@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} } @conference {829, title = {Estimating \iSAX Parameters for Efficiency}, booktitle = {New Trends in Database and Information Systems (Proceedings of the 2023 European Conference on Advances in Databases and Information Systems / ADBIS 2023)}, year = {2023}, publisher = {Springer Nature Switzerland}, organization = {Springer Nature Switzerland}, address = {Cham}, abstract = {

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

}, keywords = {Indexing, Parameter tuning, SAX, Time series}, isbn = {978-3-031-42941-5}, doi = {10.1007/978-3-031-42941-5_1}, author = {Tsoukalos, Michalis and Platis, Nikos and Vassilakis, Costas} } @conference {825, title = {Estimating \iSAX Parameters for Efficiency}, booktitle = {Proceedings of the 27th European Conference on Advances in Databases and Information Systems (ADBIS 2023)}, year = {2023}, abstract = {

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

}, keywords = {Indexing, Parameter tuning, SAX, Time series}, author = {Tsoukalos, Michalis and Platis, Nikos and Vassilakis, Costas} } @article {814, title = {The additional testsuite framework: facilitating software testing and test management}, journal = {International Journal of Web Engineering and Technology}, volume = {TBD}, year = {2022}, abstract = {

In this paper, we present the Additional Testsuite Framework, a novel test suite management approach, which provides structures and instrumentation for the creation, maintenance, evolution and use of test suites for software programs. In particular, the tests can be maintained in a centralized repository, and are developed and maintained independently of specific versions of the associated software. Through the use of annotations, tests are categorized and distributed to the desired versions of the software. The presented framework also supports test-based development, dynamic/selective program builds, feature-based builds, testing in different environments and source code analysis. The Additional Testsuite Framework concept has been implemented and extensively evaluated, with the test cases notably including the JBoss EAP CE and OpenLiberty servers.

}, keywords = {Additional Testsuite Framework, Dynamic Testing, Feature-based testing, Internet application testing, Multiple Environment Testing, Multiversion Testing, Test program repository, Test-Driven Development, Testsuite Management}, author = {Sotiropoulos, Panagiotis and Vassilakis, Costas} } @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} } @conference {809, title = {Digital applications for the preservation of historic memory: the case of the Kalamata digital museum (greek title: Ψηφιακές εφαρμογές για τη διατήρηση της ιστορικής μνήμης: Η περίπτωση του ψηφιακού μουσείου Καλαμάτας)}, booktitle = {4th PanHellenic Conference on Digital Cultural Heritage-EuroMed 2021}, year = {2021}, abstract = {

The evolution in technology and informatics have changed all aspects of our lives, including civilization-related ones. And while interdisciplinary research involving the scientific disciplines of human sciences and informatics was underdeveloped for many years, it seems that informatics and technology can constitute the catalyst for the rapid advancement of certain areas in human sciences. This has become more than apparent during the last decade, especially in museums and venues related to civilization, where the application of technology, both for the improvement of the visitors{\textquoteright} experience and for the support of scientists (archaeologists, museologists etc), is now taken as granted. In particular, the measures that have been applied during the last two years of the COVID19 pandemic, further accelerate the developments towards digitalization and switching to an online world. The "Kalamata 1821: roads of freedom" project was the starting point for the creation of the first mixed digital museum in the region of the Peloponnese; this museum is strongly related to the history of Greece, starting from the Revolution of 1821 and its relationship with Kalamata. This paper analyses the process of design, preparation and implementation of digital multimedia applications that are installed on the digital museum infrastructure. The applications have been designed to maximize the information that can be perceived within the limited time frame during of a museum visit, offering in parallel means to obtain some of the information presented and store them on a mobile device.

}, author = {Poulopoulos, Vassileios and Wallace, Manolis and Antoniou, Antzela and Vassilakis, Costas and Panagiotidi, Vayia and Zacharias, Nikolaos} } @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 {801, title = {An Interface for User-Centred Process and Correlation Between Large Datasets}, booktitle = {Proceedings of the 2021 International Conference on Human-Computer Interaction: Design, User Experience, and Usability: UX Research and Design}, year = {2021}, publisher = {Springer International Publishing}, organization = {Springer International Publishing}, address = {Cham}, abstract = {

Standard database query systems are designed to process data on a single installation only, and do not provide optimal solutions for cases that data from multiple sources need to be queried. In these cases, the sources may have different data schemata, data representations etc., necessitating extensive coding and data transformations to retrieve partial results and combine them to reach the desired outcome. Differences in schemata and representations may be subtle and remain unnoticed, leading to the production of erroneous results. The goal of this paper is to present an easy-to-use solution for the end users, enabling them to query data from a given set of databases through a single user interface. This user interface allows users to visualize database contents and query results, while facilities for uploading and validating the data are also accommodated. To demonstrate the applicability of our approach, a use case is presented where data from two different sources are uploaded into the system and thereafter the data from the two databases can be utilized in tandem. The usability evaluation involved software developers in free evaluation scenarios.

}, keywords = {big data, Multiple data sources, Query, Usability, user interface, Visualisation}, isbn = {978-3-030-78221-4}, doi = {https://doi.org/10.1007/978-3-030-78221-4_32}, author = {Spiliotopoulos, Dimitris and Giannakopoulos, Theodoros and Vassilakis, Costas and Wallace, Manolis and Lantzouni, Marina and Poulopoulos, Vassilis and Margaris, Dionisis} } @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} } @conference {802, title = {A User Interface for Personalising WS-BPEL Scenarios}, booktitle = {Proceedings of the 2021 International Conference on Human-Computer Interaction: HCI in Business, Government and Organizations}, year = {2021}, publisher = {Springer International Publishing}, organization = {Springer International Publishing}, address = {Cham}, abstract = {

Due to the huge volume of web services available, both locally and in the cloud, the performance of users and systems need significant research attention. Since WS-BPEL is the dominant language for orchestrating individual web services into business processes, by composing WS-BPEL scripts/scenarios, graphical notations facilitating WS-BPEL design can be extremely useful. Current user interfaces allow WS-BPEL designers not only to invoke selected web services, but also to explicitly ask for recommendations. Then, the user interface appends the services achieving the highest score, according to the attributes{\textquoteright} importance, set by the designer, to their WS-BPEL scenario. However, since the final selection is produced automatically, rather than relying on the designers{\textquoteright} choices, many times, from a personalisation point of view, the adaptation fails. This work reports on the design, development and user evaluation of a user interface that incorporates functionalities that support the designers{\textquoteright} selection performance, thereby upgrading the personalisation level of the WS-BPEL scenarios, as well as the success of the adaptation.

}, keywords = {Personalisation, Recommender Systems, Usability, User evaluation, user interface, Web services, WS-BPEL scenarios}, isbn = {978-3-030-77750-0}, doi = {https://doi.org/10.1007/978-3-030-77750-0_25}, author = {Margaris, Dionisis and Spiliotopoulos, Dimitris and Vasilopoulos, Dionysios and Vassilakis, Costas} } @article {749, title = {Human behaviour in multimodal interaction: main effects of civic action and interpersonal and problem-solving skills}, journal = {Journal of Ambient Intelligence and Humanized Computing}, volume = {TBD}, year = {2020}, month = {mar}, pages = {TBD}, abstract = {Metacognitive skill training may rest within any kind of social interaction that requires awareness of what an individual and others think, in social, educational and organizational settings alike. This work explores an extensive study of multimodal application interaction (virtual agent, spoken dialogue, visual communication of progress) for metacognitive skill training via negotiation skill training settings. Human behaviour, as effected by civic action and interpersonal and problem-solving skill training, is investigated through interaction sessions with a virtual agent on multimodal multiparty negotiation. This work reports on the results of the user-system evaluation sessions involving 41 participants before-and-after interaction with the system, integrating macro- (dialogue system performance) and micro- (metacognitive-related and individual-and-community level-related attitudes and skills) factors. Findings indicate significant and positive relationships between user and system evaluation questions after interaction with the dialogue system and between self-efficacy, self-regulation, individual readiness to change, mastery goal orientation, interpersonal and problem-solving skills and civic action before-and-after the interaction experience. Implications, limitations and further research issues are discussed in light of context of the multimodal interaction and its effects on the human behaviour during metacognitive skill training.}, keywords = {Human Behaviour, Individual- and Community-Level Related Attitudes and Skills, Metacognitive, Multimodal Interaction, Skill Training}, doi = {10.1007/s12652-020-01846-x}, author = {Markri, Eleni and Spiliotopoulos, Dimitris and Vassilakis, Costas and Margaris, Dionisis} } @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 {722, title = {Handling uncertainty in social media textual information for improving venue recommendation formulation quality in social networks}, journal = {Social Network Analysis and Mining}, volume = {9}, year = {2019}, month = {Oct}, pages = {64}, abstract = {One of the major problems that social media front is to continuously produce successful, user-targeted information, in the form of recommendations, which are produced by applying methods from the area of recommender systems. One of the most important applications of recommender systems in social networks is venue recommendation, targeted by the majority of the leading social networks (Facebook, TripAdvisor, OpenTable, etc.). However, recommender systems{\textquoteright} algorithms rely only on the existence of numeric ratings which are typically entered by users, and in the context of social networks, this information is scarce, since many social networks allow only reviews, rather than explicit ratings. Even if explicit ratings are supported, users may still resort to expressing their views and rating their experiences through submitting posts, which is the predominant user practice in social networks, rather than entering explicit ratings. User posts contain textual information, which can be exploited to compute derived ratings, and these derived ratings can be used in the recommendation process in the lack of explicitly entered ratings. Emerging recommender systems encompass this approach, without however tackling the fact that the ratings computed on the basis of textual information may be inaccurate, due to the very nature of the computation process. In this paper, we present an approach which extracts features of the textual information, a widely available source of information in venue category, to compute a confidence metric for the ratings that are computed from texts; then, this confidence metric is used in the user similarity computation and venue rating prediction formulation process, along with the computed rating. Furthermore, we propose a venue recommendation method that considers the generated venue rating predictions, along with venue QoS, similarity and spatial distance metrics in order to generate venue recommendations for social network users. Finally, we validate the accuracy of the rating prediction method and the user satisfaction from the recommendations generated by the recommendation formulation algorithm. Conclusively, the introduction of the confidence level significantly improves rating prediction accuracy, leverages the ability to generate personalized recommendations for users and increases user satisfaction.}, keywords = {collaborative filtering, Confidence level, Rating prediction, Recommender Systems, Social Networks, Textual information, Uncertainty, Venue recommendation formulation}, issn = {1869-5469}, doi = {10.1007/s13278-019-0610-x}, url = {https://doi.org/10.1007/s13278-019-0610-x}, author = {Margaris, Dionisis and Vassilakis, Costas and Spiliotopoulos, Dimitris} }