Nikoletos and Stefanos Vlachos and Efstathios Zaragkas and Costas Vassilakis and Christos Tryfonopoulos and Paraskevi Raftopoulou} } @conference {819, title = {SodaSense: An Intelligence Platform for Micro-Mobility, Micro-Climate and Agriculture}, booktitle = {Proceedings of the GEOProcessing 2023}, year = {2023}, abstract = {

SODASENSE is an end-to-end big data manipulation platform that focuses on decision and policy making. It concerns the management of big trajectory and spatio-temporal data that is collected from sensors and relates to micro-mobility, microclimate and agriculture, and aims to the creation of an expert decision making platform with research, social and business orientation.

}, keywords = {big data management and analysis, spatial time series, trajectories}, author = {Paraskevi Raftopoulou and Spiros Skiadopoulos and Christos Tryfonopoulos and Costas Vassilakis} } @article {811, title = {The Effects of Logistics Websites{\textquoteright} Technical Factors on the Optimization of Digital Marketing Strategies and Corporate Brand Name}, journal = {Processes}, volume = {10}, year = {2022}, month = {may}, pages = {892}, keywords = {advertising, big data, brand name, competitive advantage, digital marketing, logistics, predictive model, SEM, user engagement, web analytics}, doi = {https://doi.org/10.3390/pr10050892}, url = {https://www.mdpi.com/2227-9717/10/5/892}, author = {Damianos P. Sakas and Dimitrios P. Reklitis and Panagiotis Trivellas and Costas Vassilakis and Marina C. Terzi} } @article {817, title = {Multichannel Digital Marketing Optimizations through Big Data Analytics in the Tourism and Hospitality Industry}, journal = {Journal of Theoretical and Applied Electronic Commerce Research}, volume = {17}, year = {2022}, month = {oct}, pages = {1383{\textendash}1408}, abstract = {

The tourism sector increasingly relies on technology to acquire new clients in a world overflowing with information. So, the main question that needs to be answered is:What digital marketing strategy should be adopted to attract customers and built digital brand name by incorporating websites and social media big data? The authors of this research utilize web analytics and big data to build an innovative methodology in an effort to address this issue. After the data collection, statistical analysis was implemented, followed by a fuzzy cognitive map and an agent-based simulation model in order to illustrate the usage of social media and user experience in multichannel marketing. The findings suggest that, in contrast to the websites of other industries, such as logistics, where customers want to finish their inquiries as quickly as possible and leave the webpage, it is advantageous for tourism websites to keep customers{\textquoteright} attention moreon their website in order to increasevisibility. Additionally, the research further highlights the importance of personalization and user-engagement content to e-WOM, suggesting to tourism businesses to encourage posts made by customers and employees.

}, keywords = {advertising, big data, brand, digital marketing, e-WOM, hospitality, multichannel, social media, tourism, web analytics}, doi = {10.3390/jtaer17040070}, url = {https://www.mdpi.com/0718-1876/17/4/70}, author = {Damianos P. Sakas and Dimitrios P. Reklitis and Marina C. Terzi and Costas Vassilakis} } @mastersthesis {848, title = {Development and evaluation of a team formation algorithm for gaming environments}, year = {2021}, month = {10/2021}, pages = {48}, type = {Undergraduate}, abstract = {

In the context of multiplayer online games, but in many other group activities that entail collaboration between user, appropriate group formation is a critical issue. Groups should be formulated in a way that on the one hand user collaboration (or collaboration avoidance) preferences are respected, and on the other hand collaboration potential and productivity of groups is maximized.


In the current thesis, we consider an internet-based collaboration environment, where users work in pairs and, after their collaboration, each of them rates the quality of work and the quality of collaboration of his/her partner. Moreover, users have the option to express a positive, negative or neutral opinion towards the possibility of cooperating with individual users. For such an environment, we have developed an algorithm that employs linear
programming techniques, in order to create an optimal user pair formulation, considering the ratings that users have assigned to other users and collaboration intention statements. We present in detail the system structure, the algorithms and techniques employed, and we analyze the performance of the system in terms of the time needed to formulate user pair assignments
in various indicative cases. Finally, potential future extensions are outlined.

}, keywords = {glpk, Java, linear programming, maximization problem, scpsolver, User groups, μέθοδος simplex method}, author = {Iasonas Topalidis} } @article {772, title = {Hydria: An Online Data Lake for Multi-Faceted Analytics in the Cultural Heritage Domain}, journal = {Big Data and Cognitive Computing}, volume = {4}, year = {2020}, pages = {7}, abstract = {Advancements in cultural informatics have significantly influenced the way we perceive, analyze, communicate and understand culture. New data sources, such as social media, digitized cultural content, and Internet of Things (IoT) devices, have allowed us to enrich and customize the cultural experience, but at the same time have created an avalanche of new data that needs to be stored and appropriately managed in order to be of value. Although data management plays a central role in driving forward the cultural heritage domain, the solutions applied so far are fragmented, physically distributed, require specialized IT knowledge to deploy, and entail significant IT experience to operate even for trivial tasks. In this work, we present Hydria, an online data lake that allows users without any IT background to harvest, store, organize, analyze and share heterogeneous, multi-faceted cultural heritage data. Hydria provides a zero-administration, zero-cost, integrated framework that enables researchers, museum curators and other stakeholders within the cultural heritage domain to easily (i) deploy data acquisition services (like social media scrapers, focused web crawlers, dataset imports, questionnaire forms), (ii) design and manage versatile customizable data stores, (iii) share whole datasets or horizontal/vertical data shards with other stakeholders, (iv) search, filter and analyze data via an expressive yet simple-to-use graphical query engine and visualization tools, and (v) perform user management and access control operations on the stored data. To the best of our knowledge, this is the first solution in the literature that focuses on collecting, managing, analyzing, and sharing diverse, multi-faceted data in the cultural heritage domain and targets users without an IT background.}, keywords = {analytics and visualization, big data management, Cultural heritage, data lake, data store, open source}, doi = {10.3390/bdcc4020007}, url = {https://www.mdpi.com/2504-2289/4/2/7}, author = {Kimon Deligiannis and Paraskevi Raftopoulou and Christos Tryfonopoulos and Nikos Platis and Costas Vassilakis} } @conference {786, title = {Policy Making Analysis and Practitioner User Experience}, booktitle = {Proceedings of the 22nd International Conference on Human-Computer Interaction}, year = {2020}, publisher = {Springer International Publishing}, organization = {Springer International Publishing}, abstract = {

This article presents the work on social media analysis-driven policy-making platforms that are powered by classic social media analysis technologies, such as policy modelling, linguistic analysis, opinion mining, sentiment analysis and information visualization. The approach examines the user design perspective towards user experience in policymaking for all the innovative modules used. The technology behind such complex task is presented while the resulting platform is appraised on the potential for real world application. The findings drive the development and the requirements for the summative usability assessment tests. We also report on the level the practitioners adopted the policy formulation tools.

}, keywords = {Content Analysis, natural language interfaces, opinion mining, policy making, social network analysis, User Experience}, doi = {10.1007/978-3-030-60114-0_29}, author = {Dimitris Koryzis and Fotios Fitsilis and Dimitris Spiliotopoulos and Theocharis Theocharopoulos and Dionisis Margaris and Costas Vassilakis} } @conference {Theodoropoulos_2019_atmf, title = {ATMF: A student-centered framework for the effective implementation of alternative teaching methods for CSEd}, booktitle = {Proceedings of the Innovative Teaching of Introductory Topics in Information Technology - 3(IT) Workshop in the context of the 19th IFIP Conference on e-Business, e-Services and e-Society (I3E 2019)}, year = {2019}, month = {01/2020}, abstract = {

The dynamic development of Informatics introduces new educational and pedagogical challenges, including the instructional design of teaching and learning. How can we teach our students better in such a growing and demanding field? Moreover, how can we motivate them and together have better learning results? This paper aims to give answers to these questions, through a student-centered framework for effectively encompassing alternative teaching methods within CS. The proposed framework (ATMF) summarizes the benefits of alternative teaching methods in contrast with known is-sues of traditional teaching. In addition, ATMF is built upon empirical evidence and concludes that alternative practices, if used under the right conditions, can provide increased motivation for learning and better learning out-comes.

}, keywords = {Alternative Teaching Methods, Computer Science Education, Teaching Framework}, doi = {10.1007/978-3-030-39634-3_11}, author = {Anastasios Theodoropoulos and Costas Vassilakis and Angela Antoniou and Manolis Wallace and Giorgos Lepouras} } @article {589, title = {Efficient Continuous Multi-Query Processing over Graph Streams}, journal = {CoRR}, volume = {abs/1902.05134}, year = {2019}, url = {http://arxiv.org/abs/1902.05134}, author = {Lefteris Zervakis and Vinay Setty and Christos Tryfonopoulos and Katja Hose} } @conference {DBLP:conf/debs/ChantziosZST19, title = {Ping - A customizable, open-source information filtering system for textual data}, booktitle = {Proceedings of the 13th ACM International Conference on Distributed and Event-based Systems, DEBS 2019, Darmstadt, Germany, June 24-28, 2019.}, year = {2019}, pages = {228{\textendash}231}, doi = {10.1145/3328905.3332512}, url = {https://doi.org/10.1145/3328905.3332512}, author = {Thanasis Chantzios and Lefteris Zervakis and Spiros Skiadopoulos and Christos Tryfonopoulos} } @conference {588, title = {The quest for the appropriate cyber-threat intelligence sharing platform}, booktitle = {Proceedings of the 8th International Conference on Data Science, Technology and Applications (DATA), Prague, Czech Republic}, year = {2019}, month = { 07/2009}, abstract = {Cyber-threat intelligence (CTI) is any information that can help an organization identify, assess, monitor, and respond to cyber-threats. It relates to all cyber components of an organization such as networks, computers, and other types of information technology. In the recent years, due to the major increase of cyber-threats, CTI sharing is becoming increasingly important both as a subject of research and as a concept of providing additional security to organizations. However, selecting the proper tools and platforms for CTI sharing, is a challenging task, that pertains to a variety of aspects. In this paper, we start by overviewing the CTI procedure (threat types, categories, sources and the general CTI life-cycle). Then, we present a set of seven high-level CTI platform recommendations that can be used to evaluate a platform and subsequently we survey six state-of- the-art cyber-threat intelligence platforms. Finally, we compare and evaluate the six aforementioned platforms by means of the earlier proposed recommendations.}, keywords = {Cyber-threat, Intelligence, Sharing}, url = {http://users.uop.gr/~trifon/papers/pdf/data19-CKSKTBK.pdf}, author = {Thanasis Chantzios and Paris Koloveas and Spiros Skiadopoulos and Nikos Kolokotronis and Christos Tryfonopoulos and Vasiliki-Georgia Bilali and Dimitris Kavallieros} } @proceedings {590, title = {SciTo trends: visualising scientific topic trends}, year = {2019}, month = {September}, author = {Serafeim Chatzopoulos and Panagiotis Deligiannis and Thanasis Vergoulis and Ilias Kanellos and Christos Tryfonopoulos and Theodore Dalamagas} } @proceedings {DBLP:conf/pakdd/2018-2, title = {Advances in Knowledge Discovery and Data Mining - 22nd Pacific-Asia Conference, PAKDD 2018, Melbourne, VIC, Australia, June 3-6, 2018, Proceedings, Part II}, volume = {10938}, year = {2018}, publisher = {Springer}, isbn = {978-3-319-93036-7}, doi = {10.1007/978-3-319-93037-4}, url = {https://doi.org/10.1007/978-3-319-93037-4}, editor = {Dinh Q. Phung and Vincent S. Tseng and Geoffrey I. Webb and Bao Ho and Mohadeseh Ganji and Lida Rashidi} } @inbook {Vasilakis2018BigData, title = {Big Data Platforms and Applications}, year = {2018}, publisher = {Springer}, organization = {Springer}, chapter = {exhiSTORY: Smart self-organizing exhibits}, abstract = {Creating stories for exhibitions is a fascinating and in parallel laborious task. As every exhibition is designed to tell a story, museum curators are responsible for identifying, for each exhibit, its aspects that fit to the message of the story and position the exhibit at the right place in the story thread. In this context we analyze how the technological advances in the fields of sensors and Internet of Things can be utilized in order to construct a "smart space", which consists of self-organizing exhibits that cooperate with each other and provide visitors with comprehensible, rich, diverse, personalized and highly stimulating experiences. We present the system named "exhiSTORY" that intends to provide the appropriate infrastructure to be used in museums and places where exhibitions are held in order to support smart exhibits. The architecture of the system and its application potential is presented and discussed.}, author = {Costas Vassilakis and Vassilis Poulopoulos and Angela Antoniou and Manolis Wallace and Giorgos Lepouras and Martin Lopez Nores}, editor = {TBC} } @conference {545, title = {Data Science Tutor: An online platform for automated exercise solving in Data Science}, booktitle = {Proceedings of the 9th Conference on Computer Science Teaching (DIDINFO)}, year = {2018}, month = {October}, address = {Thessaloniki, Greece}, author = {Christos Tryfonopoulos and Charis Kotsiopoulos and Paraskevi Raftopoulou} } @conference {561, title = {The Effect of Introducing Content Price in Distributed Social Networks}, booktitle = {Proceedings of the 23rd Conference on Information Technologies (IT)}, year = {2018}, month = {March}, address = {Kaunas, Lithuania}, author = {Christos Tryfonopoulos} } @conference {578, title = {Efficient and Expressive Semantic Information Push for Cultural Heritage Applications}, booktitle = {Proceedings of the International Workshop on Semantic Web for Cultural Heritage (SW4CH @ ESWC)}, year = {2018}, month = {March}, address = {Crete, Greece}, author = {Christos Tryfonopoulos} } @conference {angelantEuromed18, title = {The Human Computer Interaction and Virtual Reality Lab (University of Peloponnese): overview and current challenges}, booktitle = {Proceedings of the {\textquotedblleft}Cultural informatics research and applications: State of the art and open challenges{\textquotedblright} workshop, within the Euromed 2018 Conference}, year = {2018}, month = {oct}, abstract = {The Human-Computer Interaction and Virtual Reality Lab, at the Department of Informatics and Telecommunications of the University of Peloponnese, aims to conduct high quality research in areas related to the analysis, design, develop-ment, and evaluation of HCI and VR systems and applications, and in parallel to support the teaching requirements of the department in the respective field. Over the last years the HCI-VR lab particularly focuses on Cultural Heritage and de-velops technologies primarily for spaces of cultural heritage that cover the diverse needs of heterogeneous audiences providing holistic visitor experience. The HCI-VR lab is actively participating in National and European projects on Cultural Heritage, such as FP7 Experimedia (https://hci-vr.dit.uop.gr/experimedia), H2020 CrossCult (www.crosscult.eu) and multiple projects from the National Strategic Reference Framework.}, url = {http://ceur-ws.org/Vol-2235/paper10.pdf}, author = {Angela Antoniou and Costas Vassilakis and Anastasios Theodoropoulos and Giorgos Lepouras} } @conference {558, title = {A Methodology for the Automatic Creation of Massive Continuous Query Datasets from Real-Life Corpora}, booktitle = {Proceedings of the 7th International Conference on Advanced Computer Science and Information Technology (ICAIT)}, year = {2018}, month = {April}, address = {Vienna, Austria}, author = {Christos Tryfonopoulos} } @article {Poulopoulos2018Heritage, title = {The personality of the influencers, the characteristics of qualitative discussions and their analysis for recommendations to cultural institutions}, journal = {Heritage}, volume = {1}, number = {2}, year = {2018}, month = {oct}, pages = {239-253}, abstract = {Social media usage is affecting peoples{\textquoteright} views through opinion sharing, a fact that has started to attract cultural institutions, as it is possible that this procedure can possibly be a part of a museum experience. As the main goal of a cultural institution is the maximization of senses stimulation, the device that is offered to the visitors{\textquoteright} hands everyday and every moment, becomes an important tool for the art spaces. In this notion we perform research on issues that can be of great importance for the museum{\textquoteright}s online presence and attraction. We focus on establishing the personality of influencers related to culture, as well as the characteristics of qualitative discussions on the social media. Crosscult Project is an EU funded project, that aims to spur a change in the way European citizens appraise History, and sets that basis of our research as the experiments are conducted within its scope of. Through the experimental procedure, we collect information in order to define the character of the influencer and the substances of a {\textquotedblleft}serious{\textquotedblright} conversation. {\textquotedblleft}Serious{\textquotedblright} conversations are regarded the ones in which a cultural organization can participate actively and benefit from the participation. We present the results of our experimental evaluation and analyze how cultural institutions can benefit from the outcomes of our research.}, keywords = {cultural informatics, digital humanities, personality traits, personalization, serious conversations, social media influencers, user modeling}, issn = {2571-9408}, doi = {10.3390/heritage1020016}, url = {https://doi.org/10.3390/heritage1020016}, author = {Vassilis Poulopoulos and Costas Vassilakis and Angela Antoniou and Giorgos Lepouras and Anastasios Theodoropoulos and Manolis Wallace} } @proceedings {DBLP:conf/gis/2018, title = {Proceedings of the 26th ACM SIGSPATIAL International Conference on Advances in Geographic Information Systems, SIGSPATIAL 2018, Seattle, WA, USA, November 06-09, 2018}, year = {2018}, publisher = {ACM}, isbn = {978-1-4503-5889-7}, url = {http://dl.acm.org/citation.cfm?id=3274895}, editor = {Farnoush Banaei Kashani and Erik G. Hoel and Ralf Hartmut G{\"u}ting and Roberto Tamassia and Li Xiong} } @article {DBLP:journals/tkde/TerrovitisPMS17, title = {Local Suppression and Splitting Techniques for Privacy Preserving Publication of Trajectories}, journal = {IEEE Trans. Knowl. Data Eng.}, volume = {29}, number = {7}, year = {2017}, pages = {1466{\textendash}1479}, doi = {10.1109/TKDE.2017.2675420}, url = {https://doi.org/10.1109/TKDE.2017.2675420}, author = {Manolis Terrovitis and Giorgos Poulis and Nikos Mamoulis and Spiros Skiadopoulos} } @conference {theodorakopoulos-smap2017, title = {Personalized Augmented Reality Experiences in Museums using Google Cardboards}, booktitle = {2017 12th International Workshop on Semantic and Social Media Adaptation and Personalization (SMAP)}, year = {2017}, month = {07}, publisher = {IEEE CPS}, organization = {IEEE CPS}, abstract = {In this short paper we examine the suitability of the Google Cardboard as a means for the delivery of personalized cultural experiences. Specifically, we develop the content and create the application required in order to provide highly personalized visits to the Archaeological Museum in Tripolis, Greece. We also examine the usability issues related to the use of Google Cardboards. Early results are promising, and based on them we also outline the next steps ahead.}, doi = {10.1109/smap.2017.8022676}, url = {https://ieeexplore.ieee.org/document/8022676/}, author = {Marinos Theodorakopoulos and Nikos Papageorgopoulos and Andriana Mourti and Angela Antoniou and Manolis Wallace and Giorgos Lepouras and Costas Vassilakis and Nikos Platis} } @proceedings {DBLP:conf/gis/2017, title = {Proceedings of the 25th ACM SIGSPATIAL International Conference on Advances in Geographic Information Systems, GIS 2017, Redondo Beach, CA, USA, November 7-10, 2017}, year = {2017}, publisher = {ACM}, isbn = {978-1-4503-5490-5}, url = {http://dl.acm.org/citation.cfm?id=3139958}, editor = {Erik G. Hoel and Shawn D. Newsam and Siva Ravada and Roberto Tamassia and Goce Trajcevski} } @article {581, title = {Query Reorganisation Algorithms for Efficient Boolean Information Filtering}, journal = {IEEE Transactions on Knowledge and Data Engineering}, volume = {29}, year = {2017}, pages = {418{\textendash}432}, abstract = {In the information filtering paradigm, clients subscribe to a server with continuous queries that express their information needs and get notified every time appropriate information is published. To perform this task in an efficient way, servers employ indexing schemes that support fast matches of the incoming information with the query database. Such indexing schemes involve (i) main-memory trie-based data structures that cluster similar queries by capturing common elements between them and (ii) efficient filtering mechanisms that exploit this clustering to achieve high throughput and low filtering times. However, state-of-the-art indexing schemes are sensitive to the query insertion order and cannot adopt to an evolving query workload, degrading the filtering performance over time. In this paper, we present an adaptive trie-based algorithm that outperforms current methods by relying on query statistics to reorganise the query database. Contrary to previous approaches, we show that the nature of the constructed tries, rather than their compactness, is the determining factor for efficient filtering performance. Our algorithm does not depend on the order of insertion of queries in the database, manages to cluster queries even when clustering possibilities are limited, and achieves more than 96\% filtering time improvement over its state-of-the-art competitors. Finally, we demonstrate that our solution is easily extensible to multi-core machines.}, keywords = {dissemination, indexing methods, Information filtering, user profiles and alert services}, doi = {10.1109/TKDE.2016.2620140}, url = {https://doi.org/10.1109/TKDE.2016.2620140}, author = {Lefteris Zervakis and Christos Tryfonopoulos and Spiros Skiadopoulos and Manolis Koubarakis} } @conference {591, title = {A crawler architecture for harvesting the clear, social, and dark web for IoT-related cyber-threat intelligence}, booktitle = {In Proceedings of the IEEE Workshop on Cyber Security \& Resilience in the Internet of Things (CSRIoT @ IEEE Services)}, year = {2016}, month = {July 2016}, publisher = {IEEE}, organization = {IEEE}, address = {Milan, Italy}, abstract = {The clear, social, and dark web have lately been identified as rich sources of valuable cyber-security information that {\textendash}given the appropriate tools and methods{\textendash} may be identified, crawled and subsequently leveraged to actionable cyber- threat intelligence. In this work, we focus on the information gathering task, and present a novel crawling architecture for transparently harvesting data from security websites in the clear web, security forums in the social web, and hacker fo- rums/marketplaces in the dark web. The proposed architecture adopts a two-phase approach to data harvesting. Initially a machine learning-based crawler is used to direct the harvesting towards websites of interest, while in the second phase state- of-the-art statistical language modelling techniques are used to represent the harvested information in a latent low-dimensional feature space and rank it based on its potential relevance to the task at hand. The proposed architecture is realised using exclusively open-source tools, and a preliminary evaluation with crowdsourced results demonstrates its effectiveness.}, keywords = {crawling architecture, cyber-security, cyber-threat intelligence, IoT, language models, Machine Learning}, url = {http://users.uop.gr/ trifon/papers/pdf/csriot19-KCTS.pdf}, author = {Paris Koloveas and Thanasis Chantzios and Christos Tryfonopoulos and Spiros Skiadopoulos} } @conference {DBLP:conf/esws/ZervakisTSK16, title = {Full-Text Support for Publish/Subscribe Ontology Systems}, booktitle = {The Semantic Web. Latest Advances and New Domains - 13th International Conference, ESWC 2016, Heraklion, Crete, Greece, May 29 - June 2, 2016, Proceedings}, year = {2016}, pages = {233{\textendash}249}, doi = {10.1007/978-3-319-34129-3_15}, url = {https://doi.org/10.1007/978-3-319-34129-3_15}, author = {Lefteris Zervakis and Christos Tryfonopoulos and Spiros Skiadopoulos and Manolis Koubarakis} } @conference {575, title = {R-Susceptibility: An IR-Centric Approach to Assessing Privacy Risks for Users in Online Communities}, booktitle = {Proceedings of the 39th Annual International ACM SIGIR Conference}, year = {2016}, month = {July}, address = {Pisa, Italy}, author = {Joanna Asia Biega and Krishna P. Gummadi and Ida Mele and Dragan Milchevski and Christos Tryfonopoulos and Gerhard Weikum} } @conference {DBLP:conf/edbt/ZervakisTSSS16, title = {Towards Publish/Subscribe Functionality on Graphs}, booktitle = {Proceedings of the Workshops of the EDBT/ICDT 2016 Joint Conference, EDBT/ICDT Workshops 2016, Bordeaux, France, March 15, 2016.}, year = {2016}, url = {http://ceur-ws.org/Vol-1558/paper13.pdf}, author = {Lefteris Zervakis and Christos Tryfonopoulos and Vinay Setty and Stephan Seufert and Spiros Skiadopoulos} } @conference {563, title = {Cloud-Based Data and Knowledge Management for Multi-Centre Biomedical Studies}, booktitle = {Proceedings of the International Conference on Knowledge Capture (K-CAP)}, year = {2015}, month = {October 7-10}, address = {Palisades NY, USA}, abstract = {Among the basic research tools for (bio)medical science are epidemiological studies that typically involve a number of hospitals, clinics, and research centres scattered around the world, and are often referred to as multi-centre studies. Clearly, the effectiveness and importance of a multi-centre study increases with the number of participating centres and enrolled patients, but at the same time this natural distribution in the production of research data requires sophisticated data management infrastructures to support the participating units. This kind of infrastructure is not only expensive to build and maintain, but also cannot be reused as it is often tailored to a specific study. In this work, we present a cloud-based system, coined CLOUDSTUDY, that allows users without any computer science background to design, deploy, and administer platforms aimed for managing, sharing, and analysing clinical data from multi-centre studies. The CLOUDSTUDY system provides a zero-administration, zero-cost online tool for creating multi- centre studies that (i) enhances re-usability by introducing study templates, (ii) supports (bio)medical needs through specialised data types, and (iii) emphasises data filtering/export through an expressive yet simple graphical query engine.}, doi = {10.1145/2815833.2816949}, url = {https://doi.org/10.1145/2815833.2816949}, author = {Amalia Tsafara and Christos Tryfonopoulos and Spiros Skiadopoulos and Lefteris Zervakis} } @conference {DBLP:conf/kcap/TsafaraTSZ15, title = {Cloud-Based Data and Knowledge Management for Multi-Centre Biomedical Studies}, booktitle = {Proceedings of the 8th International Conference on Knowledge Capture, K-CAP 2015, Palisades, NY, USA, October 7-10, 2015}, year = {2015}, pages = {24:1{\textendash}24:4}, doi = {10.1145/2815833.2816949}, url = {https://doi.org/10.1145/2815833.2816949}, author = {Amalia Tsafara and Christos Tryfonopoulos and Spiros Skiadopoulos and Lefteris Zervakis} } @conference {570, title = {Constructing Subsumption Hierarchies of Web Queries}, booktitle = {Proceedings of the International Workshop on Dataset PROFIling and fEderated Search for Linked Data (PROFILES @ ESWC)}, year = {2015}, month = {May}, address = {Portoroz, Slovenia}, author = {Alexander Prohaska and Christos Tryfonopoulos and Georgiana Ifrim} } @article {katifori15a, title = {Effectiveness of visualization for information retrieval through ontologies with entity evolution: the impact of ontology modeling}, journal = {International Journal of Information Retrieval Research}, volume = {5}, number = {2}, year = {2015}, pages = {26}, abstract = {Incorporating digital tools in the business and scientific research workflows is at the moment an on-going process, challenging and demanding as every domain has its own needs in terms of data models and information retrieval methods. The information in some domains involves entity evolution, a characteristic that introduces additional tasks, such as finding all evolution stages of an entity, and poses additional requirements for the information retrieval process. In this paper, we present a user study aiming to investigate how the different aspects of ontology modelling affect the performance and effectiveness of users regarding information retrieval tasks that are carried out using visualization methods. The results of the user study are analyzed and guidelines for ontology design are offered.}, doi = {10.4018/IJIRR.2015040104}, author = {Akrivi Katifori and Costas Vassilakis and Giorgos Lepouras and Elena Torou} } @conference {kmas15, title = {A mobile-enabled platform for presenting and disseminating cultural heritage information enhanced with augmented reality (Greek title: ΜΙΑ ΠΛΑΤΦΟΡΜΑ ΓΙΑ ΠΑΡΟΥΣΙΑΣΗ ΚΑΙ ΔΙΑΧΥΣΗ ΠΛΗΡΟΦΟΡΙΩΝ ΠΟΛΙΤΙΣΤΙΚΗΣ ΚΛΗΡΟΝΟΜΙΑΣ ΜΕ ΥΠΟΣΤΗΡΙΞΗ ΓΙΑ ΚΙΝΗΤΕΣ ΣΥΣΚΕΥΕΣ ΚΑΙ ΕΜΠ}, booktitle = {1st Panhellenic Conference on Cultural Heritage Digitization}, year = {2015}, month = {9}, abstract = {The advent of mobile technologies has created opportunities for more effective delivery of cultural heritage information to all interested parties, and especially tourists who are on-the-move. Many people nowadays are equipped with smartphones or tablets equipped with location tracking devices such as GPS and compasses and having internet access available; these smartphones can be used for efficient delivery of cultural heritage information, in a personalized and timely fashion. Moreover, the computing resources of these smartphones are adequate to enable the use of augmented reality techniques, which provide a lively and engaging experience to the users. However, the same content still needs to be disseminated to users of stationary computers. In this paper, we report on the design and development of a mobile-enabled platform for presenting and disseminating cultural heritage information enhanced with augmented reality and integration with social networks.}, author = {K. Μασσέλος and Costas Vassilakis and Giorgos Lepouras and Christos Tryfonopoulos and Ν. Τσελίκας and Nikos Platis} } @conference {556, title = {A Platform for the Presentation and Dissemination of Cultural Heritage Information for Mobile Devices Enriched with Augmented Reality}, booktitle = {Proceedings of the Greek Conference for the Digitization of Cultural Information (EUROMED)}, year = {2015}, month = {September}, address = {Volos, Greece}, author = {K. Masselos and Costas Vassilakis and Giorgos Lepouras and Christos Tryfonopoulos and N. Tselikas and N. Platis} } @conference {aamas15-GPT, title = {PViz: Visualising P2P Multi-Agent Simulations}, booktitle = {Proceedings of the International Conference on Autonomous Agents and Multiagent Systems (AAMAS)}, year = {2015}, month = {May}, pages = {1945{\textendash}1946}, address = {Istanbul, Turkey}, author = {Dimitris Giouroukis and Nikos Platis and Christos Tryfonopoulos} } @inbook {565, title = {SECRETA: A Tool for Anonymizing Relational, Transaction and RT-Datasets}, booktitle = {Medical Data Privacy Handbook}, year = {2015}, pages = {83-109}, publisher = {Springer}, organization = {Springer}, author = {Giorgos Poulis and Aris Gkoulalas-Divanis and Grigorios Loukides and Spiros Skiadopoulos and Christos Tryfonopoulos}, editor = {Aris Gkoulalas-Divanis and Grigorios Loukides} } @inbook {DBLP:books/sp/15/PoulisGLST15, title = {SECRETA: A Tool for Anonymizing Relational, Transaction and RT-Datasets}, booktitle = {Medical Data Privacy Handbook}, year = {2015}, pages = {83{\textendash}109}, doi = {10.1007/978-3-319-23633-9_5}, url = {https://doi.org/10.1007/978-3-319-23633-9_5}, author = {Giorgos Poulis and Aris Gkoulalas-Divanis and Grigorios Loukides and Spiros Skiadopoulos and Christos Tryfonopoulos} } @conference {541, title = {Towards Content-Based Publish/Subscribe for Distributed Social Networks}, booktitle = {Proceedings of the International Conference on Distributed Event-Based Systems (DEBS)}, year = {2015}, month = {June}, address = {Oslo, Norway}, author = {Christos Tryfonopoulos and Paraskevi Raftopoulou and Vinay Setty and Argiris Xiros} } @article {582, title = {Distributed Large-Scale Information Filtering}, journal = {Transactions on Large-Scale Data- and Knowledge-Centered Systems (TLDKS)}, volume = {13}, year = {2014}, pages = {91{\textendash}122}, abstract = {We study the problem of distributed resource sharing in peer-to-peer networks and focus on the problem of information filter- ing. In our setting, subscriptions and publications are specified using an expressive attribute-value representation that supports both the Boolean and Vector Space models. We use an extension of the distributed hash table Chord to organise the nodes and store user subscriptions, and utilise efficient publication protocols that keep the network traffic and latency low at filtering time. To verify our approach, we evaluate the proposed protocols experimentally using thousands of nodes, millions of user subscriptions, and two different real-life corpora. We also study three important facets of the load-balancing problem in such a scenario and present a novel algorithm that manages to distribute the load evenly among the nodes. Our results show that the designed protocols are scalable and efficient: they achieve expressive information filtering functionality with low message traffic and latency.}, keywords = {distributed hash tables, Information management, publish/subscribe}, author = {Christos Tryfonopoulos and Stratos Idreos and Manolis Koubarakis and Paraskevi Raftopoulou} } @conference {Rompa2014, title = {Mindmap-Inspired Semantic Personal Information Management}, booktitle = {Demo at the 17th International Conference on Extending Database Technology, 2014, Athens, Greece}, year = {2014}, month = {3/2014}, abstract = {Users nowadays need to manage large amounts of information, including documents, e-mails, contacts, and multimedia content. To facilitate the tasks of organisation, maintenance, and retrieval of personal information, a number of semantics-based methods have emerged; these methods employ (personal) ontologies as an underlying infrastructure for organising and querying the personal information space. In this paper we present OntoFM, a novel personal information management tool that offers a mindmap-inspired interface to facilitate user interactions with the information base. Besides serving as an information retrieval aid, OntoFM allows the user to specify and update the semantic links between information items, constituting thus a complete personal information management tool.}, doi = {10.5441/002/edbt.2014.55}, url = {http://dx.doi.org/10.5441/002/edbt.2014.55}, author = {Rompa, J. and Christos Tryfonopoulos and Costas Vassilakis and Giorgos Lepouras} } @conference {553, title = {Mindmap-Inspired Semantic Personal Information Management}, booktitle = {Proceedings of the 17th International Conference on Extending Database Technology (EDBT)}, year = {2014}, month = {March}, address = {Athens, Greece}, author = {Jenny Rompa and Christos Tryfonopoulos and Costas Vassilakis and Giorgos Lepouras} } @conference {DBLP:conf/edbt/PoulisGLST14, title = {SECRETA: A System for Evaluating and Comparing RElational and Transaction Anonymization algorithms}, booktitle = {Proceedings of the 17th International Conference on Extending Database Technology, EDBT 2014, Athens, Greece}, year = {2014}, month = {March 24-28}, pages = {620{\textendash}623}, doi = {10.5441/002/edbt.2014.58}, url = {https://doi.org/10.5441/002/edbt.2014.58}, author = {Giorgos Poulis and Aris Gkoulalas-Divanis and Grigorios Loukides and Spiros Skiadopoulos and Christos Tryfonopoulos} } @proceedings {DBLP:conf/icdm/2013w, title = {13th IEEE International Conference on Data Mining Workshops, ICDM Workshops, TX, USA, December 7-10, 2013}, year = {2013}, publisher = {IEEE Computer Society}, isbn = {978-0-7695-5109-8}, url = {http://ieeexplore.ieee.org/xpl/mostRecentIssue.jsp?punumber=6732242}, editor = {Wei Ding and Takashi Washio and Hui Xiong and George Karypis and Bhavani M. Thuraisingham and Diane J. Cook and Xindong Wu} } @conference {DBLP:conf/bibe/TsafaraTS13, title = {CloudStudy: A cloud-based system for supporting multi-centre studies}, booktitle = {13th IEEE International Conference on BioInformatics and BioEngineering, BIBE 2013, Chania, Greece, November 10-13, 2013}, year = {2013}, pages = {1{\textendash}4}, doi = {10.1109/BIBE.2013.6701549}, url = {https://doi.org/10.1109/BIBE.2013.6701549}, author = {Amalia Tsafara and Christos Tryfonopoulos and Spiros Skiadopoulos} } @conference {550, title = {DS4: A Distributed Social and Semantic Search System}, booktitle = {Proceedings of 35th European Conference on Information Retrieval (ECIR)}, year = {2013}, month = {March}, address = {Moscow, Russia}, author = {Dionisis Kontominas and Paraskevi Raftopoulou and Christos Tryfonopoulos and E.G.M. Petrakis} } @conference {539, title = {DS4: Introducing Semantic Friendship in Distributed Social Networks.}, booktitle = {Proceedings of the 21st International Conference on Cooperative Information Systems (CoopIS)}, year = {2013}, month = {September}, address = {Graz, Austria}, author = {Paraskevi Raftopoulou and Christos Tryfonopoulos and E.G.M. Petrakis and Nikos Zevlis} } @article {DBLP:journals/corr/ZervakisTPKS13, title = {Full-text Support for Publish/Subscribe Ontology Systems}, journal = {CoRR}, volume = {abs/1307.2015}, year = {2013}, url = {http://arxiv.org/abs/1307.2015}, author = {Lefteris Zervakis and Christos Tryfonopoulos and Antonios Papadakis-Pesaresi and Manolis Koubarakis and Spiros Skiadopoulos} } @conference {masie2013, title = {Improving museum visitors{\textquoteright} Quality of Experience through intelligent recommendations: A visiting style-based approach}, booktitle = {Proceedings of MASIE 2013 Workshop, co-located with the 9th International Conference on Intelligent Environments IE{\textquoteright}13}, year = {2013}, month = {7}, address = {Athens, GR}, abstract = {This paper investigates the effect that smart routing and recommendations can have on improving the Quality of Experience of museum visitors. The novelty of our approach consists of taking into account not only user interests but also their visiting styles, as well as modeling the museum not as a sterile space but as a location where crowds meet and interact, impacting each visitor?s Quality of Experience. The investigation is done by an empirical study on data gathered by a custom-made simulator tailored for the museum user routing problem. Results are promising and future potential and directions are discussed.}, doi = {10.3233/978-1-61499-286-8-507}, author = {Ioanna Lykourentzou and Claude, X. and Y. Naudet and Tobias, E. and Angela Antoniou and Giorgos Lepouras and Costas Vassilakis} } @conference {gala2013, title = {User Profiling: Towards a Facebook Game that Reveals Cognitive Style}, booktitle = {Proceedings of the GALA 2013 conference}, year = {2013}, month = {10}, pages = {349{\textendash}353}, address = {Paris, FR}, abstract = {This paper presents an innovative approach based on social-network gaming, which will extract players? cognitive styles for personalization purposes. Cognitive styles describe the way individuals think, perceive and remember information and can be exploited to personalize user interaction. Questionnaires are usually employed to identify cognitive styles, a tedious process for most users. Our approach relies on a Facebook game for discovering potential visitors? cognitive styles with an ultimate goal of enhancing the overall visitors{\textquoteright} experience in the museum. By hosting such a game on the museum?s webpage and on Facebook, the museum aims to attract new visitors, as well as to support the user profiling process.}, doi = {10.1007/978-3-319-12157-4_28}, author = {Angela Antoniou and Ioanna Lykourentzou and Rompa, J. and Tobias, E. and Giorgos Lepouras and Costas Vassilakis and Y. Naudet} } @conference {554, title = {Full-text Support for Publish/Subscribe Ontology Systems}, booktitle = {Proceedings of the Extended Semantic Web Conference (ESWC)}, year = {2012}, month = {May}, address = {Crete, Greece}, author = {Lefteris Zervakis and Christos Tryfonopoulos and Antonios Papadakis-Pesaresi and Manolis Koubarakis and Spiros Skiadopoulos} } @article {DBLP:journals/corr/abs-1207-0135, title = {Privacy Preservation by Disassociation}, journal = {CoRR}, volume = {abs/1207.0135}, year = {2012}, url = {http://arxiv.org/abs/1207.0135}, author = {Manolis Terrovitis and John Liagouris and Nikos Mamoulis and Spiros Skiadopoulos} } @article {DBLP:journals/pvldb/TerrovitisLMS12, title = {Privacy Preservation by Disassociation}, journal = {PVLDB}, volume = {5}, number = {10}, year = {2012}, pages = {944{\textendash}955}, doi = {10.14778/2336664.2336668}, url = {http://vldb.org/pvldb/vol5/p944_manolisterrovitis_vldb2012.pdf}, author = {Manolis Terrovitis and John Liagouris and Nikos Mamoulis and Spiros Skiadopoulos} } @conference {560, title = {OntoFM: A Personal Ontology-based File Manager for the Desktop}, booktitle = {Proccedings of the International Semantic Web Conference (ISWC)}, year = {2011}, month = {October}, address = {Bonn, Germany}, author = {Jenny Rompa and Giorgos Lepouras and Costas Vassilakis and Christos Tryfonopoulos} } @conference {Rompa2011, title = {OntoFM: A Personal Ontology-based File Manager for the Desktop}, booktitle = {Demo at the 10th International Web Conference, 2011, Bonn, Germany}, year = {2011}, month = {10}, abstract = {OntoFM is a novel file manager that bases its interactivity on the user?s personal ontology, offering semantic browsing and searching mechanisms for locating files, a mind map inspired ontology visualization, and simple-to-use intuitive functionality that encourages less experienced users. The implementation of OntoFM is based on Protege, an extensible open source ontology editor and knowledge-base framework. The file manager is implemented as a Protege tab widget, retrieving information from your personal ontology. Ontology visualization is based upon the OntoGraf plug-in which has been extended to comply with the mind map paradigm. Currently the ontology visualization pane permits only navigational functions, while other ontology management functions have been hidden to ease the complexity of the user interface.}, url = {https://arxiv.org/abs/1307.2018}, author = {Rompa, J. and Giorgos Lepouras and Costas Vassilakis and Christos Tryfonopoulos} } @conference {538, title = {Pricing Information Goods in Distributed Agent-based Information Filtering}, booktitle = {Proceedings of the 19th International Conference on Cooperative Information Systems (CoopIS)}, year = {2011}, month = {October}, address = {Crete, Greece}, author = {Christos Tryfonopoulos and Laura Maria Andreescu} } @article {dix2010b, title = {From the web of data to a world of action}, journal = {Journal of Web Semantics}, volume = {8 issue 4}, year = {2010}, pages = {394-408}, abstract = {This paper takes as its premise that the web is a place of action, not just information, and that the purpose of global data is to serve human needs. The paper presents several component technologies, which together work towards a vision where many small micro-applications can be threaded together using automated assistance to enable a unified and rich interaction. These technologies include data detector technology to enable any text to become a start point of semantic interaction; annotations for web-based services so that they can link data to potential actions; spreading activation over personal ontologies, to allow modelling of context; algorithms for automatically inferring {\textquoteleft}typing{\textquoteright} of web-form input data based on previous user inputs; and early work on inferring task structures from action traces. Some of these have already been integrated within an experimental web-based (extended) bookmarking tool, Snip!t, and a prototype desktop application On Time, and the paper discusses how the components could be more fully, yet more openly, linked in terms of both architecture and interaction. As well as contributing to the goal of an action and activity-focused web, the work also exposes a number of broader issues, theoretical, practical, social and economic, for the Semantic Web.}, doi = {10.1016/j.websem.2010.04.007}, author = {Alan Dix and Giorgos Lepouras and Akrivi Katifori and Costas Vassilakis and Tiziana Catarci and Antonella Poggi and Yannis Ioannidis and Miguel Morae and I. Daradimos and Nazihah Md.Akima and Shah Rukh Humayound and Fabio Terella} } @article {torou2010, title = {Historical research in archives: user methodology and supporting tools}, journal = {International Journal on Digital Libraries}, volume = {11(1)}, year = {2010}, pages = {25{\textendash}36}, abstract = {Historic research involves finding, using, and correlating informationwithin primary and secondary sources, in order to communicate an understanding of past events. In this process, historians employ their scientific knowledge, experience, and intuition to formulate queries (who was involved in an event, when did an event occur etc.), and subsequently try to locate the pertinent information from their sources. In this article, the authors investigate how historians formulate queries, which query terms are chosen, and how historians proceed in searching for related information in sources. The insight gained from this investigation can be subsequently used for organizing documentswithin historical source repositories and building tools that will enable historians to access the needed informationmore rapidly and fully.}, doi = {10.1007/s00799-010-0062-4}, author = {Elena Torou and Akrivi Katifori and Costas Vassilakis and Giorgos Lepouras and C. Halatsis} } @article {DBLP:journals/tkde/ClementiniSBT10, title = {A Reasoning System of Ternary Projective Relations}, journal = {IEEE Trans. Knowl. Data Eng.}, volume = {22}, number = {2}, year = {2010}, pages = {161{\textendash}178}, doi = {10.1109/TKDE.2009.79}, url = {https://doi.org/10.1109/TKDE.2009.79}, author = {Eliseo Clementini and Spiros Skiadopoulos and Roland Billen and Francesco Tarquini} } @conference {537, title = {Anonymity and Censorship Resistance in Unstructured Overlay Networks}, booktitle = {Proceedings of the 17th International Conference on Cooperative Information Systems (CoopIS)}, year = {2009}, month = {November}, address = {Vilamoura, Portugal}, author = {Michael Backes and Marek Hamerlik and Alessandro Linari and Matteo Maffei and Christos Tryfonopoulos and Gerhard Weikum} } @conference {torou2009a, title = {Capturing the historical research methodology: an experimental approach}, booktitle = {Proceedings of International Conference of Education, Research and Innovation (ICERI 2009)}, year = {2009}, month = {11}, abstract = {This paper presents the results of a study on how historians conduct research in a historical archive, and the methodologies they use while searching. Historic research involves finding, using, interpreting and correlating information within primary and secondary sources, in order to understand past events. The collection of historical data is accomplished through methodical and comprehensive research in primary and secondary sources. An important factor in our study was to understand what kind of data and/or information historians are looking for in a library/historical archive, either printed or digitized, and which research methodologies or research models they use while they investigate a historical archive. Since this issue has not been addressed insofar, and therefore there are no methods for elucidating research methodologies or research models that historians employ / use, we formulated a questionnaire comprising of seven information retrieval tasks commonly addressed in the context of historic research. History researchers were asked to describe in detail how they would proceed in searching for the information they need for completing these tasks. Through this procedure we aimed to investigate the different ways a historian can use to tackle a specific question, examine whether there exists a common research methodology, and the historic researchers? expectations and preferences. The insight gained from this investigation can be used for educational purposes, since it could be useful in the creation / development of a methodology for conducting research on historical information. Furthermore, the findings can be exploited in the context of organizing documents within historical source repositories, so as to facilitate the retrieval of documents by historians; finally the presented findings can serve as a preliminary requirement analysis phase for building tools that will enable historians to access more rapidly and fully the information they need.}, author = {Elena Torou and Akrivi Katifori and Costas Vassilakis and Giorgos Lepouras and C. Halatsis} } @conference {562, title = {EverLast: A Distributed Architecture for Preserving the Web}, booktitle = {Proceedings of the Joint Conference on Digital Libraries (JCDL)}, year = {2009}, month = {June}, address = {Austin, Texas}, author = {Avishek Anand and Srikanta Bedathur and Klaus Berberich and Ralf Schenkel and Christos Tryfonopoulos} } @article {583, title = {Information Filtering and Query Indexing for an Information Retrieval Model}, journal = {ACM Transactions on Information Systems (TOIS)}, volume = {27}, year = {2009}, pages = {1{\textendash}47}, author = {Christos Tryfonopoulos and Manolis Koubarakis and Yannis Drougas} } @article {540, title = {Rewiring Strategies for Semantic Overlay Networks}, journal = {Distributed and Parallel Databases (DAPD)}, volume = {26}, year = {2009}, pages = {181{\textendash}205}, abstract = {Semantic overlay networks cluster peers that are semantically, thematically or socially close into groups, by means of a rewiring procedure that is periodically executed by each peer. This procedure establishes new connections to similar peers and disregards connections to peers that are dissimilar. Retrieval effectiveness is then improved by exploiting this information at query time (as queries may address clusters of similar peers). Although all systems based on semantic overlay networks apply some rewiring technique, there is no comprehensive study showing the effect of rewiring on system{\textquoteright}s performance. In this work, a framework for studying the attribution of rewiring strategies in semantic overlay networks is proposed. A generic approach to rewiring is presented and several variants of this approach are reviewed and evaluated. We show how peer organisation is affected by the different design choices of the rewiring mechanism and how these choices affect the performance of the system overall (both in terms of communication overhead and retrieval effectiveness). Our experimental evaluation with real-word data and queries confirms the dependence between rewiring strategies and retrieval performance, and gives insights on the trade-offs involved in the selection of a rewiring strategy.}, keywords = {Information retrieval, peer-to-peer networks, rewiring strategies, semantic overlay networks}, author = {Paraskevi Raftopoulou and E.G.M. Petrakis and Christos Tryfonopoulos} } @article {lep2008a1, title = {An active blackboard for service discovery, composition and execution}, journal = {International Journal of Electronic Governance}, volume = {1}, number = {3}, year = {2008}, pages = {275 - 295}, publisher = {Inderscience Publishers}, abstract = {Organisations are turning to customer-centric electronic services, oriented to servicing customers{\textquoteright} life-events. This development requires methods for automatically locating and synthesising individual services to compose complex ones that will service the customer{\textquoteright}s life-events, since manual composition, either at the customer or the organisation side, incurs functional, economic and technical problems. In this paper we present an active blackboard architecture, which automates the task of service composition based on the semantics of individual services and data dependencies between them. The blackboard incorporates registries, which facilitate service discovery and an execution engine that arranges for dynamic service composition and execution.}, keywords = {blackboard architecture, e-government, e-services, electronic governance, electronic services, ontologies, semantics, service composition}, doi = {10.1504/IJEG.2008.020450}, author = {Giorgos Lepouras and Costas Vassilakis and Anya Sotiropoulou and Dimitrios Theotokis and Akrivi Katifori} } @booklet {569, title = {Anonymous and Censorship-resistant Content-sharing in Unstructured Overlays}, year = {2008}, author = {Michael Backes and Marek Hamerlik and Alessandro Linari and Matteo Maffei and Christos Tryfonopoulos and Gerhard Weikum} } @conference {586, title = {Approximate Information Filtering in Peer-to-Peer Networks}, booktitle = {Proceedings of the 9th Web Information Systems Engineering (WISE) Conference}, year = {2008}, month = {September}, address = {Auckland, New Zealand}, author = {Christian Zimmer and Christos Tryfonopoulos and Klaus Berberich and Manolis Koubarakis and Gerhard Weikum} } @conference {574, title = {Exploiting Correlated Keywords to Improve Approximate Information Filtering}, booktitle = {Proceedings of the 31st Annual International ACM SIGIR Conference}, year = {2008}, month = {July}, address = {Singapore}, author = {Christian Zimmer and Christos Tryfonopoulos and Gerhard Weikum} } @conference {549, title = {Information Retrieval and Filtering over Self-Organising Digital Libraries}, booktitle = {Proceedings of the 12th European Conference on Research and Advanced Technology for Digital Libraries (ECDL)}, year = {2008}, month = {September}, address = {Aarhus, Denmark}, author = {Paraskevi Raftopoulou and E.G.M. Petrakis and Christos Tryfonopoulos and Gerhard Weikum} } @conference {566, title = {P2P Information Retrieval and Filtering with MAPS}, booktitle = {Proccedings of the IEEE International Conference on Peer-to-Peer Computing (P2P)}, year = {2008}, month = {September}, address = {Aachen, Germany}, author = {Christian Zimmer and Johannes Heinz and Christos Tryfonopoulos and Gerhard Weikum} } @conference {Katifori2008133, title = {Selected results of a comparative study of four ontology visualization methods for information retrieval tasks}, booktitle = {Proceedings of the 2nd International Conference on Research Challenges in Information Science, RCIS 2008}, year = {2008}, note = {cited By (since 1996) 0}, month = {6}, pages = {133-140}, abstract = {The need for effective ontology visualization for design, management and browsing has arisen as a result of the progress in the areas of Semantic Web and Personal Information Management. There are several ontology visualizations available through existing ontology management tools, but not as many evaluations to determine their advantages and disadvantages and their suitability for various ontologies and user groups. This work presents selected results of an evaluation of four visualization methods in ProtΓ{\textcopyright}gΓ{\textcopyright}.}, keywords = {Communication, Comparative studies, Information management, Information retrieval, Information science, Information services, Information theory, Management, Management information systems, Ontology, Ontology managements, Personal Information managements, Semantic Web, Telecommunication services, User groups, User interfaces, Visualization, visualization methods}, doi = {10.1109/RCIS.2008.4632101}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-57349172797\&partnerID=40\&md5=1f36a9a0febecb929cd7904c84004143}, author = {Akrivi Katifori and Elena Torou and Costas Vassilakis and Giorgos Lepouras and C. Halatsis} } @conference {Katifori200832, title = {Supporting research in historical archives: Historical information visualization and modeling requirements}, booktitle = {Proceedings of the International Conference on Information Visualisation}, year = {2008}, note = {cited By (since 1996) 0}, month = {7}, pages = {32-37}, abstract = {The on-going progress in the area of digital libraries has lead to the beginning of a digitization effort in Historical Archives, as well. The requirements of historical research, which works with histories of entities and incomplete information, create the need for supplementary tools to support users in handling the digitized content. This work is based on a user study of historian information retrieval methods in order to create a set of tools for the context of historical archives, which will facilitate historical data storage, management and visualization. Β{\textcopyright} 2008 IEEE.}, keywords = {Data visualization, Digital libraries, Heuristics, Historical archive, Information analysis, Information management, Information retrieval, Information science, Information services, Information systems, International conferences, Libraries, Ontology, Search engines, Visualization}, doi = {10.1109/IV.2008.70}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-51749114860\&partnerID=40\&md5=a5b3e7f74314d5651816424c11e6cbc1}, author = {Akrivi Katifori and Elena Torou and Costas Vassilakis and C. Halatsis} } @article {557, title = {Architectural Alternatives for Information Filtering in Structured Overlay Networks}, journal = {IEEE Internet Computing}, volume = {11}, year = {2007}, pages = {24-34}, author = {Christos Tryfonopoulos and Christian Zimmer and Manolis Koubarakis and Gerhard Weikum} } @conference {543, title = {Efficient Search and Approximate Information Filtering in a Distributed Peer-to-Peer Environment of Digital Libraries}, booktitle = {Proceedings of the DELOS Conference on Digital Libraries}, year = {2007}, month = {February}, address = {Pisa, Italy}, author = {Christian Zimmer and Christos Tryfonopoulos and Gerhard Weikum} } @conference {KatiforiVTLHD07, title = {Historical Archive Ontologies Requirements, Modeling and Visualization}, booktitle = {RCIS}, year = {2007}, month = {4}, pages = {401-406}, abstract = {Most ontology development methodologies and tools for ontology management deal with ontology snapshots, i.e. they model and manage only the most recent version of ontologies, which is inadequate for contexts where the history of the ontology is of interest, such as historical archives. This work presents a set of requirements for the modeling and visualization of a temporal ontology used as a tool for the representation of historical information. In accordance to these requirements, a visualization plug-in was designed and implemented, featuring a set of tools that enable users to efficiently examine ontology temporal characteristics such as class and instance evolution along the timeline.}, author = {Akrivi Katifori and Costas Vassilakis and Elena Torou and Giorgos Lepouras and C. Halatsis and I. Daradimos} } @conference {548, title = {MinervaDL: An Architecture for Information Retrieval and Filtering in Distributed Digital Libraries}, booktitle = {Proceedings of the 11th European Conference on Research and Advanced Technology for Digital Libraries (ECDL)}, year = {2007}, month = {September}, address = {Budapest, Hungary}, author = {Christian Zimmer and Christos Tryfonopoulos and Gerhard Weikum} } @article {DBLP:journals/dke/TerrovitisVSBCMR07, title = {Modeling and language support for the management of pattern-bases}, journal = {Data Knowl. Eng.}, volume = {62}, number = {2}, year = {2007}, pages = {368{\textendash}397}, doi = {10.1016/j.datak.2006.10.002}, url = {https://doi.org/10.1016/j.datak.2006.10.002}, author = {Manolis Terrovitis and Panos Vassiliadis and Spiros Skiadopoulos and Elisa Bertino and Barbara Catania and Anna Maddalena and Stefano Rizzi} } @conference {564, title = {Node Behavior Prediction for Large-Scale Approximate Information Filtering}, booktitle = {Proceedings of the International Workshop on Large-Scale Distributed Systems for Information Retrieval (LSDS-IR @ SIGIR)}, year = {2007}, month = {July}, address = {Amsterdam, The Netherlands}, author = {Christian Zimmer and Christos Tryfonopoulos and Klaus Berberich and Gerhard Weikum and Manolis Koubarakis} } @conference {1154709, title = {A Comparative Study of Four Ontology Visualization Techniques in Protege: Experiment Setup and Preliminary Results}, booktitle = {IV {\textquoteright}06: Proceedings of the conference on Information Visualization}, year = {2006}, month = {7}, pages = {417{\textendash}423}, publisher = {IEEE Computer Society}, organization = {IEEE Computer Society}, address = {Washington, DC, USA}, abstract = {The continuing need for more effective information retrieval has lead to the creation of the notions of the semantic web and personalized information management, areas of study that very often employ ontologies to represent the semantic context of a domain. Consequently, the need for effective ontology visualization for design, management and browsing has arisen. There are several ontology visualizations available through the existing ontology management tools, but not as many evaluations to determine their advantages and disadvantages and their suitability for various ontologies and user groups. This work presents the preliminary results of an evaluation of four visualization methods in Protege.}, isbn = {0-7695-2602-0}, doi = {10.1109/IV.2006.3}, author = {Akrivi Katifori and Elena Torou and C. Halatsis and Giorgos Lepouras and Costas Vassilakis} } @conference {DBLP:conf/icdim/TorouKVLH06, title = {Creating an Historical Archive Ontology: Guidelines and Evaluation}, booktitle = {ICDIM}, year = {2006}, month = {12}, pages = {102-109}, abstract = {Ontologies have been proven invaluable tools both for the semantic web and for personal information management. In the context of a historical archive an ontology may provide meaningful and efficient support for search tasks as well as be used as a tool for storage and presentation of historical data. The creation however of such an ontology is complex, since the digitized archive documents are not in text format and the concepts that must be captured may vary among different time periods. This work presents a user-centric methodological approach for extracting the ontology of an historical archive focusing on the evaluation issues related to this process. The approach is exemplified through cases from its application in the University of Athens Historical Archive.}, doi = {10.1109/ICDIM.2007.369337}, author = {Elena Torou and Akrivi Katifori and Costas Vassilakis and Giorgos Lepouras and C. Halatsis} } @conference {559, title = {Distributed Evaluation of Continuous Equi-join Queries over Large Structured Overlay Networks}, booktitle = {Proceedings of the 22nd International Conference on Data Engineering (ICDE)}, year = {2006}, month = {April}, address = {Atlanda, USA}, author = {Stratos Idreos and Christos Tryfonopoulos and Manolis Koubarakis} } @inbook {lep2006a, title = {Encyclopedia of E-Commerce, E-Government and Mobile Commerce}, year = {2006}, pages = {1064{\textendash}1069}, publisher = {Idea Group Inc.}, organization = {Idea Group Inc.}, chapter = {Tailorable e-government information systems}, abstract = {Real-world information, knowledge and procedures after which information systems are modeled are generally of dynamic nature and subject to changes, due to the emergence of new requirements or revisions to initial specifications. E-government information systems (eGIS) present a higher degree of volatility in their environment, since requirement changes may stem from multiple sources, including legislation changes, organizational reforms, end-user needs, interoperability and distribution concerns etc. To this end, the design and implementation of eGIS must adhere to paradigms and practices that facilitate the accommodation of changes to the eGIS as they occur in the real world. In this work, we present a role-based model for designing and implementing eGIS that can dynamically accomodate changes, providing the necessary facilities for modeling multiple aspects of the same real-world entities and delivering context-specific behaviour.}, doi = {10.4018/978-1-59140-799-7.ch171}, author = {Giorgos Lepouras and Anya Sotiropoulou and Dimitrios Theotokis and Costas Vassilakis}, editor = {Mehdi Khosrow-Pour} } @article {DBLP:journals/tkde/KoubarakisST06, title = {Logic and Computational Complexity for Boolean Information Retrieval}, journal = {IEEE Trans. Knowl. Data Eng.}, volume = {18}, number = {12}, year = {2006}, pages = {1659{\textendash}1666}, doi = {10.1109/TKDE.2006.193}, url = {https://doi.org/10.1109/TKDE.2006.193}, author = {Manolis Koubarakis and Spiros Skiadopoulos and Christos Tryfonopoulos} } @conference {adpuc06-BKTWZ, title = {MAPS: Approximate Publish/Subscribe Functionality in Peer-to-Peer Networks}, booktitle = {Proceedings of Advanced Data Processing in Ubiquitous Computing Workshop (ADPUC @ Middleware)}, year = {2006}, month = {November}, pages = {1{\textendash}6}, address = {Melbourne, Australia}, author = {Klaus Berberich and Manolis Koubarakis and Christos Tryfonopoulos and Gerhard Weikum and Christian Zimmer} } @conference {Lepouras2005573, title = {An active ontology-based blackboard architecture for Web service interoperability}, booktitle = {2005 International Conference on Services Systems and Services Management, Proceedings of ICSSSM{\textquoteright}05}, volume = {1}, year = {2005}, note = {cited By (since 1996) 1}, month = {6}, pages = {573-578}, abstract = {Web services are functional, independent components that can be called over the web to perform a task. Web services are provided by organizations to enable others to perform tasks the organization offers online. However, with an ever increasing number of web services, finding the web service that performs a certain task is not always easy. Furthermore, adopting an end-user point of view what is needed is the actual result and not the service per se. It is often the case that more than one service have to be combined to produce the anticipated outcome, e.g. in the case of life-events. To this end, we propose an active, ontology-based blackboard architecture that aims at tackling the problems inherent in dynamic synthesis of composite web services and at facilitating user interaction with complex e-government transactions. Β{\textcopyright} 2005 IEEE.}, keywords = {Active blackboard architecture, Computer architecture, Electronic commerce, Interoperability, Ontology-based architecture, Web service synthesis, World Wide Web}, doi = {10.1109/ICSSSM.2005.1499537}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-33745256434\&partnerID=40\&md5=d1cd6446d2f3bc9ed098036d2f2bd384}, author = {Giorgos Lepouras and Costas Vassilakis and Anya Sotiropoulou and Dimitrios Theotokis and Akrivi Katifori} } @conference {vassilakis05b, title = {A Blackboard-oriented Architecture for e-Government service composition}, booktitle = {Proceedings of the IRMA 2005 conference}, year = {2005}, month = {5}, abstract = {A requirement for electronic government initiatives to succeed is the ability to offer a citizen-centric view of the government model. The most widely adopted paradigm supporting this task is the life event model, which combines basic services offered from multiple public authorities into a single, high-level service that corresponds to an event in a citizen{\textquoteright}s life. This composition is not always straightforward though, because the constituent services are generally developed in an independent fashion, using incompatible input and output formats; moreover the task of synchronising the documents required and produced by the services is tedious to implement and costly to maintain, since changes to requirements and legislation necessitate continuous updates to this scheme. In this paper, we present a blackboard architecture that can be used to deliver life-event oriented services to the citizens. The blackboard proposed for this architecture is an active one, undertaking the tasks of conversions, where appropriate. The blackboard couples a data flow approach with event-condition-action rules to enable dynamic formulation of life-event services, decentralising their development and maintenance.}, author = {Costas Vassilakis and Anya Sotiropoulou and Dimitrios Theotokis and D. Gouscos} } @conference {DBLP:conf/er/VassiliadisSTS05, title = {Blueprints and Measures for ETL Workflows}, booktitle = {Conceptual Modeling - ER 2005, 24th International Conference on Conceptual Modeling, Klagenfurt, Austria, October 24-28, 2005, Proceedings}, year = {2005}, pages = {385{\textendash}400}, doi = {10.1007/11568322_25}, url = {https://doi.org/10.1007/11568322_25}, author = {Panos Vassiliadis and Alkis Simitsis and Manolis Terrovitis and Spiros Skiadopoulos} } @proceedings {DBLP:conf/dawak/2005, title = {Data Warehousing and Knowledge Discovery, 7th International Conference, DaWaK 2005, Copenhagen, Denmark, August 22-26, 2005, Proceedings}, volume = {3589}, year = {2005}, publisher = {Springer}, isbn = {3-540-28558-X}, doi = {10.1007/11546849}, url = {https://doi.org/10.1007/11546849}, editor = {A Min Tjoa and Juan Trujillo} } @article {593, title = {Fair Resource Allocation in a Simple Multi-Agent Setting: Search Algorithms and Experimental Evaluation}, journal = {International Journal on Artificial Intelligence Tools (IJAIT)}, volume = {14}, year = {2005}, month = {December}, pages = {887{\textendash}899}, abstract = {We study the problem of fair resource allocation in a simple cooperative multi-agent setting where we have k agents and a set of n objects to be allocated to those agents. Each object is associated with a weight represented by a positive integer or real number. We would like to allocate all objects to the agents so that each object is allocated to only one agent and the weight is distributed fairly. We adopt the fairness index popularized by the networking community as our measure of fairness, and study centralized algorithms for fair resource allocation. Based on the relationship between our problem and number partitioning, we devise a greedy algorithm for fair resource allocation that runs in polynomial time but is not guaranteed to find the optimal solution, and a complete anytime algorithm that finds the optimal solution but runs in exponential time. Then we study the phase transition behavior of the complete algorithm. Finally, we demonstrate that the greedy algorithm actually performs very well and returns almost perfectly fair allocations.}, keywords = {Fairness; resource allocation; number partitioning; phase transitions}, author = {Paraskevi Raftopoulou and Manolis Koubarakis and Kostas Stergiou and Peter Triantafillou} } @article {DBLP:journals/is/VassiliadisSGTS05, title = {A generic and customizable framework for the design of ETL scenarios}, journal = {Inf. Syst.}, volume = {30}, number = {7}, year = {2005}, pages = {492{\textendash}525}, doi = {10.1016/j.is.2004.11.002}, url = {https://doi.org/10.1016/j.is.2004.11.002}, author = {Panos Vassiliadis and Alkis Simitsis and Panos Georgantas and Manolis Terrovitis and Spiros Skiadopoulos} } @conference {DBLP:conf/dawak/SimitsisVTS05, title = {Graph-Based Modeling of ETL Activities with Multi-level Transformations and Updates}, booktitle = {Data Warehousing and Knowledge Discovery, 7th International Conference, DaWaK 2005, Copenhagen, Denmark, August 22-26, 2005, Proceedings}, year = {2005}, pages = {43{\textendash}52}, doi = {10.1007/11546849_5}, url = {https://doi.org/10.1007/11546849_5}, author = {Alkis Simitsis and Panos Vassiliadis and Manolis Terrovitis and Spiros Skiadopoulos} } @conference {547, title = {LibraRing: An Architecture for Distributed Digital Libraries Based on DHTs}, booktitle = {Proceedings of the 9th European Conference on Research and Advanced Technology for Digital Libraries (ECDL)}, year = {2005}, month = {September}, address = {Vienna, Austria}, author = {Christos Tryfonopoulos and Stratos Idreos and Manolis Koubarakis} } @conference {542, title = {Publish/Subscribe Functionalities for Future Digital Libraries using Structured Overlay Networks}, booktitle = {Proceedings of the 8th International Workshop of the DELOS Network of Excellence on Digital Libraries on Future Digital Library Management Systems}, year = {2005}, month = {March}, address = {Schloss Dagstuhl, Germany}, author = {Christos Tryfonopoulos and Stratos Idreos and Manolis Koubarakis} } @conference {573, title = {Publish/Subscribe Functionality in IR Environments using Structured Overlay Networks}, booktitle = {Proceedings of the 28th Annual International ACM SIGIR Conference}, year = {2005}, month = {August}, address = {Salvador, Brazil}, author = {Christos Tryfonopoulos and Stratos Idreos and Manolis Koubarakis} } @conference {571, title = {Distributed Resource Sharing using Self-Organized Peer-to-Peer Networks and Languages from Information Retrieval}, booktitle = {Proceedings of the International Workshop on Self-* Properties in Complex Information Systems (Self-*)}, year = {2004}, month = {May}, address = {Bertinoro, Italy}, author = {Christos Tryfonopoulos and Manolis Koubarakis} } @conference {568, title = {Implementing Publish/Subscribe Systems with Languages from Information Retrieval on Top of Structured Overlay Networks}, booktitle = {Proceedings of the International Workshop on Peer-to-Peer and IR (P2P\&IR @ SIGIR)}, year = {2004}, month = {July}, address = {Sheffield, UK}, author = {Christos Tryfonopoulos and Manolis Koubarakis} } @conference {DBLP:conf/ssdbm/TerrovitisVSBCM04, title = {Modeling and Language Support for the Management of Pattern-Bases}, booktitle = {Proceedings of the 16th International Conference on Scientific and Statistical Database Management (SSDBM 2004), 21-23 June 2004, Santorini Island, Greece}, year = {2004}, pages = {265{\textendash}274}, doi = {10.1109/SSDBM.2004.54}, url = {http://doi.ieeecomputersociety.org/10.1109/SSDBM.2004.54}, author = {Manolis Terrovitis and Panos Vassiliadis and Spiros Skiadopoulos and Elisa Bertino and Barbara Catania and Anna Maddalena} } @conference {576, title = {P2P-DIET: An Extensible P2P Service that Unifies Ad-hoc and Continuous Querying in Super-Peer Networks}, booktitle = {Proceedings of the ACM SIGMOD Conference}, year = {2004}, month = {June}, address = {Paris, France}, author = {Stratos Idreos and Manolis Koubarakis and Christos Tryfonopoulos} } @conference {551, title = {P2P-DIET: One-Time and Continuous Queries in Super-Peer Networks}, booktitle = {Proceedings of the 9th International Conference on Extending Database Technology (EDBT)}, year = {2004}, month = {March}, address = {Heraklion, Greece}, author = {Stratos Idreos and Manolis Koubarakis and Christos Tryfonopoulos} } @conference {585, title = {Publish/Subscribe Systems with Distributed Hash Tables and Languages from Information Retrieval}, booktitle = {Proceedings of the 6th Workshop on Distributed Data and Structures (WDAS)}, year = {2004}, month = {July}, address = {Lausanne, Switzerland}, author = {Christos Tryfonopoulos and Manolis Koubarakis} } @conference {567, title = {Query Processing in Super-Peer Networks with Languages Based on Information Retrieval: the P2P-DIET Approach}, booktitle = {Proceedings of the International Workshop on Peer-to-peer Computing and Databases (P2P\&DB @ EDBT)}, year = {2004}, month = {March}, address = {Herakion, Greece}, author = {Stratos Idreos and Christos Tryfonopoulos and Manolis Koubarakis and Yannis Drougas} } @conference {Lepouras_tailorabilityin, title = {Tailorability in the context of E-government Information Systems: An approach}, booktitle = {Proceedings of the IRMA 2004 conference}, year = {2004}, month = {5}, abstract = {The ever changing environment information systems model, and in particular e-government ones, intensifies the need for systems that are able to easily, efficiently and transparently adapt to changing environments. Accommodating unanticipated changes implies that systems must be able to adapt to changes occurring in and evolve in step with their changing environment. Adaptation is concerned with monitoring, analysing and understanding the patterns of the user{\textquoteright}s interaction with the system. Similarly, an information system is said to be evolutionary if it can be purposefully used in a dynamic environment. E-government information systems, in virtue of their nature and function, are driven by the need to adapt and evolve. This suggests that the design and implementation of such systems must provide the necessary infrastructure for evolution and adaptability. In other words, e-government information systems must abide to the Tailorable Information Systems paradigm. In this work we present a case study for the development of a Tailorable e-government information system.}, author = {Giorgos Lepouras and Anya Sotiropoulou and Dimitrios Theotokis and Costas Vassilakis} } @conference {gorilas2003, title = {E-forms services for the Public Sector: Shifting Development Effort from Programmers to Domain Experts}, booktitle = {Proceedings of e-Challenges 2003}, year = {2003}, month = {10}, abstract = {E-forms have a central role in a significant number of e-government services. This paper presents a knowledge-based technical platform aiming to assist public sector employees to generate online transaction services by simplifying their development, maintenance and integration with installed IT systems. At the heart of this platform lies the knowledge and transaction services repository. This repository consists of a number of XML document types that incorporate all necessary details for creating and managing online transaction services. The main underlying idea is to provide a platform with intuitive interfaces that can be used directly by domain experts thus minimising the need for personnel with IT skills. This platform is currently under development within the IST SmartGov project.}, author = {Stelios Gorilas and Costas Vassilakis and Tomas Pariente Lobo and E. Tambouris} } @article {577, title = {Selective Information Dissemination in P2P Networks: Problems and Solutions}, journal = {SIGMOD Record, Special Issue on Peer-to-Peer Data Management}, volume = {32}, year = {2003}, pages = {71-76}, author = {Manolis Koubarakis and Christos Tryfonopoulos and Stratos Idreos and Yannis Drougas}, editor = {Karl Aberer} } @proceedings {DBLP:conf/chorochronos/2003, title = {Spatio-Temporal Databases: The CHOROCHRONOS Approach}, volume = {2520}, year = {2003}, publisher = {Springer}, isbn = {3-540-40552-6}, doi = {10.1007/b83622}, url = {https://doi.org/10.1007/b83622}, editor = {Manolis Koubarakis and Timos K. Sellis and Andrew U. Frank and St{\'e}phane Grumbach and Ralf Hartmut G{\"u}ting and Christian S. Jensen and Nikos A. Lorentzos and Yannis Manolopoulos and Enrico Nardelli and Barbara Pernici and Hans-J{\"o}rg Schek and Michel Scholl and Babis Theodoulidis and Nectaria Tryfona} } @conference {536, title = {Data Models and Languages for Agent-Based Textual Information Dissemination}, booktitle = {Proceedings of the 6th International Workshop on Cooperative Information Agents (CIA)}, year = {2002}, month = {September}, publisher = {Springer}, organization = {Springer}, address = {Madrid, Spain}, author = {Manolis Koubarakis and Christos Tryfonopoulos and Paraskevi Raftopoulou and Theodoros Koutris} } @proceedings {DBLP:conf/dolap/2002, title = {DOLAP 2002, ACM Fifth International Workshop on Data Warehousing and OLAP, November 8, 2002, McLean, VA, USA, Proceedings}, year = {2002}, publisher = {ACM}, isbn = {1-58113-590-4}, editor = {Il-Yeol Song and Dimitri Theodoratos} } @conference {572, title = {Efficient Agent-Based Dissemination of Textual Information}, booktitle = {Proceedings of the 2nd Hellenic Conference on Artificial Intelligence (SETN)}, year = {2002}, month = {April}, address = {Thessaloniki, Greece}, author = {Manolis Koubarakis and Theodoros Koutris and Paraskevi Raftopoulou and Christos Tryfonopoulos} } @conference {546, title = {Information Alert in Distributed Digital Libraries: The Models, Languages, and Architecture of DIAS}, booktitle = {Proceedings of the 6th European Conference on Research and Advanced Technology for Digital Libraries (ECDL)}, year = {2002}, month = {September}, address = {Rome, Italy}, author = {Manolis Koubarakis and Theodoros Koutris and Christos Tryfonopoulos and Paraskevi Raftopoulou} } @conference {584, title = {Peer-to-peer Agent Systems for Textual Information Dissemination: Algorithms and Complexity}, booktitle = {Proceedings of the UK Workshop on Multiagent Systems (UKMAS)}, year = {2002}, month = {December}, address = {Liverpool, UK}, author = {Manolis Koubarakis and Christos Tryfonopoulos} } @conference {lep2002a1, title = {SMARTGOV: A Governmental Knowledge-based Platform for Public Sector Online Services}, booktitle = {Proceedings KMGov2002}, year = {2002}, month = {5}, pages = {173{\textendash}185}, address = {Copenhagen, Denmark}, abstract = {Public transaction services (such as e-forms), although perceived the future of e-government have not yet realised their full potential. E-forms have a significant role in e-government, as they are the basis for realising most of the twenty public services that all European Union member states have to provide to their citizens and businesses. The aim of this paper is to present a knowledge-based platform to assist public sector employees to generate online transaction services by simplifying their development, maintenance and integration with already installed IT systems.}, author = {E. Tambouris and G. Boukis and Costas Vassilakis and Giorgos Lepouras and S. Rouvas and Canadas, R. and Heredia, S. and Lopez Usero, J. C.} } @conference {Georgiadis_2002, title = {SmartGov: A Knowledge-Based Platform for Transactional Electronic Services}, booktitle = {Lecture Notes in Computer Science}, year = {2002}, month = {9}, pages = {362-369}, publisher = {Springer Berlin Heidelberg}, organization = {Springer Berlin Heidelberg}, abstract = {Public transaction services (such as e-forms) although perceived the future of e-government have not yet realised their full potential. E-forms have a significant role in e-government, as they are the basis for implementing most of the twenty public services that all member states have to provide to their citizens and businesses. The aim of the SmartGov project is to specify, develop, deploy and evaluate a knowledge-based platform to assist public sector employees to generate online transaction services by simplifying their development, maintenance and integration with already installed IT systems. This platform will be evaluated in two European countries (in one Ministry and one Local Authority). This paper outlines key issues in the development of the SmartGov system platform.}, doi = {10.1007/978-3-540-46138-8_59}, url = {https://link.springer.com/chapter/10.1007/978-3-540-46138-8_59}, author = {P. Georgiadis and Giorgos Lepouras and Costas Vassilakis and G. Boukis and E. Tambouris and S. Gorilas and E. Davenport and A. Macintosh and J. Fraser and D. Lochhead} } @proceedings {DBLP:conf/ssd/2001, title = {Advances in Spatial and Temporal Databases, 7th International Symposium, SSTD 2001, Redondo Beach, CA, USA, July 12-15, 2001, Proceedings}, volume = {2121}, year = {2001}, publisher = {Springer}, isbn = {3-540-42301-X}, doi = {10.1007/3-540-47724-1}, url = {https://doi.org/10.1007/3-540-47724-1}, editor = {Christian S. Jensen and Markus Schneider and Bernhard Seeger and Vassilis J. Tsotras} } @conference {599, title = {Agents in Decentralised Information Ecosystems: The DIET Approach}, booktitle = {Symposium on Information Agents for E-Commerce, AISB Convention}, year = {2001}, month = {March}, address = {University of York, United Kingdom}, abstract = {The complexity of the current global information infrastructure requires novel means of understanding and exploiting the dynamics of information. One means may be through the concept of an information ecosystem. An information ecosystem is analogous to a natural ecosystem in which there are flows of materials and energy analogous to information flow between many interacting individuals. This paper describes a multi-agent platform, DIET (Decentralised Information Ecosystem Technologies) that can be used to implement open, robust, adaptive and scalable ecosystem-inspired systems. We describe the design principles of the DIET software architecture, and present a simple example application based upon it. We go on to consider how the DIET system can be used to develop information brokering agents, and how these can contribute to the implementation of economic interactions between agents, as well as identifying some open questions relating to research in these areas. In this way we show the capacity of the DIET system to support applications using information agents.}, author = {P. Marrow and Manolis Koubarakis and R.H. van Lengen and F. Valverde-Albacete and E. Bonsma and J. Cid-Suerio and A.R. Figueiras-Vidal and A. Gallardo-Antolin and C. Hoile and T. Koutris and H. Molina-Bulla and A. Navia-Vazquez and Paraskevi Raftopoulou and N. Skarmeas and Christos Tryfonopoulos and F. Wang and C. Xiruhaki} } @conference {aisb01-MKL+, title = {Agents in Decentralised Information Ecosystems: The DIET Approach}, booktitle = {Proccedings of the Symposium on Information Agents for E-Commerce, AISB Convention}, year = {2001}, month = {March}, pages = {109{\textendash}117}, address = {York, UK}, author = {P. Marrow and Manolis Koubarakis and R.H. van Lengen and F. Valverde-Albacete and E. Bonsma and J. Cid-Suerio and A.R. Figueiras-Vidal and A. Gallardo-Antolin and C. Hoile and T. Koutris and H. Molina-Bulla and A. Navia-Vazquez and Paraskevi Raftopoulou and N. Skarmeas and Christos Tryfonopoulos and F. Wang and C. Xiruhaki} } @conference {797082, title = {Distributed Information Systems Tailorability: A Component Approach}, booktitle = {FTDCS {\textquoteright}99: Proceedings of the 7th IEEE Workshop on Future Trends of Distributed Computing Systems}, year = {1999}, month = {12}, pages = {95}, publisher = {IEEE Computer Society}, organization = {IEEE Computer Society}, address = {Washington, DC, USA}, abstract = {Distributed software systems need to evolve according to the ever-changing requirements on which they were built. Software systems{\textquoteright} tailorability can be achieved in terms of component software. Atoms and molecules the basic constructs of the ATOMA framework are the building blocks for distributed tailorable component-based software systems. These constructs can be considered as independent agents, that communicate in terms of unanticipated, connections that are established at runtime, thus forming agent communities. System tailorability can take place at two levels. In high level tailorability whole parts of the functionality of a system, represented as agents, can be altered in order to provide new functionality. At a lower level, the tailorability of an agent itself that is the tailorability of its functionality, is achieved through a flexible service mapping implementation for rule-based method invocation.}, isbn = {0-7695-0468-X}, doi = {10.1109/FTDCS.1999.818790}, author = {Dimitrios Theotokis and Kapos, G. D. and Costas Vassilakis and Anya Sotiropoulou and Gyftodimos, G.} }