@article {835, title = {On the Quality and Validity of Course Evaluation Questionnaires Used in Tertiary Education in Greece}, journal = {Trends in Higher Education}, volume = {3}, year = {2024}, pages = {221{\textendash}234}, abstract = {

In compliance with national legislation, Greek tertiary education institutions assess educational quality often using a standardized anonymous questionnaire completed by students. This questionnaire aims to independently evaluate various course components, including content organization, instructor quality, facilities, infrastructure, and grading methods. Despite widespread use across universities, the questionnaire{\textquoteright}s validity remains unexamined. This study addresses this gap by analyzing 48,000+ questionnaire responses from the University of the Peloponnese (2014{\textendash}2022), encompassing 68 undergraduate and graduate programs. Confirmatory factor analyses were used to assess the quality of the questionnaire, while exploratory factor analyses were used to assess the dimensions of the tool based on the data. Both analyses reveal shortcomings: confirmatory analysis detects strong correlations between supposedly different factors, and exploratory analysis identifies dimensions inconsistent with the expected structure. These findings question the questionnaire{\textquoteright}s quality and the validity of drawn conclusions, while additionally identifying opportunities for reducing the number of questions, which can contribute to increased questionnaire submission rates. Given its common use across Greek universities and its influence on shaping courses, urgent redesigning of the questionnaire for tertiary education evaluation is recommended.

}, keywords = {CFA, EFA, Higher Education, quality assurance}, doi = {https://doi.org/10.3390/higheredu3020013}, url = {https://www.mdpi.com/2813-4346/3/2/13}, author = {Papadogiannis, Ilias and Vassilakis, Costas and Wallace, Manolis and Katsis, Athanassios} } @article {831, title = {Blockchain meets Internet of Things (IoT) forensics: A unified framework for IoT ecosystems}, journal = {Internet of Things}, year = {2023}, month = {oct}, pages = {100968}, abstract = {

With the continuously increasing number of security incidents targeting sensors, embedded devices, and other electronics appliances and systems that comprise the so-called Internet of things (IoT), the field of IoT forensics emerged as a branch of digital forensics focusing on the investigation of attacks in the IoT ecosystem. Digital evidence authenticity, integrity, confidentiality, and privacy are among the factors affecting the investigation process in IoT forensics, which can be addressed by employing the blockchain as the means not only for the preservation of digital evidence, but also for other steps of a digital forensics investigation process. The high-level goal of the paper is three-fold: to establish a holistic IoT forensics process as a reference point against which blockchain integration patterns and best practices will be identified in order to yield a robust, widely accepted and scalable architecture of the blockchain-enabled solution; to integrate the blockchain with the proposed IoT forensics process for addressing the above challenges; and to evaluate the overall solution highlighting improvements and potential performance bottlenecks. The proposed blockchain-enabled platform leverages multi-access edge computing and has been implemented with Hyperledger Fabric on an extensive virtualized testbed providing a realistic smart home environment. A thorough evaluation was conducted with real cyber-attacks generating digital evidence at high rates for testing the platform{\textquoteright}s behavior at high load. The experimental results showed that the proposed platform achieved high throughput, excessively low latency, and zero error rate in the operation of the blockchain network.

}, keywords = {blockchain, cyber-security, Digital forensics, Edge computing, Internet of Things}, doi = {10.1016/j.iot.2023.100968}, url = {https://www.sciencedirect.com/science/article/pii/S2542660523002913}, author = {Sotirios Brotsis and Konstantinos P. Grammatikakis and Dimitrios Kavallieros and Antonio I. Mazilu and Nicholas Kolokotronis and Konstantinos Limniotis and Costas Vassilakis} } @article {828, title = {Chatbots for Cultural Venues: A Topic-Based Approach}, journal = {Algorithms}, volume = {16}, year = {2023}, month = {jul}, pages = {339}, abstract = {

Digital assistants{\textemdash}such as chatbots{\textemdash}facilitate the interaction between persons and machines and are increasingly used in web pages of enterprises and organizations. This paper presents a methodology for the creation of chatbots that offer access to museum information. The paper introduces an information model that is offered through the chatbot, which subsequently maps the museum{\textquoteright}s modeled information to structures of DialogFlow, Google{\textquoteright}s chatbot engine. Means for automating the chatbot generation process are also presented. The evaluation of the methodology is illustrated through the application of a real case, wherein we developed a chatbot for the Archaeological Museum of Tripolis, Greece.

}, keywords = {chatbots, cultural venues, Museums, RDF triples, topics}, doi = {10.3390/a16070339}, url = {https://doi.org/10.3390/a16070339}, author = {Vasilis Bouras and Dimitris Spiliotopoulos and Dionisis Margaris and Costas Vassilakis and Konstantinos Kotis and Angeliki Antoniou and George Lepouras and Manolis Wallace and Vassilis Poulopoulos} } @article {818, title = {Disruptive Technologies for Parliaments: A Literature Review}, journal = {Future Internet}, volume = {15}, year = {2023}, month = {feb}, pages = {66}, abstract = {

Exploitation and use of disruptive technologies, such as the Internet of Things, recommender systems, and artificial intelligence, with an ambidextrous balance, are a challenge, nowadays. Users of the technologies, and stakeholders, could be part of a new organisational model that affects business procedures and processes. Additionally, the use of inclusive participatory organisational models is essential for the effective adoption of these technologies. Such models aim to transform organisational structures, as well. Public organisations, such as the parliament, could utilise information systems{\textquoteright} personalisation techniques. As there are a lot of efforts to define the framework, the methodology, the techniques, the platforms, and the suitable models for digital technologies adoption in public organisations, this paper aims to provide a literature review for disruptive technology inclusive use in parliaments. The review emphasises the assessment of the applicability of the technologies, their maturity and usefulness, user acceptance, their performance, and their correlation to the adoption of relevant innovative, inclusive organisational models. It is argued that the efficient digital transformation of democratic institutions, such as parliaments, with the use of advanced e-governance tools and disruptive technologies, requires strategic approaches for adoption, acceptance, and inclusive service adaptation.

}, keywords = {artificial intelligence, digital transformation, inclusiveness, Internet of Things, parliament, Recommender Systems}, doi = {https://doi.org/10.3390/fi15020066}, url = {https://www.mdpi.com/1999-5903/15/2/66}, author = {Dimitris Koryzis and Dionisis Margaris and Costas Vassilakis and Konstantinos Kotis and Dimitris Spiliotopoulos} } @conference {822, title = {Minimizing Software-Rooted Risk through Library Implementation Selection}, booktitle = {Proceedings of the 2023 IEEE CSR Workshop on Data Science for Cyber Security (DS4CS)}, year = {2023}, abstract = {

In contemporary Internet of Things (IoT) systems, complex software artifacts are deployed to realize the required functionalities. The business logic of these software artifacts is uniquely composed through code that is customly developed according to the requirements, while all software artifacts utilize libraries that implement generic functionalities, which are needed in the context of the realized operations. Libraries, however, often entail vulnerabilities, which may be exploited by threat agents to attack the system. In many cases, the functionality required by an application is realized by a number of alternative libraries, with each library having its own list of vulnerabilities, while differentiations in other non-functional properties (e.g. execution efficiency, memory footprint etc.) may also be present. In this paper, we present an approach for automating the task of minimizing the risk level of IoT systems that is owing to the vulnerabilities of libraries required by software artifacts. The proposed approach exploits knowledge on which libraries provide equivalent implementations of the same functionalities, and automatically assesses the risk level of candidate library combinations and finally selects the library configuration exhibiting the minimum risk level to bundle into the executable software artifact. Additionally, the risk level of candidate implementations is constantly monitored for new vulnerability identifications or fixes in the implementations, triggering new risk assessments and producing new executables as appropriate. The proposed approach can be used in IoT platform deployment to minimize the software-rooted risk level.

}, author = {Panagiotis Sotiropoulos and Christos-Minas Mathas and Costas Vassilakis and Nicholas Kolokotronis} } @article {823, title = {A Software Vulnerability Management Framework for the Minimization of System Attack Surface and Risk}, journal = {Electronics}, volume = {12}, year = {2023}, month = {may}, pages = {2278}, abstract = {

Current Internet of Things (IoT) systems comprise multiple software systems that are deployed to provide users with the required functionalities. System architects create system blueprints and draw specifications for the software artefacts that are needed; subsequently, either custom-made software is developed according to these specifications and/or ready-made COTS/open source software may be identified and customized to realize the overall system goals. All deployed software however may entail vulnerabilities, either due to insecure coding practices or owing to misconfigurations and unexpected interactions. Moreover, software artefacts may implement a much broader set of functionalities than may be strictly necessary for the system at hand, in order to serve a wider range of needs, and failure to appropriately configure the deployed software to include only the required modules results in the further increase of the system attack surface and the associated risk. In this paper, we present a software vulnerability management framework which facilitates (a) the configuration of software to include only the necessary features, (b) the execution of security-related tests and the compilation of platform-wide software vulnerability lists, and (c) the prioritization of vulnerability addressing, considering the impact of each vulnerability, the associated technical debt for its remediation, and the available security budget. The proposed framework can be used as an aid in IoT platform implementation by software architects, developers, and security experts.

}, keywords = {IoT systems, risk management, software vulnerabilities, system design, system security, technical debt}, doi = {10.3390/electronics12102278}, url = {https://doi.org/10.3390/electronics12102278}, author = {Panagiotis Sotiropoulos and Christos-Minas Mathas and Costas Vassilakis and Nicholas Kolokotronis} } @conference {812, title = {Persona Finetuning for Online Gaming using Personalisation Techniques}, booktitle = {Proceedings of the 2022 HCII Conference}, year = {2022}, abstract = {

Automatic persona generation has been shown to have specific measurable benefits for application creators and users. In most situations, personas are adequately descriptive and diversified to achieve user type accuracy and coverage. For specific market segments, such as online gaming, using personas may accurately describe existing user base but not changing habit and need that are introduced by the fluidity of the offerings and the delivery methods. Changes in the ways that applications are marketed, such as new payment methods, for example, subscription models, pay-to-play and pay-to-win, payment-driven-gamification, seriously affect user needs and result in direct impact on user acceptance. This work utilises structured user needs from online gaming players to augment personas using personalisation techniques. The personas are finetuned and dediversified to result in concise personas, based on user needs that successfully convey information for creators and users alike.

}, keywords = {collaborative filtering, Data-driven methods, Diversification, Online Gaming, Persona, Personalisation, Usability evaluation, User study}, author = {Dimitris Spiliotopoulos and Dionisis Margaris and Kostas N. Koutrakis and Panos Philippopoulos and Costas Vassilakis} } @article {797, title = {On Addressing the Low Rating Prediction Coverage in Sparse Datasets Using Virtual Ratings}, journal = {SN Computer Science}, volume = {2}, year = {2021}, month = {May}, pages = {255}, abstract = {

Collaborative filtering-based recommendation systems consider users{\textquoteright} likings and interests, articulated as ratings within a database to offer personalized recommendations. Unfortunately, many collaborative filtering datasets exhibit the {\textquoteleft}{\textquoteleft}grey sheep{\textquoteright}{\textquoteright} phenomenon, a state where no near neighbours can be found for certain users. This phenomenon is extremely frequent in datasets where users, on average, have rated only a small percentage of the available items, which are termed as sparse datasets. This paper addresses the {\textquoteleft}{\textquoteleft}grey sheep{\textquoteright}{\textquoteright} problem by proposing the virtual ratings concept and introduces an algorithm for virtual rating creation on the basis of actual ratings. The novelty behind this concept is that the introduction of the virtual ratings effectively reduces the user{\textendash}item rating matrix sparsity, thus alleviating the aforementioned problem. The proposed algorithm, which is termed as CFVR, has been extensively evaluated and the results show that it achieves to considerably improve the capability of a collaborative filtering system to formulate tailored recommendations for each user, when operating on sparse datasets, while at the same time improves rating prediction quality.

}, keywords = {collaborative filtering, Cosine Similarity, Evaluation, Pearson Correlation Coefficient, Recommender Systems, Sparse Datasets, Virtual ratings}, issn = {2661-8907}, doi = {10.1007/s42979-021-00668-8}, url = {https://doi.org/10.1007/s42979-021-00668-8}, author = {Margaris, Dionisis and Spiliotopoulos, Dimitris and Karagiorgos, Gregory and Vassilakis, Costas and Vasilopoulos, Dionysios} } @conference {799, title = {Cyber-Security Training Evaluation Metrics}, booktitle = {Proceedings of the 2021 IEEE International Conference on Cyber Security and Resilience}, year = {2021}, publisher = {IEEE}, organization = {IEEE}, abstract = {

Cyber-security training has evolved into an imperative need, aiming to provide cyber-security professionals with the knowledge and skills required to confront cyber-attacks that are increasing in number and sophistication. Training activities are typically associated with evaluation means, aimed to assess the extent to which the trainee has acquired the knowledge and skills whose development is targeted by the training programme, while cyber-security awareness and skill level evaluation means may be used to support additional security-related aspects of organizations. In this paper, we review trainee performance assessment metrics in cyber-security training, aiming to assist designers of cyber-security training activities to identify the mostprominent trainee performance assessment means for their training programmes, while additional research directions involving cyber-security training evaluation metrics are also identified.

}, keywords = {Cyber-ranges, Cyber-security training, Evaluation, Gamification, Scoring}, author = {Koutsouris, Nikolaos and Vassilakis, Costas and Kolokotronis, Nicholas} } @article {798, title = {On the Design of IoT Security: Analysis of Software Vulnerabilities for Smart Grids}, journal = {Energies}, volume = {14}, year = {2021}, month = {may}, pages = {2818}, abstract = {

The 5G communication network will underpin a vast number of new and emerging services, paving the way for unprecedented performance and capabilities in mobile networks. In this setting, the Internet of Things (IoT) will proliferate, and IoT devices will be included in many 5G application contexts, including the Smart Grid. Even though 5G technology has been designed by taking security into account, design provisions may be undermined by software-rooted vulnerabilities in IoT devices that allow threat actors to compromise the devices, demote confidentiality, integrity and availability, and even pose risks for the operation of the power grid critical infrastructures. In this paper, we assess the current state of the vulnerabilities in IoT software utilized in smart grid applications from a source code point of view. To that end, we identified and analyzed open-source software that is used in the power grid and the IoT domain that varies in characteristics and functionality, ranging from operating systems to communication protocols, allowing us to obtain a more complete view of the vulnerability landscape. The results of this study can be used in the domain of software development, to enhance the security of produced software, as well as in the domain of automated software testing, targeting improvements to vulnerability detection mechanisms, especially with a focus on the reduction of false positives.

}, keywords = {Internet of Things, robustness, security, software vulnerabilities}, doi = {10.3390/en14102818}, author = {Christos-Minas Mathas and Costas Vassilakis and Nicholas Kolokotronis and Charilaos C. Zarakovitis and Michail-Alexandros Kourtis} } @inbook {796, title = {Handbook of Research on Developing a Post-Pandemic Paradigm for Virtual Technologies in Higher Education}, year = {2021}, publisher = {IGI Global}, organization = {IGI Global}, chapter = {Social Skills and Online Learning}, abstract = {

The concept of online teaching and learning is widely adopted by universities due to the pandemic of COVID-19, which forced them to shift from blending learning (including both direct and remote education) to exclusive online education. Technology has provided a multitude of tools which can prove very useful in the hands of people who want to serve such a great purpose as education. During the days of the pandemic, where people are isolated, virtual community and virtual learning technology brings people together to experience a sense of educational community in the virtual world. This chapter introduces the reader to the importance for social skill training of the learning communities during times that online learning is the sole type of education, exploring methodologies, tools and practices that can be used to counterbalance the deficiencies introduced by distance learning methods regarding social skill development.

}, keywords = {Active learning, Community of Inquiry, COVID-19, Digital Collaboration Platforms, Higher Education, Pandemic, Problem-Based Learning, Remote Learning, Social skills, Virtual Learning Community}, author = {Kriemadis, Athanasios and Kapnisi, Dimitra and Vassilakis, Costas and Spiliotopoulos Dimitris} } @conference {800, title = {Understanding and mitigating banking trojans: From Zeus to Emotet}, booktitle = {Proceedings of the 2021 IEEE International Conference on Cyber Security and Resilience}, year = {2021}, publisher = {IEEE}, organization = {IEEE}, abstract = {

Banking Trojans came a long way in the past decade, and the recent case of Emotet showed their enduring relevance. The evolution of the modern computing landscape can be traced through Emotet and Zeus, both representative examples from the end of the past decade. As an example of earlier malware, Zeus only needed to employ simple anti-analysis techniques to stay undetected; while the more recent Emotet had to constantly evolve to stay a step ahead. Current host-based antimalware solutions face an increasing number of obstacles to perform their function. A multi-layer approach to network security is necessary for network-based intrusion response systems to secure modern networks of heterogeneous devices. A system based on a combination of a graphical network security model and a game theoretic model of cyber attacks was tested on a testbed with Windows machines infected with Trojans; experimental results showed that the proposed system effectively blocked Trojans{\textquoteright} network communications effectively preventing data leakage and yielding encouraging results for future work.

}, keywords = {Cyber security, Graphical security models, Intrusion response systems, Malware analysis, Reverse engineering}, author = {Grammatikakis, Konstantinos-Panagiotis and Koufos, Ioannis and Kolokotronis, Nicholas and Vassilakis, Costas and Shiaeles, Stavros} } @article {771, title = {An Adaptive Social Network-Aware Collaborative Filtering Algorithm for Improved Rating Prediction Accuracy}, journal = {IEEE Access}, volume = {8}, year = {2020}, pages = {68301{\textendash}68310}, abstract = {When information from traditional recommender systems is augmented with information about user relationships that social networks store, more successful recommendations can be produced. However, this information regarding user relationships may not always be available, since some users may not consent to the use of their social network information for recommendations or may not have social network accounts at all. Moreover, the rating data (categories and characteristics of products) may be unavailable for a recommender system. In this paper, we present an algorithm that can be applied in any social network-aware recommender system that utilizes the users{\textquoteright} ratings on items and users{\textquoteright} social relations. The proposed algorithm addresses the issues of limited social network information or limited collaborative filtering information for some users by adapting its behavior, taking into account the density and utility of each user{\textquoteright}s social network and collaborative filtering neighborhoods. Through this adaptation, the proposed algorithm achieves considerable improvement in rating prediction accuracy. Furthermore, the proposed algorithm can be easily implemented in recommender systems}, keywords = {Performance evaluation, Recommender Systems, Social computing}, issn = {2169-3536}, doi = {10.1109/access.2020.2981567}, author = {Dionisis Margaris and Anna Kobusinska and Dimitris Spiliotopoulos and Costas Vassilakis} } @article {779, title = {An Algorithm for Density Enrichment of Sparse Collaborative Filtering Datasets Using Robust Predictions as Derived Ratings}, journal = {Algorithms}, volume = {13}, year = {2020}, month = {07/2020}, pages = {174}, abstract = {

Collaborative filtering algorithms formulate personalized recommendations for a user, first by analysing already entered ratings to identify other users with similar tastes to the user (termed as near neighbours), and then using the opinions of the near neighbours to predict which items the target user would like. However, in sparse datasets, too few near neighbours can be identified, resulting in low accuracy predictions and even a total inability to formulate personalized predictions. This paper addresses the sparsity problem by presenting an algorithm that uses robust predictions, that is predictions deemed as highly probable to be accurate, as derived ratings. Thus, the density of sparse datasets increases, and improved rating prediction coverage and accuracy are achieved. The proposed algorithm, termed as CFDR, is extensively evaluated using (1) seven widely-used collaborative filtering datasets, (2) the two most widely-used correlation metrics in collaborative filtering research, namely the Pearson correlation coefficient and the cosine similarity, and (3) the two most widely-used error metrics in collaborative filtering, namely the mean absolute error and the root mean square error. The evaluation results show that, by successfully increasing the density of the datasets, the capacity of collaborative filtering systems to formulate personalized and accurate recommendations is considerably improved.

}, keywords = {collaborative filtering, density enrichment, derived ratings, rating prediction accuracy, rating prediction coverage, Recommender Systems, robust predictions, Sparse Datasets}, doi = {https://doi.org/10.3390/a13070174}, author = {Dionisis Margaris and Dimitris Spiliotopoulos and Gregory Karagiorgos and Costas Vassilakis} } @conference {795, title = {From Smart Cities to Smart Rural Country: challenges and sustainability}, booktitle = {Extended abstract Presentation in the 15th National and International Conderence of the Hellenic Society for Systemic Studies}, year = {2020}, abstract = {

This work presents the current progress on smart cities initiatives, major breakthroughs and challenges. It also reviews the smart villages and smart rural environments as the next evolution of the smart cities vision. The purpose of the Smart Cities Mission is to drive economic growth and improve the quality of life of people by enabling local area development and harnessing technology, especially technology that leads to Smart outcomes. Technologies such as IoT (sensors, networks and applications) can be leveraged to improve city services, utilities, the environment and quality of life. All technologies have a common base, big data. Relevant data are collected by local sensors, such as citizens and local activities and global sensors, such as the environment, financial institutions and government sources. Data from disparate sources (traffic, air/water quality and usage, energy usage, resident movement) is constantly collected and is available for analysis The aim is to use the already gained expertise and insights from the smart cities approaches, applications and evaluations as well as the early works on smart villages and rural spaces to formulate the challenges and sustainability goals for the smart rural country. The findings of this work are mostly applied to medium- and long-term challenges as well as toward the notion of smart communities. Smart communities represent the notion of abstract connected objects within or spanning smart urban and rural spaces, such as smart cultural heritage, smart environment, and others. Introducing the non-technical goals for smart communities provides the sense of purpose and tangible targets for the technical-oriented smart urban and rural approaches, for aspiration and sustainability planning for the future.

}, author = {Dimitris Spiliotopoulos and Athanasios Kriemadis 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} } @inbook {780, title = {Reconnaisance}, booktitle = {Cyber-Security Threats, Actors, and Dynamic Mitigation}, year = {2020}, publisher = {CRC Press}, organization = {CRC Press}, abstract = {

Reconnaissance is the phase of gathering information about an organization{\textquoteright}s network and computing devices. This information includes both technical characteristics, such as IP addresses and software, and non-technical aspects, such as people operating the devices and the business value of tangible or intangible assets associated with the computing infrastructure. This information allows attackers to better understand their target and prepare elaborate attack plans. The reconnaissance phase is itself divided in a number of subphases, and each subphase is supported by a multitude of tools. In this chapter, we firstly describe in more detail the reconnaissance phase, while subsequently we present the different subphases and the methods and tools supporting each one, providing specific examples of how reconnaissance actions are performed. The information presented in this chapter can be used by organizations{\textquoteright} cyber-security officers to identify weaknesses in the organizations{\textquoteright} security plan implementations and take appropriate mitigation measures.

}, keywords = {Actors, Cyber-Security Threats, Dynamic Mitigation, Reconnaissance}, author = {Mathas, Christos-Minas and Vassilakis, Costas}, editor = {Nicholas Kolokotronis and Stavros Shiaeles} } @article {770, title = {A Semantic Mixed Reality Framework for Shared Cultural Experiences Ecosystems}, journal = {Big Data and Cognitive Computing}, volume = {4}, year = {2020}, month = {4/2020}, pages = {6}, abstract = {This paper presents SemMR, a semantic framework for modelling interactions between human and non-human entities and managing reusable and optimized cultural experiences, towards a shared cultural experience ecosystem that might seamlessly accommodate mixed reality experiences. The SemMR framework synthesizes and integrates interaction data into semantically rich reusable structures and facilitates the interaction between different types of entities in a symbiotic way, within a large, virtual, and fully experiential open world, promoting experience sharing at the user level, as well as data/application interoperability and low-effort implementation at the software engineering level. The proposed semantic framework introduces methods for low-effort implementation and the deployment of open and reusable cultural content, applications, and tools, around the concept of cultural experience as a semantic trajectory or simply, experience as a trajectory (eX-trajectory). The methods facilitate the collection and analysis of data regarding the behaviour of users and their interaction with other users and the environment, towards optimizing eX-trajectories via reconfiguration. The SemMR framework supports the synthesis, enhancement, and recommendation of highly complex reconfigurable eX-trajectories, while using semantically integrated disparate and heterogeneous related data. Overall, this work aims to semantically manage interactions and experiences through the eX-trajectory concept, towards delivering enriched cultural experiences.}, keywords = {cultural experience, intelligent interaction, Mixed Reality, semantics, Usability}, doi = {https://doi.org/10.3390/bdcc4020006}, author = {Costas Vassilakis and Konstantinos Kotis and Dimitris Spiliotopoulos and Dionisis Margaris and Vlasios Kasapakis and Christos-Nikolaos Anagnostopoulos and Georgios Santipantakis and George A. Vouros and Theodore Kotsilieris and Volha Petukhova and Andrei Malchanau and Ioanna Lykourentzou and Kaj Michael Helin and Artem Revenko and Nenad Gligoric and Boris Pokric} } @conference {777, title = {Semantics-Driven Conversational Interfaces for Museum Chatbots}, booktitle = {Proceedings of the 22nd International Conference on Human-Computer Interaction, volume "Culture and Computing"}, year = {2020}, publisher = {Springer International Publishing}, organization = {Springer International Publishing}, abstract = {

This work addresses the challenges of creating usable and personalized conversational interfaces for broad, yet applicable, domains that require user engagement and learning, such as museum chatbots. Whether the chatbots are standalone or coupled with virtual agents or real-life robots, the functional requirements for interaction that targets specific learning aspects would be expected to be more or less similar. This work reports on experimental semantics-driven conversational interface design for chatbots in museum settings, targeting visitors to converse about exhibits and learn information about their style, the artists, the era, and other aspects related to them. Depending on the semantics (presentation, learning, exploration), chatbot scenarios were designed and evaluated by participants in a formative evaluation. The evaluation show that user requirement perception manifests in expectations on the semantic level, instead of just the technical level. The results between the scenarios are compared to see how the semantics considered for the design transferred to the implementation and to the user perception.

}, keywords = {chatbots, conversational interfaces, cultural technology, semantics}, doi = {10.1007/978-3-030-50267-6_20}, author = {Dimitris Spiliotopoulos and Konstantinos Kotis and Costas Vassilakis and Dionisis Margaris} } @conference {778, title = {{\textquotedblleft}Talking{\textquotedblright} Triples to Museum Chatbots}, booktitle = {Proceedings of the 22nd International Conference on Human-Computer Interaction, volume "Culture and Computing"}, year = {2020}, publisher = {Springer International Publishing}, organization = {Springer International Publishing}, abstract = {

The paper presents recent work on the design and development of AI chatbots for museums using Knowledge Graphs (KGs). The utilization of KGs as a key technology for implementing chatbots raises not only issues related to the representation and structuring of exhibits{\textquoteright} knowledge in suitable formalism and models, but also issues related to the translation of natural language dialogues to and from the selected technology for the formal representation and structuring of information and knowledge. Moreover, such a translation must be as transparent as possible to visitors, towards a realistic human-like question-answering process. The paper reviews and evaluates a number of recent approaches for the use of KGs in developing AI chatbots, as well as key tools that provide solutions for natural language translation and the querying of Knowledge Bases and Linked Open Data sources. This evaluation aims to provide answers to issues that are identified within the proposed MuBot approach for designing and implementing AI chatbots for museums. The paper also presents Cretan MuBot, the first experimental KG/Ontology-based AI chatbot of the MuBot Platform, which is under development in the Heracleum Archaeological Museum.

}, keywords = {chatbots, knowledge graphs, Museums, NLP, RDF triples}, doi = {10.1007/978-3-030-50267-6_22}, author = {Savvas Varitimiadis and Konstantinos Kotis and Dimitris Spiliotopoulos and Costas Vassilakis and Dionisis Margaris} } @conference {783, title = {Threat landscape for smart grid systems}, booktitle = {Proceedings of the 15th International Conference on Availability, Reliability and Security}, year = {2020}, month = {jul}, publisher = {ACM}, organization = {ACM}, abstract = {

Smart Grids are energy delivery networks, constituting an evolution of power grids, in which a bidirectional flow between power providers and consumers is established. These flows support the transfer of electricity and information, in order to support automation actions in the context of the energy delivery network. Insofar, many smart grid implementations and implementation proposals have emerged, with varying degrees of feature delivery and sophistication. While smart grids offer many advantages, their distributed nature and information flow streams between energy producers and consumers enable the launching of a number of attacks against the smart grid infrastructure, where the related consequences may range from economic loss to complete failure of the smart grid. In this paper, we survey the threat landscape of smart grids, identifying threats that are specific to this infrastructure, providing an assessment of the severity of the consequences of each attack type, discerning features that can be utilized to detect attacks and listing methods that can be used to mitigate them.

}, keywords = {attack detection features, attack mitigation, attacks, security, Smart grids}, doi = {https://doi.org/10.1145/3407023.3409229}, author = {Christos-Minas Mathas and Konstantinos-Panagiotis Grammatikakis and Costas Vassilakis and Nicholas Kolokotronis and Vasiliki-Georgia Bilali and Dimitris Kavallieros} } @conference {789, title = {A Trust Management System for the IoT domain}, booktitle = {Proceedings the 2020 IEEE World Congress on Services (SERVICES)}, year = {2020}, publisher = {IEEE}, organization = {IEEE}, abstract = {

In modern internet-scale computing, interaction between a large number of parties that are not known a-priori is predominant, with each party functioning both as a provider and consumer of services and information. In such an environment, traditional access control mechanisms face considerable limitations, since granting appropriate authorizations to each distinct party is infeasible both due to the high number of grantees and the dynamic nature of interactions. Trust management has emerged as a solution to this issue, offering aids towards the automated verification of actions against security policies. In this paper, we present a trust- and risk-based approach to security, which considers status, behavior and associated risk aspects in the trust computation process, while additionally it captures user-to-user trust relationships which are propagated to the device level, through user-to-device ownership links.

}, keywords = {associated risk, behavior, Internet-of-things, status, trust management}, doi = {10.1109/SERVICES48979.2020.00047}, author = {Christos-Minas Mathas and Costas Vassilakis and Nicholas Kolokotronis} } @conference {785, title = {A User Interface for Personalized Web Service Selection in Business Processes}, booktitle = {Lecture Notes in Computer Science}, year = {2020}, publisher = {Springer International Publishing}, organization = {Springer International Publishing}, abstract = {

Nowadays, due to the huge volume of information available on the web, the need for personalization is more than necessary. Choosing the right information for each user is as important as the way this information is presented to him or her. Currently, user-triggered recommendation requests for web services are implemented as an automatic recommendation based on parametric computation. This work reports on a specialized user interface for business processes, where writing code entails invocation of business process information. The paper presents the user interface design for Personalized Web Service Selection in Business Process scenario execution and the user evaluation by business process engineers.

}, keywords = {adaptation, business processes, personalization, user interface, Web services, WS-BPEL}, doi = {10.1007/978-3-030-60152-2_41}, author = {Dionisis Margaris and Dimitris Spiliotopoulos and Costas Vassilakis and Gregory Karagiorgos} } @article {787, title = {Visualizing the educational data mining literature}, journal = {European Journal of Engineering Research and Science}, volume = {TBD}, year = {2020}, month = {TBD}, abstract = {

This article provides a visualization of a literature review in students{\textquoteright} performance prediction using educational data mining (EDM) techniques for the period 2015-2019. The results of the review are presented concisely and simply with the use of diagrams. Various aspects of the literature are examined, such as the algorithms adopted, the type of results drawn, the educational setting of the application and the actual exploitation of the outcomes. Findings indicate that tertiary education dominates the EDM field; in contrast, the focus given to secondary and primary education is minimal.

}, keywords = {Educational Data Mining, Literature review, Student Performance, Visualization}, author = {I. Papadogiannis and N. Platis and V. Poulopoulos and C. Vassilakis and G. Lepouras and M. Wallace and G. Karountzou} } @conference {Kolokotronis2019IEEESrv, title = {On Blockchain Architectures for Trust-based Collaborative Intrusion Detection}, booktitle = {Proceedings of the 1st IEEE Services Workshop on Cyber Security and Resilience in the Internet Of Things, within IEEE Services 2019}, year = {2019}, publisher = {IEEE}, organization = {IEEE}, abstract = {This paper considers the use of novel technologies for mitigating attacks that aim at compromising intrusion detection systems (IDSs). Solutions based on collaborative intrusion detection networks (CIDNs) could increase the resilience against such attacks as they allow IDS nodes to gain knowledge from each other by sharing information. However, despite the vast research in this area, trust management issues still pose significant challenges and recent works investigate whether these could be addressed by relying on blockchain and related distributed ledger technologies. Towards that direction, the paper proposes the use of a trust-based blockchain in CIDNs, referred to as trust-chain, to protect the integrity of the information shared among the CIDN peers, enhance their accountability, and secure their collaboration by thwarting insider attacks. A consensus protocol is proposed for CIDNs, which is a combination of a proof-of-stake and proof-of-work protocols, to enable collaborative IDS nodes to maintain a reliable and tampered-resistant trust-chain.}, keywords = {blockchain, collaborative intrusion detection, insider threats, security, trust management}, author = {Nicholas Kolokotronis and Sotirios Brotsis and Georgios Germanos and Costas Vassilakis and Stavros Shiaeles} } @conference {spiliot_iisa2019, title = {A Methodology for Generated Text Annotation for High Quality Speech Synthesis}, booktitle = {Proceedings of the 10th International Conference on Information, Intelligence, Systems and Applications (IISA2019)}, year = {2019}, month = {jul}, abstract = {Natural Language Generators may produce linguistically en-riched text descriptions that can lead to significantly improved quality of speech synthesis. There are cases, however, where either the generator modules produce pieces of non-analysed, non-annotated plain text, or such modules are not available at all. Moreover, the language analysis is restricted by the usually limited domain coverage of the generator. For those cases the enriched input to the speech synthesizer needs to be produced from plain text in order to maintain speech quality. This work reports on the method for automatic domain dependent annota-tion of plain text, through the utilisation of the linguistic infor-mation from rich generated text. The synthetic speech from the resulting prosody models is evaluated by human participants showing annotation results for plain text quite on par with the rich generated text. This leads to improved perceived natural-ness of the synthesized speech.}, keywords = {Natural language generation, Natural language processing, Prosody enrichment, Semantic feature annotation, Text-to-speech}, author = {Dimitris Spiliotopoulos and Costas Vassilakis and Dionisis Margaris and Konstantinos Kotis} } @conference {718, title = {A Mixed-reality Interaction-driven Game-based Learning Framework}, booktitle = {Proceedings of the 11th International Conference on Management of Digital EcoSystems (MEDES{\textquoteright}19)}, year = {2019}, publisher = {ACM}, organization = {ACM}, abstract = {This work presents a platform for linked legislative data to engage citizens in transparent and effective democracies. With a focus on scaling up participatory approaches from local to national level, the approach extends well established and open source tools and technologies, to build mobile monitoring and analysis tools that increase transparency of law-making and implementation to citizens. This is achieved by combining open data and open services with user and citizen generated content, in order to address citizen{\textquoteright}s needs in the context of open government. Data and feeds from trusted sources are interconnected with new and re-purposed data feeds generated by users via the social web to form a meaningful, searchable, customizable, re-usable and open data-focused personalised mobile public service approach. The framework exploits the social aspects of open data, as well as the training of users, citizens and public servants to be able to understand and demand useful public open data, as well as facilitate the opening of more data.}, keywords = {Accountability, Citizen Engagement, e-government, Legislation, Mobile Public Services, Natural language processing, Policy Modelling, Transparency}, author = {Dimitris Spiliotopoulos and Dionisis Margaris and Costas Vassilakis and Volha Petukhova and Konstantinos Kotis} } @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} } @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 {mathas2018a, title = {Evaluation of Apache Spot\textquotesingles machine learning capabilities in an SDN/NFV enabled environment}, booktitle = {Proceedings of the 13th International Conference on Availability, Reliability and Security - ARES 2018}, year = {2018}, publisher = {ACM Press}, organization = {ACM Press}, abstract = {Software Defined Networking (SDN) and Network Function Virtualisation (NFV) are transforming modern networks towards a service-oriented architecture. At the same time, the cybersecurity industry is rapidly adopting Machine Learning (ML) algorithms to improve detection and mitigation of complex attacks. Traditional intrusion detection systems perform signature-based detection, based on well-known malicious traffic patterns that signify potential attacks. The main drawback of this method is that attack patterns need to be known in advance and signatures must be preconfigured. Hence, typical systems fail to detect a zero-day attack or an attack with unknown signature. This work considers the use of machine learning for advanced anomaly detection, and specifically deploys the Apache Spot ML framework on an SDN/NFV-enabled testbed running cybersecurity services as Virtual Network Functions (VNFs). VNFs are used to capture traffic for ingestion by the ML algorithm and apply mitigation measures in case of a detected anomaly. Apache Spot utilises Latent Dirichlet Allocation to identify anomalous traffic patterns in Netflow, DNS and proxy data. We evaluate the overall performance of Apache Spot by deploying Denial of Service (Slowloris, BoNeSi) and a Data Exfiltration attack (iodine).}, keywords = {Apache Spot, Latent Dirichlet Allocation, Machine Learning, Network Function Virtualisation, Penetration Testing, SHIELD Project�, Software Defined Networking}, doi = {10.1145/3230833.3233278}, author = {Christos M. Mathas and Olga E. Segou and Georgios Xylouris and Dimitris Christinakis and Michail-Alexandros Kourtis and Costas Vassilakis and Anastasios Kourtis} } @conference {DBLP:conf/ssdbm/KaffesBSS18, title = {Finding shortest keyword covering routes in road networks}, booktitle = {Proceedings of the 30th International Conference on Scientific and Statistical Database Management, SSDBM 2018, Bozen-Bolzano, Italy, July 09-11, 2018}, year = {2018}, pages = {12:1{\textendash}12:12}, doi = {10.1145/3221269.3223038}, url = {https://doi.org/10.1145/3221269.3223038}, author = {Vassilis Kaffes and Alexandros Belesiotis and Dimitrios Skoutas and Spiros Skiadopoulos} } @article {DBLP:journals/jbd/Chatzigeorgakidis18, title = {FML-kNN: scalable machine learning on Big Data using \emphk-nearest neighbor joins}, journal = {J. Big Data}, volume = {5}, year = {2018}, pages = {4}, doi = {10.1186/s40537-018-0115-x}, url = {https://doi.org/10.1186/s40537-018-0115-x}, author = {Georgios Chatzigeorgakidis and Sophia Karagiorgou and Spiros Athanasiou and Spiros Skiadopoulos} } @article {DBLP:journals/dke/AllamSK18, title = {Improved suffix blocking for record linkage and entity resolution}, journal = {Data Knowl. Eng.}, volume = {117}, year = {2018}, pages = {98{\textendash}113}, doi = {10.1016/j.datak.2018.07.005}, url = {https://doi.org/10.1016/j.datak.2018.07.005}, author = {Amin Allam and Spiros Skiadopoulos and Panos Kalnis} } @article {DBLP:journals/tpds/JamourSK18, title = {Parallel Algorithm for Incremental Betweenness Centrality on Large Graphs}, journal = {IEEE Trans. Parallel Distrib. Syst.}, volume = {29}, number = {3}, year = {2018}, pages = {659{\textendash}672}, doi = {10.1109/TPDS.2017.2763951}, url = {https://doi.org/10.1109/TPDS.2017.2763951}, author = {Fuad Jamour and Spiros Skiadopoulos and Panos Kalnis} } @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} } @conference {DBLP:conf/ssdbm/AlGhamdiJSK17, title = {A Benchmark for Betweenness Centrality Approximation Algorithms on Large Graphs}, booktitle = {Proceedings of the 29th International Conference on Scientific and Statistical Database Management, Chicago, IL, USA, June 27-29, 2017}, year = {2017}, pages = {6:1{\textendash}6:12}, doi = {10.1145/3085504.3085510}, url = {https://doi.org/10.1145/3085504.3085510}, author = {Ziyad AlGhamdi and Fuad Jamour and Spiros Skiadopoulos and Panos Kalnis} } @conference {bourlakos-ikc17, title = {Formalization and visualization of the narrative for museum guides}, booktitle = {Proceedings of the third International KEYSTONE Conference (IKC2017)}, year = {2017}, month = {09}, publisher = {Springer}, organization = {Springer}, abstract = {There is a wide range of meta-data standards for the documentation of museum related information, such as CIDOC-CRM; these standards focus on the description of distinct exhibits. In contrast, there is a lack of standards for the digitization and documentation of the routes followed and information provided by museum guides. In this work we propose the notion of the narrative, which can be used to model a guided museum visit. We provide a formalization for the narrative so that it can be digitally encoded, and thus preserved, shared, re-used, further developed and exploited, and also propose an intuitive visualization approach.}, doi = {https://doi.org/10.1007/978-3-319-74497-1_1}, url = {https://link.springer.com/chapter/10.1007/978-3-319-74497-1_1}, author = {Ioannis Bourlakos and Manolis Wallace and Angela Antoniou and Costas Vassilakis and Giorgos Lepouras and Anna Vassiliki Karapanagiotou} } @conference {boukoros2017, title = {Modeling Server Workloads for Campus Email Traffic Using Recurrent Neural Networks}, booktitle = {Proceedings of the 24th International Conference on Neural Information Processing (ICONIP 2017)}, year = {2017}, pages = {57{\textendash}66}, publisher = {Springer International Publishing}, organization = {Springer International Publishing}, abstract = {As email workloads keep rising, email servers need to handle this explosive growth while offering good quality of service to users. In this work, we focus on modeling the workload of the email servers of four universities (2 from Greece, 1 from the UK, 1 from Australia). We model all types of email traffic, including us-er and system emails, as well as spam. We initially tested some of the most popu-lar distributions for workload characterization and used statistical tests to evaluate our findings. The significant differences in the prediction accuracy results for the four datasets led us to investigate the use of a Recurrent Neural Network (RNN) as time series modeling to model the server workload, which is a first for such a problem. Our results show that the use of RNN modeling leads in most cases to high modeling accuracy for all four campus email traffic datasets.}, keywords = {Email traffic, Model server workload, Recurrent neural network, Time series modeling}, doi = {10.1007/978-3-319-70139-4_6}, author = {Spyros Boukoros and Anupiya Nugaliyadde and Angelos Marnerides and Costas Vassilakis and Polychronis Koutsakis and Kok Wai Wong} } @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} } @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 {DBLP:conf/bigdataconf/Chatzigeorgakidis15, title = {A MapReduce based k-NN joins probabilistic classifier}, booktitle = {2015 IEEE International Conference on Big Data, Big Data 2015, Santa Clara, CA, USA, October 29 - November 1, 2015}, year = {2015}, pages = {952{\textendash}957}, doi = {10.1109/BigData.2015.7363844}, url = {https://doi.org/10.1109/BigData.2015.7363844}, author = {Georgios Chatzigeorgakidis and Sophia Karagiorgou and Spiros Athanasiou and Spiros Skiadopoulos} } @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} } @article {DBLP:journals/pvldb/ElseidyASK14, title = {GRAMI: Frequent Subgraph and Pattern Mining in a Single Large Graph}, journal = {PVLDB}, volume = {7}, number = {7}, year = {2014}, pages = {517{\textendash}528}, doi = {10.14778/2732286.2732289}, url = {http://www.vldb.org/pvldb/vol7/p517-elseidy.pdf}, author = {Mohammed Elseidy and Ehab Abdelhamid and Spiros Skiadopoulos and Panos Kalnis} } @proceedings {DBLP:conf/edbt/2014, title = {Proceedings of the 17th International Conference on Extending Database Technology, EDBT 2014, Athens, Greece, March 24-28, 2014}, year = {2014}, publisher = {OpenProceedings.org}, url = {http://openproceedings.org/html/pages/2014_edbt.html}, editor = {Sihem Amer-Yahia and Vassilis Christophides and Anastasios Kementsietsidis and Minos N. Garofalakis and Stratos Idreos and Vincent Leroy} } @conference {lep14a, title = {Towards a Learning Analytics Platform for Supporting the Educational Process}, booktitle = {Proceedings of the 5th Conference on Information, Intelligence, Systems \& Application (IISA2014)}, year = {2014}, month = {7}, abstract = {In this paper, we present the vision of an open source learning analytics platform, able to harvest data from different sources, including e-learning platforms and environments, registrar{\textquoteright}s information systems, alumni systems, etc., so as to provide all stakeholders with the necessary functionality to make decisions on the learning process. The platform{\textquoteright}s architecture is modular, allowing the introduction of new functionality or connection to new systems to collect needed data. All data can be analyzed and presented though interactive visualizations to find correlations between metrics, to make predictions for students or student groups, to identify best practices for instructors and let them explore {\textquoteright}what-if{\textquoteright} scenarios, to offer students personalized recommendations and personalized detailed feedback, etc. Our objective is to inform and empower all stakeholders to improve the learning experience.}, doi = {10.1109/IISA.2014.6878750}, url = {http://ieeexplore.ieee.org/document/6878750/}, author = {Giorgos Lepouras and Akrivi Katifori and Costas Vassilakis and Angela Antoniou and Nikos Platis} } @conference {Katif2014a, title = {Visualization method effectiveness in ontology-based information retrieval tasks involving entity evolution}, booktitle = {Proceedings of SMAP 2014}, year = {2014}, month = {11}, 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 the effectiveness of current ontology browsing and visualization methods for supporting users in tasks involving research on entity evolution.}, doi = {10.1109/SMAP.2014.24}, author = {Akrivi Katifori and Costas Vassilakis and Giorgos Lepouras and C. Halatsis} } @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 {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} } @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} } @proceedings {DBLP:conf/pkdd/2013-3, title = {Machine Learning and Knowledge Discovery in Databases - European Conference, ECML PKDD 2013, Prague, Czech Republic, September 23-27, 2013, Proceedings, Part III}, volume = {8190}, year = {2013}, publisher = {Springer}, isbn = {978-3-642-40993-6}, doi = {10.1007/978-3-642-40994-3}, url = {https://doi.org/10.1007/978-3-642-40994-3}, editor = {Hendrik Blockeel and Kristian Kersting and Siegfried Nijssen and Filip Zelezn{\'y}} } @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-1109-6884, title = {ERA: Efficient Serial and Parallel Suffix Tree Construction for Very Long Strings}, journal = {CoRR}, volume = {abs/1109.6884}, year = {2011}, url = {http://arxiv.org/abs/1109.6884}, author = {Essam Mansour and Amin Allam and Spiros Skiadopoulos and Panos Kalnis} } @article {DBLP:journals/pvldb/MansourASK11, title = {ERA: Efficient Serial and Parallel Suffix Tree Construction for Very Long Strings}, journal = {PVLDB}, volume = {5}, number = {1}, year = {2011}, pages = {49{\textendash}60}, doi = {10.14778/2047485.2047490}, url = {http://www.vldb.org/pvldb/vol5/p049_essammansour_vldb2012.pdf}, author = {Essam Mansour and Amin Allam and Spiros Skiadopoulos and Panos Kalnis} } @conference {Akim2011a, title = {Spreading Activation for Web Scale Reasoning: Promise and Problems}, booktitle = {WebSci 11, poster presentation}, year = {2011}, month = {6}, pages = {1-4}, abstract = {Various forms of spreading activation has been used in a number of web systems, not least in the PageRank algorithm. In our own work we have been using this as a technique for managing context over small and large ontologies, and both our own work and that in LarKC suggests that spreading activation has the potential to aid in reasoning over web-scale data sets including the growing set of linked open data resources. Of particular importance is that spreading activation can be applied locally to a dynamic selfselecting working set of an (practically) unbound linked data collection, as well as globally to the entire collection. However, this potential does not come without problems, some concerning the nature of the algorithm on any large data set, and some more to do with the particular nature of linked open data.}, author = {Nazihah Md. Akim and Alan Dix and Akrivi Katifori and Giorgos Lepouras and Nadeem Shabir and Costas Vassilakis} } @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 {Katifori10a, title = {Ontologies and the brain: Using spreading activation through ontologies to support personal interaction}, journal = {Cognitive Systems Research}, volume = {Volume 11, Issue 1}, year = {2010}, note = {cited By (since 1996) 0; Article in Press}, pages = {25-41}, abstract = {Ontologies, as knowledge engineering tools, allow information to be modelled in ways resembling to those used by the human brain, and may be very useful in the context of personal information management (PIM) and task information management (TIM). This work proposes the use of ontologies as a long-term knowledge store for PIM-related information, and the use of spreading activation over ontologies in order to provide context inference to tools that support TIM. Details on the ontology creation and content are provided, along with a full description of the spreading activation algorithm and its preliminary evaluation. Β{\textcopyright} 2009 Elsevier B.V.}, doi = {10.1016/j.cogsys.2009.02.001}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-62249112875\&partnerID=40\&md5=7d25fb986738b4c71a627b3fec24c58d}, author = {Akrivi Katifori and Costas Vassilakis and Alan Dix} } @article {dix2010, title = {Spreading Activation Over Ontologies: From Personal Context To Web Scale Reasoning}, journal = {International Journal of Semantic Computing}, volume = {Special issue on Web Scale Reasoning}, year = {2010}, pages = {59{\textendash}102}, abstract = {This paper describes methods to allow spreading activation to be used on web-scale information resources. Existing work has shown that spreading activation can be used to model context over small personal ontologies, which can be used to assist in various user activities, for example, in autocompleting web forms. This previous work is extended and methods are developed by which large external repositories, including corporate information and the web, can be linked to the user?s personal ontology and thus allow automated assistance that is able to draw on the entire web of data. The basic idea is augment the personal ontology with cached data from external repositories, where the choice of what data to fetch or discard is related to the level of activation of entities already in the personal ontology or cached data. This relies on the assumption that the working set of highly active entities is relatively small; empirical results are presented, which suggest these assumptions are likely to hold. Implications of the techniques are discussed for user interaction and for the social web. In addition, warm world reasoning is proposed, applying rule-based reasoning over activate entities, potentially merging symbolic and sub-symbolic reasoning over web-scale knowledge bases.}, doi = {10.1142/S1793351X10000973}, author = {Alan Dix and Akrivi Katifori and Giorgos Lepouras and Costas Vassilakis and Nadeem Shabir} } @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} } @inbook {benou2009a, title = {Encyclopedia of Information Science and Technology, Second Edition}, year = {2009}, pages = {1-7}, publisher = {IGI Global}, organization = {IGI Global}, chapter = {Exploiting Context in Mobile Applications}, abstract = {In the mobile and pervasive computing environment, software engineering should not treat diversity and mobility as problems to overcome, but seek methods of which it could take advantage instead. In these environments, the selection of purpose-oriented and timely information, tailored to user preferences and media characteristics will ensure an optimised information delivery. To this end, the context .the information that surrounds the human-computer interaction. plays a key role and is rapidly changing in mobile settings, and the understanding of it is indispensable for the application designers in order to choose, capture and exploit it. In this work, we present an architecture facilitating the collection of context information and its exploitation for optimized information delivery, within mobile and pervasive computing environments.}, doi = {10.4018/978-1-60566-026-4.ch236}, url = {https://www.igi-global.com/chapter/exploiting-context-mobile-applications/13774}, author = {Poulcheria Benou and Costas Vassilakis}, editor = {Mehdi Khosrow-Pour} } @conference {vas2009d, title = {A framework for adaptation in secure web services}, booktitle = {Proceedings of MCIS 2009}, year = {2009}, month = {9}, abstract = {In the context of service-oriented computing, the introduction of the Quality-of-Service (QoS) aspect leads to the need to adapt the execution of programs to the QoS requirements of the particular execution. This is typically achieved by finding alternate services that are functionally equivalent to the ones originally specified in the program and whose QoS characteristics closely match the requirements, and invoking the alternate services instead of the originally specified ones; the same approach can also be employed for tackling exceptions. The techniques proposed insofar, however, cannot be applied in a secure context, where data are encrypted and signed for the originally intended recipient. In this paper, we introduce a framework for facilitating adaptation in the context of secure SOA.}, author = {Costas Vassilakis and Christos Kareliotis} } @article {Vassilakis2009325, title = {A heuristics-based approach to reverse engineering of electronic services}, journal = {Information and Software Technology}, volume = {51}, number = {2}, year = {2009}, note = {cited By (since 1996) 1}, pages = {325-336}, abstract = {Since the beginning of the electronic era, public administrations and enterprises have been developing services, through which citizens, businesses and customers can conduct their transactions with the offering entity. Each electronic service contains a substantial amount of knowledge in the form help texts, rules of use or legislation excerpts, examples, validation checks, etc. This knowledge has been extracted from domain experts when the services were developed, especially in the phases of analysis and design, and was subsequently translated into software. In the latter format though, knowledge cannot be readily used in organizational processes, such as knowledge sharing and development of new services. In this paper, we present an approach for reverse engineering electronic services in order to create knowledge items of high levels of abstraction, which can be used in knowledge sharing environments as well as in service development platforms. The proposed approach has been implemented and configured to generate artifacts for the SmartGov service development platform. Finally, an evaluation of the proposed approach is presented to assess its efficiency regarding various aspects of the reverse engineering process. Β{\textcopyright} 2008 Elsevier B.V. All rights reserved.}, keywords = {Analysis and designs, Domain experts, e-government, electronic services, Government data processing, Help texts, In services, Knowledge engineering, Knowledge sharing, Levels of abstractions, Management, New services, Organizational knowledge, Organizational processes, Public administrations, Reengineering, Reverse engineering, Reverse engineering processes, Service developments, Validation checks}, doi = {10.1016/j.infsof.2008.04.003}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-56949100815\&partnerID=40\&md5=223ff82eddd9005b8e6f7fac1aa9c810}, author = {Costas Vassilakis and Giorgos Lepouras and Akrivi Katifori} } @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 {Kareliotis2009284, title = {IQoS-aware exception resolution for BPEL processes: A middleware-based framework and performance evaluation}, journal = {International Journal of Web and Grid Services}, volume = {5}, number = {3}, year = {2009}, note = {cited By (since 1996) 0}, pages = {284-320}, abstract = {Web Services Business Process Execution Language (WS-BPEL) is widely used nowadays for specifying and executing composite business processes. During the execution, however, of such business processes, a number of faults stemming from the nature of SOA may occur. The WS-BPEL scenario designer must therefore use the provisions offered by WS-BPEL to catch these exceptions and resolve them. The system fault handler specification, however, is an additional task for the WS scenario designer, while the presence of such handlers within the scenario necessitates extra maintenance activities. In this paper, we propose a middleware-based framework for system exception resolution, which undertakes the tasks of failure interception, discovery of alternative services and their invocation. The process of selecting the alternative services can be driven by process consumer-specified Quality of Service (QoS) policy. Moreover, the middleware arranges for bridging syntactic differences between the originally invoked services and functionally equivalent replacements to it, by employing XSLT-based transformations. The middleware is deployed and maintained independently of the WS-BPEL scenarios, thus removing the need for specifying and maintaining system fault handlers within the scenarios. We also present performance measures, establishing that the overhead imposed by the addition of the proposed middleware layer is minimal. Copyright Β{\textcopyright} 2009, Inderscience Publishers.}, keywords = {Ad hoc networks, BPEL process, Exception handling, Exception resolution, Middleware, Performance metrics, QoS, Quality control, Quality of service, Scalability, Telecommunication services, Web services}, doi = {10.1504/IJWGS.2009.028346}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-70349462474\&partnerID=40\&md5=4511b42fde076617cd6ac0139e3f588d}, author = {Christos Kareliotis and Costas Vassilakis and S. Rouvas and P. Georgiadis} } @conference {Christos2009271, title = {QoS-driven adaptation of BPEL scenario execution}, booktitle = {2009 IEEE International Conference on Web Services, ICWS 2009}, year = {2009}, note = {cited By (since 1996) 0}, month = {7}, pages = {271-278}, abstract = {BPEL/WSBPEL is the predominant approach for combining individual web services into integrated business processes, allowing for the specification of their sequence, control flow and data exchanges. BPEL however does not include mechanisms for considering the invoked services{\textquoteright} Quality of Service (QoS) parameters and thus BPEL scenarios can neither tailor their execution to the individual user{\textquoteright}s needs or adapt to the highly dynamic environment of the WEB, where new services may be deployed, old ones withdrawn or existing ones changing their QoS parameters. Moreover, infrastructure failures in the distributed environment of the web introduce an additional source of failures that must be considered in the context of QoS-aware service execution. In this work we propose a framework for addressing the issues identified above; the framework allows the users to specify the QoS parameters that they require and it undertakes the task of locating and invoking suitable services. Finally, the proposed framework intercepts and resolves faults occurring during service invocation, respecting the QoS restrictions specified by the consumer. Β{\textcopyright} 2009 IEEE.}, keywords = {Adaptive execution, BPEL, Control flows, Data exchange, Distributed environments, Dynamic environments, Infrastructure failures, Integrated business, New services, Performance evaliation, QoS parameters, Quality of service, Quality of Service parameters, Service execution, Service invocation, Web services}, doi = {10.1109/ICWS.2009.80}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-70449472686\&partnerID=40\&md5=5303ebeff04a4e7a062f77209521d561}, author = {Christos Kareliotis and Costas Vassilakis and S. Rouvas and P. Georgiadis} } @article {DBLP:journals/tkde/KantereSS09, title = {Storing and Indexing Spatial Data in P2P Systems}, journal = {IEEE Trans. Knowl. Data Eng.}, volume = {21}, number = {2}, year = {2009}, pages = {287{\textendash}300}, doi = {10.1109/TKDE.2008.139}, url = {https://doi.org/10.1109/TKDE.2008.139}, author = {Verena Kantere and Spiros Skiadopoulos and Timos K. Sellis} } @conference {golem2009b, title = {Visualizing Hierarchies: Evaluating the Efficiency and Cognitive Effects of Six Visualization Techniques for Browsing and Management Tasks}, booktitle = {Information Visualization 2009, book of abstracts}, year = {2009}, month = {7}, abstract = {Hierarchical data structures are one of the most commonly used data structures in computer science, and therefore numerous methods and techniques have been proposed for their visualization. In this paper, we present our findings from a user study, in which a number of folder visualization environments were evaluated to assess (a) how efficiently a number of tasks can be performed within the different environments (b) the extent to which using a particular visualization may help the user acquire an accurate cognitive image of the hierarchy structure and its contents and (c) the overall user experience from using a particular visualization environment. The visualization environments considered are representative of major visualization paradigms (zoomable user interfaces, context+focus and space-filling), while both 2D and 3D environments have been included.}, author = {M. Golemati and Costas Vassilakis and Akrivi Katifori and Giorgos Lepouras and C. Halatsis} } @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} } @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 {daradim2008, title = {A Drupal CMS Module for Managing Museum Collections}, booktitle = {International Symposium on Information \& communication technologies in cultural heritage}, year = {2008}, month = {10}, abstract = {Digitization efforts and web presentations are currently on-going in many museums, archives, libraries and culture heritage institutions in general, exploiting the advent of WWW and digitization technologies. The main benefits from these efforts are exhibit cataloguing, their effective management, preservation and showcasing, and their presentation to the public through the WWW. However, many museums, especially the smaller ones, cannot afford a commercial product and resort to using simple static web pages for their web presence and exhibit presentation. Content Management Systems (CMS), especially open-source ones which come with practically zero-cost, are more and more frequently adopted by museums to create and maintain their website, since they simplify the creation and editing of the web pages and may be used by non-computer experts. In this work we present a module for the Drupal CMS, which provides functionality for (a) Database schema extension to accommodate museum exhibit and collection information (b) Digital exhibit representation (DER) management. (c) Provision of administration pages through which the museum personnel may enter and manage exhibit and collection information (d) WWW scowcasing and (e) Batch data import/export, to facilitate information exchange with other museums.}, author = {I. Daradimos and Costas Vassilakis and Akrivi Katifori} } @conference {Christos2008248, title = {Exception resolution for BPEL processes: A middleware-based framework and performance evaluation}, booktitle = {Proceedings of the 10th International Conference on Information Integration and Web-based Applications and Services, iiWAS 2008}, year = {2008}, note = {cited By (since 1996) 0}, month = {12}, pages = {248-256}, abstract = {WS-BPEL is widely used nowadays for specifying and executing composite business processes within the Service Oriented Architecture (SOA). During the execution however, of such business processes, a number of faults stemming from the nature of SOA (e.g. network or server failures) may occur. The WS-BPEL scenario designer must therefore use the provisions offered by WS-BPEL to catch these exceptions and resolve them, usually by invoking some equivalent web service that is expected to be reachable and available. System fault handler specification is though an additional task for the WS scenario designer, while the presence of such handlers within the scenario necessitates extra maintenance activities, as new alternate services emerge or some of the specified ones are withdrawn. In this paper, we propose a middleware-based framework for system exception resolution, which undertakes the tasks of failure interception, discovery of alternate services and their invocation. The middleware is deployed and maintained independently of the WS-BPEL scenarios, removing thus the need for specifying and maintaining system fault handlers within the scenarios. We also present performance measures, establishing that the overhead imposed by the addition of the proposed middleware layer is minimal. Β{\textcopyright} 2008 ACM.}, keywords = {Ad hoc networks, Business Process, Exception handling, Information retrieval, Information services, Maintenance activity, Middleware, Middleware layer, Performance evaluation, Performance measure, Performance metrics, Quality control, Quality of service, Quality of service (QoS), Scalability, Service oriented architecture (SOA), System faults, Telecommunication services, Web services, WS-BPEL}, doi = {10.1145/1497308.1497355}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-70349146138\&partnerID=40\&md5=9a5231fe52fffef11707efd4f3489a37}, author = {Christos Kareliotis and Costas Vassilakis and S. Rouvas and P. Georgiadis} } @article {vas2008d, title = {An Integrated Environment for Cataloguing and Online Presentation of Museum Exhibits}, journal = {DESIDOC Journal of Library and Information Technology}, volume = {28(4)}, year = {2008}, pages = {72-78}, abstract = {The paper presents an integrated environment which enables museum personnel to catalogue and at the same time publish online museum exhibits. The system is based on international standards and is highly customisable to cater the needs of a variety of museum types. Moreover, the underlying database allows storing for the same exhibit documentations for different audiences and in multiple languages, while it is extendable to accommodate new media types, languages, exhibits and information categories. The administrative part of the environment permits the restriction of certain functions to specific personnel roles, enforcing thus a general museum security policy regarding access to and modification of information. The environment presented is currently in use at the Athens University History Museum.}, author = {Costas Vassilakis and Akrivi Katifori and I. Daradimos and Giorgos Lepouras} } @inbook {gol2009a, title = {Intelligent User Interfaces: Adaptation and Personalization Systems and Technologies}, year = {2008}, pages = {188{\textendash}204}, publisher = {IGI Publishing}, organization = {IGI Publishing}, chapter = {Context and Adaptivity-Driven Visualization Method Selection}, abstract = {Novel and intelligent visualization methods are being developed in order to accommodate user searching and browsing tasks, including new and advanced functionalities. Besides, research in the field of user modeling is progressing in order to personalize these visualization systems, according to its users{\textquoteright} individual profiles. However, employing a single visualization system, may not suit best any information seeking activity. In this paper we present a visualization environment, which is based on a visualization library, i.e. is a set of visualization methods, from which the most appropriate one is selected for presenting information to the user. This selection is performed combining information extracted from the context of the user, the system configuration and the data collection. A set of rules inputs such information and assigns a score to all candidate visualization methods. The presented environment additionally monitors user behavior and preferences to adapt the visualization method selection criteria.}, author = {M. Golemati and Costas Vassilakis and Akrivi Katifori and Giorgos Lepouras and C. Halatsis}, editor = {C. Mourlas and P. Germanakos} } @conference {Golemati2008106, title = {An interview-based user study on the use of visualizations for folder browsing}, booktitle = {Proceedings of the International Conference on Information Visualisation}, year = {2008}, note = {cited By (since 1996) 0}, month = {7}, pages = {106-112}, abstract = {Hierarchically structured data collections often need to be visualized for the purposes of digital information management and presentation. File browsing, in particular, has an inherent hierarchical structure and plays an important role in the context of Personal Information Management (PIM). A multitude of file browsers are nowadays available, offering different functionalities, while users adopt diverse practices and habits for browsing activities. In this paper, we investigate these aspects to obtain insights into their advantages and disadvantages and suggest solutions in the area of PIM, as well as in other domains employing similar visualization paradigms. The presented study focuses on the two most widespread visualizations used by file browsers, the indented list and zoomable interface paradigms, and assesses their effectiveness for various tasks and contexts, both by exploiting results on existing evaluations on hierarchy visualizations and folder hierarchy visualizations in particular, and by conducting an interviewbased user study. Β{\textcopyright} 2008 IEEE.}, keywords = {Administrative data processing, File browser visualization, Indented list visualization, Information analysis, Information management, Information science, Intermodulation, Intermodulation measurement, International conferences, Management, Management information systems, Telecommunication services, User study, Windows explorer}, doi = {10.1109/IV.2008.90}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-51749097531\&partnerID=40\&md5=66afc30e74191773d1c950ac83ba9ac7}, author = {M. Golemati and Akrivi Katifori and E.G. Giannopoulou and I. Daradimos and Costas Vassilakis and Giorgos Lepouras and C. Halatsis} } @conference {katifori2008e, title = {Ontologies as Tools for Historians}, booktitle = {International Symposium on Information \& communication technologies in cultural heritage}, year = {2008}, month = {10}, abstract = {Ontologies have been proven invaluable tools in areas like the semantic web and personal information management. There have been many research efforts to create ontologies and supporting tools for Natural Sciences and Biology in particular (e.g. the GO (http://www.geneontology.org/) ontology and supporting tools). However, the domain of History, the science of studying, recording and organizing the knowledge of the past, has yet to benefit from adopting ontologies. In this work, we present our findings in this area, focusing on the aspects of ontology modeling and ontology visualization.}, author = {Akrivi Katifori and Costas Vassilakis} } @conference {Vasiliadis200890, title = {Performance Evaluation of Distance Vector Routing Protocol on a Wireless Circular Model}, booktitle = {Proceedings of the IEEE sponsored International Joint Conference CISSE 2007}, year = {2008}, month = {12}, pages = {323-328}, publisher = {Springer Netherlands}, organization = {Springer Netherlands}, abstract = {In this paper, a wireless Circular Model over a generic distance-vector routing protocol is presented and analyzed. The performance of this model over the Distance Vector protocol, which is an implementation of Distributed Bellman-Ford algorithm, has been evaluated by using the simulation environment of NS-2. We conducted an extensive evaluation study for various mobility schemes in order to incorporate the behavior of nodes and the routing protocol in a real-life hotspot situation In the test-bed model, while the number of source nodes was allowed to arbitrarily vary, there was exactly one destination node, closely modeling thus real-life situations where a single hotspot/access point exists. Finally, different constant bit rates (CBR) were used in order to estimate the throughput of receiving, dropping rates, the number of lost packets, as well as the average packet delay under various traffic conditions. This study is aimed to help wireless network designers in choosing the best suited routing protocols for their networks, through making explicit performance figures for common network setups.}, doi = {10.1007/978-1-4020-8737-0}, author = {D.C. Vasiliadis and G.E. Rizos and Costas Vassilakis}, editor = {Tarek Sobh and Khaled Elleithy and Ausif Mahmood and Mohammad A. Karim} } @conference {Katifori2008a1, title = {Personal Ontology Creation and Visualization for a Personal Interaction Management System}, booktitle = {Proceedings of PIM, CHI 2008}, year = {2008}, month = {4}, abstract = {Ontologies offer a flexible and expressive layer of abstraction, very useful for capturing the semantics of information repositories and facilitating their retrieval either by the user or by the system to support user tasks. This work presents an ontology-based user profiler, in the context of a Personal Interaction Management System (PIMS). The profiler, based on an ontology of the users? domain, enables them to create their personal ontology by initially choosing one of the available template ontologies as a starting point, which they subsequently populate and customize. The profiler employs a web interface which allows users to populate their personal ontology through forms, hiding ontology complexities and peculiarities. Forms are dynamically generated through ontology views, which are specified by ontology designers.}, author = {Akrivi Katifori and Costas Vassilakis and I. Daradimos and Giorgos Lepouras and Yannis Ioannidis and Alan Dix and Antonella Poggi and Tiziana Catarci} } @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} } @conference {katifori2008b, title = {Using Spreading Activation through Ontologies to Support Personal Information Management}, booktitle = {Proceedings of CSKGOI, within IUI 2008}, year = {2008}, month = {1}, abstract = {Recent research in the domain of Personal Information Management has recognized the need for a paradigm shift towards a more activity-oriented system. Ontologies, as semantic networks with a structure not dissimilar to the one used by the human brain for storing long-term knowledge, may be very useful as the basis of such a system. This work proposes the use of spreading activation over ontologies in order to provide to a task-based system and its associated tools with methods to record semantics related to documents and tasks and to support user context inference.}, url = {http://ceur-ws.org/Vol-323/paper05.pdf}, author = {Akrivi Katifori and Costas Vassilakis and Alan Dix} } @conference {Daradimos2008141, title = {WhereRU: GPS position reporting and a personal ontology as a virtual community utility}, 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 = {141-146}, abstract = {The recent progress of the World Wide Web has created new needs for information sharing in virtual communities. WhereRU is a multiuser GPS position reporting system that allows users to make their location publicly available as well as associate it with information on places, persons and events that may later also serve as reminders of the their experiences when traveling.}, keywords = {Communication, Global positioning system, Gps positions, Information science, Information sharing, Internet, Multiuser, Ontology, Personal ontologies, Position reporting, Recent progresses, Reporting systems, Satellite navigation aids, Virtual communities, Virtual reality, Web community, World Wide Web}, doi = {10.1109/RCIS.2008.4632102}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-57349094004\&partnerID=40\&md5=4eaed4757acf5c4da8b292275b92a73a}, author = {I. Daradimos and Akrivi Katifori and Costas Vassilakis} } @proceedings {DBLP:conf/ssd/2007, title = {Advances in Spatial and Temporal Databases, 10th International Symposium, SSTD 2007, Boston, MA, USA, July 16-18, 2007, Proceedings}, volume = {4605}, year = {2007}, publisher = {Springer}, isbn = {978-3-540-73539-7}, doi = {10.1007/978-3-540-73540-3}, url = {https://doi.org/10.1007/978-3-540-73540-3}, editor = {Dimitris Papadias and Donghui Zhang and George Kollios} } @conference {kalikakis2007b, title = {An Approach for re-engineering the Taxation Process to Support Participatory Decisions on Tax Budget Allocation}, booktitle = {Proceedings of the 1st International Conference on Methodologies, Technologies and Tools enabling e-Government}, year = {2007}, month = {9}, abstract = {The tax collection process has been described as a bureaucratic one, that confines citizen involvement to the role of passive fulfillment of administrative and financial obligations. Active citizen participation, in the form of some political say on the allocation of collected taxes which could potentially improve and further legitimize tax collection, is not a part of the traditional taxation model. In this paper we describe a new taxation model which, in the spirit of participatory budgeting approaches, supports active citizens? participation on decision making regarding tax funds allocation.}, author = {M. Kalikakis and D. Gouscos and Costas Vassilakis and P. Georgiadis} } @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} } @article {DBLP:journals/tkde/SkiadopoulosSSK07a, title = {Correction to "A Family of Directional Relation Models for Extended Objects"}, journal = {IEEE Trans. Knowl. Data Eng.}, volume = {19}, number = {10}, year = {2007}, pages = {1448}, doi = {10.1109/TKDE.2007.190653}, url = {https://doi.org/10.1109/TKDE.2007.190653}, author = {Spiros Skiadopoulos and Nikos Sarkas and Timos K. Sellis and Manolis Koubarakis} } @conference {KatiforiGVLH07, title = {Creating an Ontology for the User Profile: Method and Applications}, booktitle = {RCIS}, year = {2007}, month = {4/2007}, pages = {407{\textendash}412}, abstract = {User profiling is commonly employed nowadays to enhance usability as well as to support personalization, adaptivity and other user-centric features. Insofar, application designers model user profiles mainly in an ad-hoc manner, hindering thus application interoperability at the user profile level, increasing the amount of work to be done and the possibility of errors or omissions in the profile model. This work aims at creating a user profile ontology that incorporates concepts and properties used to model the user profile. Existing literature, applications and ontologies related to the domain of user context and profiling have been taken into account in order to create a general, comprehensive and extensible user model. This ontology can be used as a reference model, in order to alleviate the aforementioned issues. The model, available for download, is exemplified through its application in two different areas, personal information management and adaptive visualization.}, author = {Akrivi Katifori and M. Golemati and Costas Vassilakis and Giorgos Lepouras and C. Halatsis} } @conference {DBLP:conf/icws/KareliotisVG07, title = {Enhancing BPEL scenarios with Dynamic Relevance-Based Exception Handling}, booktitle = {ICWS}, year = {2007}, month = {7}, pages = {751-758}, abstract = {Web services have become the key technology in business processes management. Business processes can be self-contained or be composed from sub-processes; the latter category is typically specified using the Web Services Business Process Execution Language (WS-BPEL) and executed by a Web Services Orchestrator (WSO). During the execution however of such a composite service, a number of faults stemming from the distributed nature of the SOA architecture, e.g. network or server failures may occur. WS-BPEL includes provisions for exception handling, which can be exploited for detecting such failures; once detected, a failure can be resolved by invoking alternate web service implementations that perform the same business task as the failed one. However, the inclusion of such provisions is a tedious assignment for the business process designer, while additional effort would be required to maintain the BPEL scenarios in cases that some alternate WS implementations cease to exist or new ones are introduced. In our research we are developing a framework for automating handling of that kind of exceptions. The proposed solution employs a pre-processor that enhances BPEL scenarios with code that detects failures, discovers alternate WS implementations and invokes them, fully thus resolving the exception. Alternate WS implementation discovery is based on service relevance, which takes into account both functional and qualitative properties of web services.}, doi = {10.1109/ICWS.2007.86}, author = {Christos Kareliotis and Costas Vassilakis and P. Georgiadis} } @conference {Golemati200793, title = {Evaluating the significance of the windows explorer visualization in personal information management browsing tasks}, booktitle = {Proceedings of the International Conference on Information Visualisation}, year = {2007}, note = {cited By (since 1996) 0}, month = {7}, pages = {93-98}, abstract = {The visualization of hierarchies is very important for digital information management and presentation systems. Especially in the context of Personal Information Management, file browsers play a very important role. Currently the most common file browser visualizations are Windows Explorer and the simple zoomable visualization offered by Microsoft Windows. This work explores the issue of file browser visualization through a user study based on inter-views and an experiment. Β{\textcopyright} 2007 IEEE.}, keywords = {Data reduction, File browser visualization, Hierarchical systems, Indented list visualization, Information analysis, User study, Web browsers, Windows explorer}, doi = {10.1109/IV.2007.46}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-35348919670\&partnerID=40\&md5=f35f306d4063ee2e91e3c573f4ed5d8a}, author = {M. Golemati and Akrivi Katifori and E.G. Giannopoulou and I. Daradimos and Costas Vassilakis} } @article {DBLP:journals/tkde/SkiadopoulosSSK07, title = {A Family of Directional Relation Models for Extended Objects}, journal = {IEEE Trans. Knowl. Data Eng.}, volume = {19}, number = {8}, year = {2007}, pages = {1116{\textendash}1130}, doi = {10.1109/TKDE.2007.1046}, url = {https://doi.org/10.1109/TKDE.2007.1046}, author = {Spiros Skiadopoulos and Nikos Sarkas and Timos K. Sellis and Manolis Koubarakis} } @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 {DBLP:conf/ssd/GhinitaKS07, title = {MobiHide: A Mobilea Peer-to-Peer System for Anonymous Location-Based Queries}, booktitle = {Advances in Spatial and Temporal Databases, 10th International Symposium, SSTD 2007, Boston, MA, USA, July 16-18, 2007, Proceedings}, year = {2007}, pages = {221{\textendash}238}, doi = {10.1007/978-3-540-73540-3_13}, url = {https://doi.org/10.1007/978-3-540-73540-3_13}, author = {Gabriel Ghinita and Panos Kalnis and Spiros Skiadopoulos} } @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} } @article {Katifori2007, title = {Ontology visualization methods - A survey}, journal = {ACM Computing Surveys}, volume = {39}, number = {4}, year = {2007}, note = {cited By (since 1996) 21}, pages = {10:1-10:43}, abstract = {Ontologies, as sets of concepts and their interrelations in a specific domain, have proven to be a useful tool in the areas of digital libraries, the semantic web, and personalized information management. As a result, there is a growing need for effective ontology visualization for design, management and browsing. There exist several ontology visualization methods and also a number of techniques used in other contexts that could be adapted for ontology representation. The purpose of this article is to present these techniques and categorize their characteristics and features in order to assist method selection and promote future research in the area of ontology visualization. Β{\textcopyright} 2007 ACM.}, keywords = {Digital libraries, Human computer interaction, Information management, Ontology, Ontology representation, Ontology visualization, Personalized information management, Semantic Web, visualization methods}, doi = {10.1145/1287620.1287621}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-36048959880\&partnerID=40\&md5=a74cd76829bee9bb1cc21d6118e65340}, author = {Akrivi Katifori and C. Halatsis and Giorgos Lepouras and Costas Vassilakis and E.G. Giannopoulou} } @conference {DBLP:conf/www/GhinitaKS07, title = {PRIVE: anonymous location-based queries in distributed mobile systems}, booktitle = {Proceedings of the 16th International Conference on World Wide Web, WWW 2007, Banff, Alberta, Canada, May 8-12, 2007}, year = {2007}, pages = {371{\textendash}380}, doi = {10.1145/1242572.1242623}, url = {https://doi.org/10.1145/1242572.1242623}, author = {Gabriel Ghinita and Panos Kalnis and Spiros Skiadopoulos} } @conference {kalikakis2007a, title = {Towards a P2P world: peered taxation}, booktitle = {Proceedings of the 2nd International Workshop "E-taxation: State \& Perspectives"}, year = {2007}, month = {2}, abstract = {This paper presents the current model for taxation and distribution of the taxes to government activities, and an alternative model is presented, according to which tax-payers can determine, to some extent, the way that the taxes they pay will be spent. The goal of this proposal is to increase citizen involvment and system transparency. The model proposal comescomplete with an architecture that supports the realization of the proposed scheme}, author = {M. Kalikakis and D. Gouscos and Costas Vassilakis and P. Georgiadis} } @conference {Vassilakis20071564, title = {Web service execution streamlining}, booktitle = {Proceedings - ICSSSM{\textquoteright}06: 2006 International Conference on Service Systems and Service Management}, volume = {2}, year = {2007}, note = {cited By (since 1996) 0}, month = {10}, pages = {1564-1569}, abstract = {Web services are functional, independent components that can be called over the web to perform a task. Besides being used individually to deliver some well-specified functionality, web services may be used as building blocks that can be combined to implement a more complex function. In such compositions, typically some web services produce results that are used as input for web services that will be subsequently invoked. In the execution schemes currently employed, web services producing intermediate results deliver them to some "coordinating entity", which arranges the forwarding of these intermediate results to web services that require them as input. In this paper we present an execution scheme that employs direct communication between producers and consumers of intermediate results. Besides performance improvement stemming from reduction of network communication, this scheme permits consumer web services to employ simpler authenticity and integrity verification algorithms on incoming parameters. when the producer web service is considered trustworthy. Β{\textcopyright}2006 IEEE.}, keywords = {Algorithms, Function evaluation, Optimization, Parameter estimation, Streamlining, Web service execution, Web service synthesis, Web services}, doi = {10.1109/ICSSSM.2006.320769}, url = {http://ieeexplore.ieee.org/document/4114724/}, author = {Costas Vassilakis and Giorgos Lepouras and Akrivi Katifori} } @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 {Golemati200662, title = {A context-based adaptive visualization environment}, booktitle = {Proceedings of the International Conference on Information Visualisation}, year = {2006}, note = {cited By (since 1996) 0}, month = {7}, pages = {62-67}, abstract = {Digital libraries and historical archives are increasingly employing visualization systems to facilitate the information retrieval and knowledge extraction tasks of their users. Typically, each organization employs a single visualization system, which may not suit best the needs of certain user groups, specific tasks, or properties of document collections to be visualized. In this paper we present a context-based adaptive visualization environment, which embeds a set of visualization methods into a visualization library, from which the most appropriate one is selected for presenting information to the user. Methods are selected by examining parameters related to the user profile, system configuration and the set of data to be visualized, and employing a set of rules to assess the suitability of each method. The presented environment additionally monitors user behavior and preferences to adapt the visualization method selection criteria. Β{\textcopyright} 2006 IEEE.}, keywords = {(PL) properties, Adaptive systems, Adaptive visualization, Behavioral research, Digital libraries, document collections, Extraction, Information analysis, Information science, Information services, Information systems, Information visualization, Knowledge extraction, Libraries, Retrieval (MIR), Search engines, Selection criterion, Set of rules, Solvent extraction, Specific tasks, System configurations, User behaviors, User groups, user profiling, Visualization, visualization methods, Visualization systems}, doi = {10.1109/IV.2006.5}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-45149121827\&partnerID=40\&md5=ec45ad555b132faaf0bd2ca53e3292dc}, author = {M. Golemati and C. Halatsis and Costas Vassilakis and Akrivi Katifori and Giorgos Lepouras} } @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 {lep2006b, title = {Encyclopedia of E-Commerce, E-Government and Mobile Commerce}, year = {2006}, pages = {1{\textendash}6}, publisher = {Idea Group Inc.}, organization = {Idea Group Inc.}, chapter = {Adaptive Virtual Reality Shopping Malls}, abstract = {Firms and organizations are increasingly exploiting electronic channels to reach their customers and create new business opportunities. To this end, electronic shops have been developed, either offering products from a single firm or encompassing multiple individual electronic stores, comprising thus electronic shopping malls. Two main concerns for e-commerce are personalization and enhancement of user experience. Personalization addresses the ability to offer content tailored to the preferences of each user or user group. Preferences may be explicitly declared by the user, or derived by the system through inspecting user interaction; if the system dynamically reacts to changes of visitor behavior, it is termed as adaptive. Enhancement of user experience is another major issue in e-commerce, given that 2D-images and texts on the screen are not sufficient to provide information on products aspects such as physical dimensions, textures and manipulation feedback. Multimedia presentations can also be used as a means for .information acceleration. for promoting "really new" products. This article aims to specify a system that exploits capabilities offered by adaptation and VR technologies to offer e-shoppers personalized and enhanced experiences, while addressing challenges related to the cost, complexity and effort of building and maintaining such a system.}, doi = {10.4018/978-1-59904-955-7.ch099}, author = {Giorgos Lepouras and Costas Vassilakis}, editor = {Mehdi Khosrow-Pour} } @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} } @inbook {vas2006a, title = {Encyclopedia of E-Commerce, E-Government and Mobile Commerce}, year = {2006}, pages = {865{\textendash}870}, publisher = {Idea Group Inc.}, organization = {Idea Group Inc.}, chapter = {Ontology for e-Government public services}, abstract = {In this work, the usage of ontologies for meeting requirements related to e-service composition, e-service cataloguing, change management and administrative responsibility is examined. An ontology for e-government services is presented, covering various aspects of services, including administrative responsibility, meta-data, involved documents and legislation. Both the development and usage phase of the ontology are covered and directions for further exploitation of the potential offered by the ontological representation are given.}, doi = {10.4018/978-1-59140-799-7.ch139}, author = {Costas Vassilakis and Giorgos Lepouras}, 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 {DBLP:conf/icsoft/VassilakisLK06, title = {Reverse engineering electronic services: from e-forms to knowledge}, booktitle = {ICSOFT (1)}, year = {2006}, month = {9}, pages = {273-278}, abstract = {On their route to e-governance, public administrations have developed e-services. Each e-service encompasses a significant amount of knowledge in the form of examples, help texts, legislation excerpts, validation checks etc. This knowledge has been offered by domain experts in the phases of service analysis, design and implementation, being however bundled within the software, it cannot be readily retrieved and used in other organizational processes, including the development of new services. In this paper, we present an approach for reverse engineering e-services, in order to formulate knowledge items of a high level of abstraction, which can be made available to the employees of the organizations. Moreover, the knowledge items formulated in the reverse engineering process are stored into a knowledge-based e-service development platform, making them readily available for use in the development of other services.}, author = {Costas Vassilakis and Giorgos Lepouras and Akrivi Katifori} } @conference {kareliotis2006, title = {Towards Dynamic, Relevance-Driven Exception Resolution in Composite Web Services}, booktitle = {Proceedings of OOPSLA 2006, Fourth International Workshop on SOA \& Web Services Best Practices}, year = {2006}, month = {10}, abstract = {Web services have become the leading technology for application-toapplication (A2A) communication over distributed and heterogeneous environments. Both academia and industry have strived to enable useful service collaborations among distributed systems without any human intervention. Web service composition can be used to this end, to achieve business automation within one company or realize business-to-business (B2B) integration of heterogeneous software and cross-organizational computing systems. Service composition pro-vides added value, when a web service composition itself becomes a higher level composite web service. However, as business processes are long-lasting transactions, exceptions may often occur, necessitating the replacement of a service component which has been made unavailable, hindering the completion of some business process. In this paper we present an exception resolving approach based on discovering replacement components that are functionally equivalent, taking also into account criteria for qualitative substitutability. The proposed solution introduces the Service Relevance and Replacement Framework (SRRF) which undertakes exception handling.}, author = {Christos Kareliotis and Costas Vassilakis and P. Georgiadis} } @conference {1133365, title = {Visualizing a temporally-enhanced ontology}, booktitle = {AVI {\textquoteright}06: Proceedings of the working conference on Advanced visual interfaces}, year = {2006}, month = {5}, pages = {488{\textendash}491}, publisher = {ACM}, organization = {ACM}, address = {New York, NY, USA}, 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 modeling for entity and relationship timelines in the Prot.g. tool, complemented with a visualization plug-in, which enables users to examine entity evolution along the timeline.}, isbn = {1-59593-353-0}, doi = {10.1145/1133265.1133365}, author = {Akrivi Katifori and Costas Vassilakis and Giorgos Lepouras and I. Daradimos and C. Halatsis} } @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} } @article {DBLP:journals/tkde/SkiadopoulosGSVSK05, title = {Computing and Managing Cardinal Direction Relations}, journal = {IEEE Trans. Knowl. Data Eng.}, volume = {17}, number = {12}, year = {2005}, pages = {1610{\textendash}1623}, doi = {10.1109/TKDE.2005.192}, url = {https://doi.org/10.1109/TKDE.2005.192}, author = {Spiros Skiadopoulos and Christos Giannoukos and Nikos Sarkas and Panos Vassiliadis and Timos K. Sellis and Manolis Koubarakis} } @proceedings {DBLP:conf/er/2005, title = {Conceptual Modeling - ER 2005, 24th International Conference on Conceptual Modeling, Klagenfurt, Austria, October 24-28, 2005, Proceedings}, volume = {3716}, year = {2005}, publisher = {Springer}, isbn = {3-540-29389-2}, doi = {10.1007/11568322}, url = {https://doi.org/10.1007/11568322}, editor = {Lois M. L. Delcambre and Christian Kop and Heinrich C. Mayr and John Mylopoulos and Oscar Pastor} } @article {DBLP:journals/ai/SkiadopoulosK05, title = {On the consistency of cardinal direction constraints}, journal = {Artif. Intell.}, volume = {163}, number = {1}, year = {2005}, pages = {91{\textendash}135}, doi = {10.1016/j.artint.2004.10.010}, url = {https://doi.org/10.1016/j.artint.2004.10.010}, author = {Spiros Skiadopoulos and Manolis Koubarakis} } @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} } @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} } @proceedings {DBLP:conf/edbt/2004, title = {Advances in Database Technology - EDBT 2004, 9th International Conference on Extending Database Technology, Heraklion, Crete, Greece, March 14-18, 2004, Proceedings}, volume = {2992}, year = {2004}, publisher = {Springer}, isbn = {3-540-21200-0}, doi = {10.1007/b95855}, url = {https://doi.org/10.1007/b95855}, editor = {Elisa Bertino and Stavros Christodoulakis and Dimitris Plexousakis and Vassilis Christophides and Manolis Koubarakis and Klemens B{\"o}hm and Elena Ferrari} } @article {DBLP:journals/ai/SkiadopoulosK04, title = {Composing cardinal direction relations}, journal = {Artif. Intell.}, volume = {152}, number = {2}, year = {2004}, pages = {143{\textendash}171}, doi = {10.1016/S0004-3702(03)00137-1}, url = {https://doi.org/10.1016/S0004-3702(03)00137-1}, author = {Spiros Skiadopoulos and Manolis Koubarakis} } @conference {DBLP:conf/edbt/SkiadopoulosGVSK04, title = {Computing and Handling Cardinal Direction Information}, booktitle = {Advances in Database Technology - EDBT 2004, 9th International Conference on Extending Database Technology, Heraklion, Crete, Greece, March 14-18, 2004, Proceedings}, year = {2004}, pages = {329{\textendash}347}, doi = {10.1007/978-3-540-24741-8_20}, url = {https://doi.org/10.1007/978-3-540-24741-8_20}, author = {Spiros Skiadopoulos and Christos Giannoukos and Panos Vassiliadis and Timos K. Sellis 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 {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} } @article {1009361, title = {Real exhibitions in a virtual museum}, journal = {Virtual Reality}, volume = {7}, number = {2}, year = {2004}, pages = {120{\textendash}128}, publisher = {Springer-Verlag}, address = {London, UK}, abstract = {When creating a virtual environment open to the public a number of challenges have to be addressed. The equipment has to be chosen carefully in order to be be able to withstand hard every-day usage, the application has not only to be robust and easy to use, but has also to be appealing to the user, etc. The current paper presents findings gathered from the creation of a multi-thematic virtual museum environment to be offered to visitors of real world museums. A number of design and implementation aspects are described along with an experiment designed to evaluate alternative approaches for implementing the navigation in a virtual museum environment. The paper is concluded with insights gained from the development of the Virtual Museum and portrays future research plans.}, issn = {1359-4338}, doi = {10.1007/s10055-004-0121-5}, url = {https://link.springer.com/article/10.1007/s10055-004-0121-5}, author = {Giorgos Lepouras and Akrivi Katifori and Costas Vassilakis and D. Charitos} } @proceedings {DBLP:conf/dawak/2003, title = {Data Warehousing and Knowledge Discovery, 5th International Conference, DaWaK 2003, Prague, Czech Republic, September 3-5,2003, Proceedings}, volume = {2737}, year = {2003}, publisher = {Springer}, isbn = {3-540-40807-X}, doi = {10.1007/b11825}, url = {https://doi.org/10.1007/b11825}, editor = {Yahiko Kambayashi and Mukesh K. Mohania and Wolfram W{\"o}{\ss}} } @conference {lep03a, title = {Facilitating VR Museums Web Presence}, booktitle = {Proceedings of HCI 2003}, year = {2003}, month = {6}, pages = {1143{\textendash}1147}, abstract = {The paper presents an environment that enables museum curators to catalogue and publish on the web exhibits in multiple languages and media including 3D, video, images. The system is extendable to accommodate new media types, languages, exhibits, information categories, etc. Visitors have the potential to formulate dynamic personalised exhibit collections using search mechanisms provided by the system.}, author = {Giorgos Lepouras and Akrivi Katifori and Costas Vassilakis and Anna Charissi} } @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 {DBLP:conf/chorochronos/GrumbachKRSS03, title = {Spatio-temporal Models and Languages: An Approach Based on Constraints}, booktitle = {Spatio-Temporal Databases: The CHOROCHRONOS Approach}, year = {2003}, pages = {177{\textendash}201}, doi = {10.1007/978-3-540-45081-8_5}, url = {https://doi.org/10.1007/978-3-540-45081-8_5}, author = {St{\'e}phane Grumbach and Manolis Koubarakis and Philippe Rigaux and Michel Scholl and Spiros Skiadopoulos} } @conference {DBLP:conf/cp/SkiadopoulosK02, title = {Consistency Checking for Qualitative Spatial Reasoning with Cardinal Directions}, booktitle = {Principles and Practice of Constraint Programming - CP 2002, 8th International Conference, CP 2002, Ithaca, NY, USA, September 9-13, 2002, Proceedings}, year = {2002}, pages = {341{\textendash}355}, doi = {10.1007/3-540-46135-3_23}, url = {https://doi.org/10.1007/3-540-46135-3_23}, author = {Spiros Skiadopoulos and Manolis Koubarakis} } @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} } @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 {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} } @article {DBLP:journals/is/VassiliadisVSKS01, title = {ARKTOS: towards the modeling, design, control and execution of ETL processes}, journal = {Inf. Syst.}, volume = {26}, number = {8}, year = {2001}, pages = {537{\textendash}561}, doi = {10.1016/S0306-4379(01)00039-4}, url = {https://doi.org/10.1016/S0306-4379(01)00039-4}, author = {Panos Vassiliadis and Zografoula Vagena and Spiros Skiadopoulos and Nikos Karayannidis and Timos K. Sellis} } @conference {DBLP:conf/ssd/SkiadopoulosK01, title = {Composing Cardinal Direction Relations}, booktitle = {Advances in Spatial and Temporal Databases, 7th International Symposium, SSTD 2001, Redondo Beach, CA, USA, July 12-15, 2001, Proceedings}, year = {2001}, pages = {299{\textendash}320}, doi = {10.1007/3-540-47724-1_16}, url = {https://doi.org/10.1007/3-540-47724-1_16}, author = {Spiros Skiadopoulos and Manolis Koubarakis} } @conference {Charitos2001284, title = {Designing a virtual museum within a museum}, booktitle = {Proceedings VAST 2001 Virtual Reality, Archeology, and Cultural Heritage}, year = {2001}, note = {cited By (since 1996) 0}, month = {11}, pages = {284}, abstract = {The designing of a virtual museum within a museum was discussed. In regard with it, the Virtual Museum project sponsored by the Greek General Secretariat of Research and Technology was presented. The project{\textquoteright}s main objective was to create a virtual environment (VE) for enhancing the experience of visiting a museum by affording view and manipulation of certain exhibits.}, keywords = {Information retrieval systems, Internet, Museums, Technical presentations, Three dimensional computer graphics, Virtual museum, Virtual reality}, doi = {10.1145/584993.585043}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-0141426770\&partnerID=40\&md5=50066081a4e5d55bfc3c823813535add}, author = {D. Charitos and Giorgos Lepouras and Costas Vassilakis and Akrivi Katifori and Charissi, A. and Halatsi, L.}, editor = {S. N. Spencer} } @conference {Dimitrios00anapproach, title = {An Approach to Designing and Implementing Virtual Museums}, booktitle = {Proceedings of the seventh UK VR-SIG Conference}, year = {2000}, month = {9}, abstract = {The current paper describes an approach to designing and implementing a virtual environment comprising ten different museums. The number of museums as well as the variety of their exhibits lead to the adoption of a generalised strategy that catered for all museum presentation needs and allowed for future expansion. Furthermore, the system architecture supports the delivery of multimedia content either over the Internet or via a local immersive virtual reality installation.}, author = {D. Charitos and Giorgos Lepouras and Costas Vassilakis and Akrivi Katifori and C. Halatsis} } @article {DBLP:journals/debu/VassiliadisVSK00, title = {ARKTOS: A Tool For Data Cleaning and Transformation in Data Warehouse Environments}, journal = {IEEE Data Eng. Bull.}, volume = {23}, number = {4}, year = {2000}, pages = {42{\textendash}47}, url = {http://sites.computer.org/debull/A00DEC-CD.pdf}, author = {Panos Vassiliadis and Zografoula Vagena and Spiros Skiadopoulos and Nikos Karayannidis} } @article {Kovacs2000417, title = {Function oriented history representation in databases}, journal = {Computers and Artificial Intelligence}, volume = {19}, number = {5}, year = {2000}, note = {cited By (since 1996) 0}, pages = {417-444}, abstract = {In the past years the management of temporal data has attracted numerous researchers resulting to a large number of temporal data extensions to the relational and object oriented data models. In this paper, the proposed temporal data model focuses on the functional characteristics of the histories. The paper introduces a set oriented description of the calendars together with a function oriented history concept with a history-algebra. The completeness of the proposed model with respect to the reduced temporal algebra TA is also proven. The expressive power of the proposed model is demonstrated in the end of the paper by a hospital example.}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-33751245138\&partnerID=40\&md5=575f314a008c5f0b9ae258689c3de7be}, author = {Kovacs, L. and Costas Vassilakis} } @article {DBLP:journals/ai/KoubarakisS00, title = {Querying temporal and spatial constraint networks in PTIME}, journal = {Artif. Intell.}, volume = {123}, number = {1-2}, year = {2000}, pages = {223{\textendash}263}, doi = {10.1016/S0004-3702(00)00055-2}, url = {https://doi.org/10.1016/S0004-3702(00)00055-2}, author = {Manolis Koubarakis and Spiros Skiadopoulos} } @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.} } @conference {DBLP:conf/aaai/KoubarakisS99, title = {Querying Temporal Constraint Networks in PTIME}, booktitle = {Proceedings of the Sixteenth National Conference on Artificial Intelligence and Eleventh Conference on Innovative Applications of Artificial Intelligence, July 18-22, 1999, Orlando, Florida, USA.}, year = {1999}, pages = {745{\textendash}750}, url = {http://www.aaai.org/Library/AAAI/1999/aaai99-106.php}, author = {Manolis Koubarakis and Spiros Skiadopoulos} } @conference {DBLP:conf/stdbm/KoubarakisS99, title = {Tractable Query Answering in Indefinite Constraint Databases: Basic Results and Applications to Querying Spatiotemporal Information}, booktitle = {Spatio-Temporal Database Management, International Workshop STDBM{\textquoteright}99, Edinburgh, Scotland, September 10-11, 1999, Proceedings}, year = {1999}, pages = {204{\textendash}223}, doi = {10.1007/3-540-48344-6_12}, url = {https://doi.org/10.1007/3-540-48344-6_12}, author = {Manolis Koubarakis and Spiros Skiadopoulos} } @conference {1993-kassapidis-hci, title = {Comparative Study of Protocols of the Transport Layer for Multimedia Applications}, booktitle = {Proceedings of the 4th Hellenic Conference on Informatics}, year = {1993}, month = {12}, pages = {105-118}, abstract = {The forthcoming use of multimedia applications will require powerful computers and high performance networks. While great progress has been made to the physical layer of networks, the upper software layers of the OSI reference model have not kept up pace with them. This paper presents the demands imposed by multimedia applications on the underlying networks and their mapping to transport layer services, that protocols implementing it must provide. Four well-known transport layer protocols are briefly presented (TCP, TP4, VMTP, HSTP/XTP). The mechanisms employed by each one of those are studied and their suitability for demanding multimedia environments are evaluated. We conclude that much more effort needs to be made on the transport layer protocols so that high performance network architectures will be available to fullfill the diverse requirements of tomorrow{\textquoteright}s multimedia applications.}, url = {http://cst.uop.gr/images/papers/1993-kassapidis-hci.pdf}, author = {Kassapidis, P. and Costas Vassilakis and M. Nikolaidou and P. Georgiadis and Votsis, Gr. and Pronios, N.} }