@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}
}
@article {589,
	title = {Efficient Continuous Multi-Query Processing over Graph Streams},
	journal = {CoRR},
	volume = {abs/1902.05134},
	year = {2019},
	url = {http://arxiv.org/abs/1902.05134},
	author = {Lefteris Zervakis and Vinay Setty and Christos Tryfonopoulos and Katja Hose}
}
@proceedings {DBLP:conf/pakdd/2018-2,
	title = {Advances in Knowledge Discovery and Data Mining - 22nd Pacific-Asia Conference, PAKDD 2018, Melbourne, VIC, Australia, June 3-6, 2018, Proceedings, Part II},
	volume = {10938},
	year = {2018},
	publisher = {Springer},
	isbn = {978-3-319-93036-7},
	doi = {10.1007/978-3-319-93037-4},
	url = {https://doi.org/10.1007/978-3-319-93037-4},
	editor = {Dinh Q. Phung and Vincent S. Tseng and Geoffrey I. Webb and Bao Ho and Mohadeseh Ganji and Lida Rashidi}
}
@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}
}
@inbook {marg16d,
	title = {Knowledge-Based Leisure Time Recommendations in Social Networks},
	booktitle = {Current Trends on Knowledge-Based Systems},
	series = {Intelligent Systems Reference Library},
	year = {2017},
	pages = {23{\textendash}48},
	publisher = {Springer International Publishing},
	organization = {Springer International Publishing},
	chapter = {Knowledge-Based Leisure Time Recommendations in Social Networks},
	abstract = {We introduce a novel knowledge-based recommendation algorithm for leisure time information to be used in social networks, which enhances the state-of-the-art in this algorithm category by taking into account (a) qualitative aspects of the recommended places (restaurants, museums, tourist attractions etc.), such as price, service and atmosphere, (b) influencing factors between social network users, (c) the semantic and geographical distance between locations and (d) the semantic categorization of the places to be recommended. The combination of these features leads to more accurate and better user-targeted leisure time recommendations.},
	keywords = {Attribute constraints, collaborative filtering, Knowledge-based Recommender Systems, Semantic Information, Social Networks},
	doi = {10.1007/978-3-319-51905-0_2},
	author = {Dionisis Margaris and Costas Vassilakis and P. Georgiadis},
	editor = {Giner Alor Hernandez and Rafael Valencia Garcia}
}
@proceedings {DBLP:conf/gis/2017,
	title = {Proceedings of the 25th ACM SIGSPATIAL International Conference on Advances in Geographic Information Systems, GIS 2017, Redondo Beach, CA, USA, November 7-10, 2017},
	year = {2017},
	publisher = {ACM},
	isbn = {978-1-4503-5490-5},
	url = {http://dl.acm.org/citation.cfm?id=3139958},
	editor = {Erik G. Hoel and Shawn D. Newsam and Siva Ravada and Roberto Tamassia and Goce Trajcevski}
}
@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}
}
@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}
}
@conference {537,
	title = {Anonymity and Censorship Resistance in Unstructured Overlay Networks},
	booktitle = {Proceedings of the 17th International Conference on Cooperative Information Systems (CoopIS)},
	year = {2009},
	month = {November},
	address = {Vilamoura, Portugal},
	author = {Michael Backes and Marek Hamerlik and Alessandro Linari and Matteo Maffei and Christos Tryfonopoulos and Gerhard Weikum}
}
@conference {torou2009a,
	title = {Capturing the historical research methodology: an experimental approach},
	booktitle = {Proceedings of International Conference of Education, Research and Innovation (ICERI 2009)},
	year = {2009},
	month = {11},
	abstract = {This paper presents the results of a study on how historians conduct research in a historical archive, and the methodologies they use while searching. Historic research involves finding, using, interpreting and correlating information within primary and secondary sources, in order to understand past events. The collection of historical data is accomplished through methodical and comprehensive research in primary and secondary sources. An important factor in our study was to understand what kind of data and/or information historians are looking for in a library/historical archive, either printed or digitized, and which research methodologies or research models they use while they investigate a historical archive. Since this issue has not been addressed insofar, and therefore there are no methods for elucidating research methodologies or research models that historians employ / use, we formulated a questionnaire comprising of seven information retrieval tasks commonly addressed in the context of historic research. History researchers were asked to describe in detail how they would proceed in searching for the information they need for completing these tasks. Through this procedure we aimed to investigate the different ways a historian can use to tackle a specific question, examine whether there exists a common research methodology, and the historic researchers? expectations and preferences. The insight gained from this investigation can be used for educational purposes, since it could be useful in the creation / development of a methodology for conducting research on historical information. Furthermore, the findings can be exploited in the context of organizing documents within historical source repositories, so as to facilitate the retrieval of documents by historians; finally the presented findings can serve as a preliminary requirement analysis phase for building tools that will enable historians to access more rapidly and fully the information they need.},
	author = {Elena Torou and Akrivi Katifori and Costas Vassilakis and Giorgos Lepouras and C. Halatsis}
}
@conference {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}
}
@booklet {569,
	title = {Anonymous and Censorship-resistant Content-sharing in Unstructured Overlays},
	year = {2008},
	author = {Michael Backes and Marek Hamerlik and Alessandro Linari and Matteo Maffei and Christos Tryfonopoulos and Gerhard Weikum}
}
@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 {566,
	title = {P2P Information Retrieval and Filtering with MAPS},
	booktitle = {Proccedings of the IEEE International Conference on Peer-to-Peer Computing (P2P)},
	year = {2008},
	month = {September},
	address = {Aachen, Germany},
	author = {Christian Zimmer and Johannes Heinz and Christos Tryfonopoulos and Gerhard Weikum}
}
@conference {Katifori2008133,
	title = {Selected results of a comparative study of four ontology visualization methods for information retrieval tasks},
	booktitle = {Proceedings of the 2nd International Conference on Research Challenges in Information Science, RCIS 2008},
	year = {2008},
	note = {cited By (since 1996) 0},
	month = {6},
	pages = {133-140},
	abstract = {The need for effective ontology visualization for design, management and browsing has arisen as a result of the progress in the areas of Semantic Web and Personal Information Management. There are several ontology visualizations available through existing ontology management tools, but not as many evaluations to determine their advantages and disadvantages and their suitability for various ontologies and user groups. This work presents selected results of an evaluation of four visualization methods in ProtΓ{\textcopyright}gΓ{\textcopyright}.},
	keywords = {Communication, Comparative studies, Information management, Information retrieval, Information science, Information services, Information theory, Management, Management information systems, Ontology, Ontology managements, Personal Information managements, Semantic Web, Telecommunication services, User groups, User interfaces, Visualization, visualization methods},
	doi = {10.1109/RCIS.2008.4632101},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-57349172797\&partnerID=40\&md5=1f36a9a0febecb929cd7904c84004143},
	author = {Akrivi Katifori and Elena Torou and Costas Vassilakis and Giorgos Lepouras and C. Halatsis}
}
@conference {Katifori200832,
	title = {Supporting research in historical archives: Historical information visualization and modeling requirements},
	booktitle = {Proceedings of the International Conference on Information Visualisation},
	year = {2008},
	note = {cited By (since 1996) 0},
	month = {7},
	pages = {32-37},
	abstract = {The on-going progress in the area of digital libraries has lead to the beginning of a digitization effort in Historical Archives, as well. The requirements of historical research, which works with histories of entities and incomplete information, create the need for supplementary tools to support users in handling the digitized content. This work is based on a user study of historian information retrieval methods in order to create a set of tools for the context of historical archives, which will facilitate historical data storage, management and visualization. Β{\textcopyright} 2008 IEEE.},
	keywords = {Data visualization, Digital libraries, Heuristics, Historical archive, Information analysis, Information management, Information retrieval, Information science, Information services, Information systems, International conferences, Libraries, Ontology, Search engines, Visualization},
	doi = {10.1109/IV.2008.70},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-51749114860\&partnerID=40\&md5=a5b3e7f74314d5651816424c11e6cbc1},
	author = {Akrivi Katifori and Elena Torou and Costas Vassilakis and C. Halatsis}
}
@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}
}
@article {Lepouras200779,
	title = {Domain expert user development: The smartgov approach},
	journal = {Communications of the ACM},
	volume = {50},
	number = {9},
	year = {2007},
	month = {sep},
	pages = {79-83},
	publisher = {Association for Computing Machinery (ACM)},
	abstract = {SmartGov project funded by the European Union is a knowledge-based platform that assists pubic-sector employees with suitable expertise to generate online transaction devices by simplifying service development, maintenance, and integration with installed information technology systems. The project delivers intelligent e-forms development and maintenance environment and associated framework for e-government services. SmartGov address various problems faced by the stakeholders while implementing e-services such as limited view of domain experts, lost information, complexity of creating e-forms, and inadequate access. In a SmartGov approach, the implicit knowledge is made explicit in the form of documentation and data validation rules. The central concept of SmartGov is the transaction service element (TSE) that contain metadata and domain knowledge.},
	keywords = {Data validation, Documentation, Information services, Information technology, Knowledge based platform, Knowledge based systems, Metadata, Online systems, Project management, Transaction service element (TSE)},
	doi = {10.1145/1284621.1284623},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-34548411694\&partnerID=40\&md5=43df285b5a79ef731b3466106642af9f},
	author = {Giorgos Lepouras and Costas Vassilakis and C. Halatsis and P. Georgiadis}
}
@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}
}
@article {Vassilakis2007113,
	title = {A knowledge-based approach for developing multi-channel e-government services},
	journal = {Electronic Commerce Research and Applications},
	volume = {6},
	number = {1},
	year = {2007},
	note = {cited By (since 1996) 0},
	pages = {113-124},
	abstract = {Having realised the benefits resulting from delivering on-line public services in the context of electronic government, administrations strive to extend the spectrum of services offered to citizens and enterprises, as well as to engage multiple communication channels in service delivery, in order to increase the target audience and, consequently, the service effectiveness. Insofar, however, only the web channel has been sufficiently used for service delivery, whereas other channels have not been adequately exploited. One of the main reasons of this lag is the cost incurred for the development and maintenance of multiple versions of an electronic service, each version targeted to a different platform. In this paper, we present an approach and the associated tools for developing and maintaining electronic services that allows the automated production of different versions of the electronic service, each targeted to a specific platform. Β{\textcopyright} 2006 Elsevier B.V. All rights reserved.},
	keywords = {Communication channels (information theory), e-government, Electronic commerce, electronic services, EServices, Government data processing, Knowledge based systems, Multi channel service delivery, Online systems, Websites},
	doi = {10.1016/j.elerap.2006.07.004},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-33947371200\&partnerID=40\&md5=ebf06c2eee159fbeeab64c607e84415d},
	author = {Costas Vassilakis and Giorgos Lepouras and C. Halatsis}
}
@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 {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 {597,
	title = {Design and Evaluation of Semantic Similarity Measures for Concepts Stemming from the Same or Different Ontologies},
	booktitle = {Proceedings of the 4th Workshop on Multimedia Semantics (WMS)},
	year = {2006},
	month = {June},
	address = {Chania, Crete, Greece},
	abstract = {Semantic Similarity relates to computing the similarity between concepts (terms) which are not necessarily lexically similar. We investigate approaches to computing semantic similarity by mapping terms to an ontology and by examining their relationships in that ontology. More specifically, we investigate approaches to computing the semantic similarity between natural language terms (using WordNet as the underlying reference ontology) and between medical terms (using the MeSH ontology of medical and biomedical terms). The most popular semantic similarity methods are implemented and evaluated using WordNet and MeSH. The focus of this work is also on cross ontology methods which are capable of computing the semantic similarity between terms stemming from different ontologies (WordNet and MeSH in this work). This is a far more difficult problem (than the single ontology one referred to above) which has not been investigated adequately in the literature. X-Similarity, a novel cross-ontology similarity method is also a contribution of this work. All methods examined in this work are integrated into a semantic similarity system which is accessible on the Web.},
	author = {E.G.M. Petrakis and Giannis Varelas and Angelos Hliaoutakis and Paraskevi Raftopoulou}
}
@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}
}
@article {592,
	title = {X-Similarity: Computing Semantic Similarity between Concepts from Different Ontologies},
	journal = {Journal of Digital Information Management (JDIM)},
	year = {2006},
	month = {December},
	abstract = {Semantic Similarity relates to computing the similarity between concepts (terms) which are not necessarily lexically similar. We investigate approaches to computing semantic similarity by mapping terms to an ontology and by examining their relationships in that ontology. More specifically, we investigate approaches to computing the semantic similarity between natural language terms (using WordNet as the underlying reference ontology) and between medical terms (using the MeSH ontology of medical and biomedical terms). The most popular semantic similarity methods are implemented and evaluated using WordNet and MeSH. The focus of this work is also on cross ontology methods which are capable of computing the semantic similarity between terms stemming from different ontologies (WordNet and MeSH in this work). This is a far more difficult problem (than the single ontology one referred to above) which has not been investigated adequately in the literature. X-Similarity, a novel cross-ontology similarity method is also a contribution of this work. All methods examined in this work are integrated into a semantic similarity system which is accessible on the Web.},
	author = {E.G.M. Petrakis and Giannis Varelas and Angelos Hliaoutakis and Paraskevi Raftopoulou}
}
@article {Vassilakis_barriersto,
	title = {Barriers To Electronic Service Development},
	journal = {e-Service Journal},
	volume = {Fall 2005},
	year = {2005},
	pages = {41-63},
	abstract = {E-government initiatives have been proven to deliver significant benefits, both for suppliers of electronic services (public authorities and organizations) and for the public, to whom services are addressed. However, the pace with which electronic services are made available and adopted is lower than planned or expected; governments tend to be slow in releasing new services, and citizens often prefer to conduct business with the government through paper forms and physical presence, rather than using online methods. This indicates that certain barriers exist that hinder the transition to electronic services. In this paper, we present the results of a survey among electronic service stakeholder groups, to identify the most important barriers to electronic service development. Documentation of barriers is considered important, since administrations may take certain measures to overcome them. Hints on how specific barriers may be overcome are also provided.},
	doi = {10.2979/esj.2005.4.1.41},
	author = {Costas Vassilakis and Giorgos Lepouras and John Fraser and Simon Haston}
}
@article {DBLP:journals/eg/VassilakisLHL05,
	title = {An XML model for electronic services},
	journal = {Electronic Government},
	volume = {2},
	number = {1},
	year = {2005},
	pages = {41-55},
	abstract = {With the need for electronic services to be developed and deployed more and more rapidly, it is imperative that concrete models of electronic services are developed, to facilitate systematic work of electronic service stakeholders, concrete semantics and coherent representations across services developed within an organisation. Using the XML language to develop such a model, offers a number of additional advantages, such as rich semantics, facilitation of data interchange, extensibility, high abstraction levels and possibility for mechanical processing. In this paper we present the design aspects of an XML model for electronic services, which has been used for building a repository of interlinked elements representing e-services. A web-based interface for the management of this repository and a tool for automatically compiling e-service descriptions into executable images have been developed alongside. The model has been evaluated by a mixture of electronic service stakeholders, and the results of this evaluation are also presented.},
	doi = {10.1504/EG.2005.006647},
	author = {Costas Vassilakis and Giorgos Lepouras and C. Halatsis and Tomas Pariente Lobo}
}
@conference {Weir2004152,
	title = {Content enrichment through dynamic annotation},
	booktitle = {ICEIS 2004 - Proceedings of the Sixth International Conference on Enterprise Information Systems},
	year = {2004},
	note = {cited By (since 1996) 0},
	month = {4},
	pages = {152-157},
	abstract = {This paper describes a technique for interceding between users and the information that they browse. This facility, that we term {\textquoteright}dynamic annotation{\textquoteright}, affords a means of editing Web page content {\textquoteright}on-the-fly{\textquoteright} between the source Web server and the requesting client. Thereby, we have a generic way of modifying the content displayed to local users by addition, removal or reorganising any information sourced from the World-Wide Web, whether this derives from local or remote pages. For some time, we have been exploring the scope for this device and we believe that it affords many potential worthwhile applications. Here, we describe two varieties of use. The first variety focuses on support for individual users in two contexts (second-language support and second language learning). The second variety of use focuses on support for groups of users. These differing applications have a common goal which is content enrichment of the materials placed before the user. Dynamic annotation provides a potent and flexible means to this end.},
	keywords = {Content based retrieval, Content enrichment, Dynamic annotation, Information analysis, Knowledge based systems, Learning systems, Servers, Web browsers, World Wide Web},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-8444234304\&partnerID=40\&md5=1ba0d141296de4e5b8bbd76ba0d1d79a},
	author = {G.R.S. Weir and Giorgos Lepouras and Costas Vassilakis},
	editor = {I. Seruca and J. Filipe and S. Hammoudi and J. Cordeiro}
}
@conference {lep2002a1,
	title = {SMARTGOV: A Governmental Knowledge-based Platform for Public Sector Online Services},
	booktitle = {Proceedings KMGov2002},
	year = {2002},
	month = {5},
	pages = {173{\textendash}185},
	address = {Copenhagen, Denmark},
	abstract = {Public transaction services (such as e-forms), although perceived the future of e-government have not yet realised their full potential. E-forms have a significant role in e-government, as they are the basis for realising most of the twenty public services that all European Union member states have to provide to their citizens and businesses. The aim of this paper is to present a knowledge-based platform to assist public sector employees to generate online transaction services by simplifying their development, maintenance and integration with already installed IT systems.},
	author = {E. Tambouris and G. Boukis and Costas Vassilakis and Giorgos Lepouras and S. Rouvas and Canadas, R. and Heredia, S. and Lopez Usero, J. C.}
}
@conference {599,
	title = {Agents in Decentralised Information Ecosystems: The DIET Approach},
	booktitle = {Symposium on Information Agents for E-Commerce, AISB Convention},
	year = {2001},
	month = {March},
	address = {University of York, United Kingdom},
	abstract = {The complexity of the current global information infrastructure requires novel means of understanding and exploiting the dynamics of information. One means may be through the concept of an information ecosystem. An information ecosystem is analogous to a natural ecosystem in which there are flows of materials and energy analogous to information flow between many interacting individuals. This paper describes a multi-agent platform, DIET (Decentralised Information Ecosystem Technologies) that can be used to implement open, robust, adaptive and scalable ecosystem-inspired systems. We describe the design principles of the DIET software architecture, and present a simple example application based upon it. We go on to consider how the DIET system can be used to develop information brokering agents, and how these can contribute to the implementation of economic interactions between agents, as well as identifying some open questions relating to research in these areas. In this way we show the capacity of the DIET system to support applications using information agents.},
	author = {P. Marrow and Manolis Koubarakis and R.H. van Lengen and F. Valverde-Albacete and E. Bonsma and J. Cid-Suerio and A.R. Figueiras-Vidal and A. Gallardo-Antolin and C. Hoile and T. Koutris and H. Molina-Bulla and A. Navia-Vazquez and Paraskevi Raftopoulou and N. Skarmeas and Christos Tryfonopoulos and F. Wang and C. Xiruhaki}
}
@conference {aisb01-MKL+,
	title = {Agents in Decentralised Information Ecosystems: The DIET Approach},
	booktitle = {Proccedings of the Symposium on Information Agents for E-Commerce, AISB Convention},
	year = {2001},
	month = {March},
	pages = {109{\textendash}117},
	address = {York, UK},
	author = {P. Marrow and Manolis Koubarakis and R.H. van Lengen and F. Valverde-Albacete and E. Bonsma and J. Cid-Suerio and A.R. Figueiras-Vidal and A. Gallardo-Antolin and C. Hoile and T. Koutris and H. Molina-Bulla and A. Navia-Vazquez and Paraskevi Raftopoulou and N. Skarmeas and Christos Tryfonopoulos and F. Wang and C. Xiruhaki}
}
@conference {Lep01a,
	title = {Building a VR - Museum in a Museum},
	booktitle = {Proceedings of the Third International Virtual Reality Conference, VRIC2001},
	year = {2001},
	month = {5},
	abstract = {Past years have seen the exploitation of multimedia techniques and lately the introduction of virtual reality methods to create new forms of presentation for museums{\textquoteright} exhibitions. Virtual Reality can offer a number of advantages to museums, offering a way to overcome some common problems like the lack of space or the need of visitors to interact with the exhibits. A broad categorisation of virtual museums reveals that they vary from fully immersive cave systems to simple multimedia presentations. In our approach to develop a virtual reality museum we have designed a virtual environment (VE) where guests can visit a total of ten different museums. The processes of digitisation, architectural design and exhibit presentation are outlined and points of particular importance are explained. Exhibits from the real world museums have been digitised and integrated in the VE. The system has been implemented in two versions: one fully immersive and one with a stereo display.},
	author = {Giorgos Lepouras and D. Charitos and Costas Vassilakis and Charissi, A. and Halatsi, L.}
}
@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}
}
@proceedings {DBLP:conf/aaai/1999,
	title = {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},
	publisher = {AAAI Press / The MIT Press},
	isbn = {0-262-51106-1},
	url = {http://www.aaai.org/Conferences/AAAI/aaai99.php},
	editor = {Jim Hendler and Devika Subramanian}
}
@article {Spiliopoulou1996341,
	title = {A cost model for the estimation of query execution time in a parallel environment supporting pipeline},
	journal = {Computers and Artificial Intelligence},
	volume = {15},
	number = {4},
	year = {1996},
	note = {cited By (since 1996) 3},
	pages = {341-368},
	abstract = {We propose a model for the estimation of query execution time in an environment supporting bushy and pipelined parallelism. We consider a parallel architecture of processors having private main memories, accessing a shared secondary storage and communicating to each other via a network. For this environment, we compute the cost of query operators when processed in isolation and when in pipeline mode. We use those formulae to incrementally compute the cost of a query execution plan from its components. Our cost model can be incorporated to any optimizer for parallel query processing that considers parallel and pipelined execution of the query operators.},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-33747804589\&partnerID=40\&md5=e04ec1604249525ebaf3dfb111a34f12},
	author = {M. Spiliopoulou and M. Hatzopoulos and Costas Vassilakis}
}
@article {1993-spiliopoulou-cai,
	title = {Parallel Optimisation of Join Queries Using a Technique of Exhaustive Nature},
	journal = {Computers and Artificial Intelligence},
	volume = {12},
	number = {2},
	year = {1993},
	pages = {145{\textendash}166},
	abstract = {In this study we present a technique for the parallel optimisation of join queries that uses the offered coarse-grain parallelism of the underlying architecture in order to reduce the CPU-bound optimisation overhead. The optimisation technique performs an almost exhaustive search of the solution space for small join queries and gradually, as the number of joins increases, it diverges towards iterative improvement. This technique has been developed on a low-parallelism transputer-based architecture, where its behaviour is studied for the optimisation of queries with many tens of joins.},
	keywords = {databases},
	author = {M. Spiliopoulou and M. Hatzopoulos and Costas Vassilakis}
}
@conference {1992-spiliopoulou-parle,
	title = {Using Parallelism and Pipeline for the Optimisation of Join Queries},
	booktitle = {PARLE {\textquoteright}92: Proceedings of the 4th International PARLE Conference on Parallel Architectures and Languages Europe},
	year = {1992},
	month = {6},
	pages = {279{\textendash}294},
	publisher = {Springer-Verlag},
	organization = {Springer-Verlag},
	address = {London, UK},
	abstract = {In this study we present a technique for the parallel optimisation of join queries, that uses the offered coarse-grain parallelism of the underlying architecture in order to reduce the CPU-bound optimisation overhead. The optimisation technique performs an almost exhaustive search of the solution space for small join queries and gradually, as the number of joins increases, it diverges towards iterative improvement. This technique has been developed on a low-parallelism transputer-based architecture, where its behaviour is studied for the optimisation of queries with many tenths of joins.},
	isbn = {3-540-55599-4},
	doi = {10.1007/3-540-55599-4_94},
	author = {M. Spiliopoulou and M. Hatzopoulos and Costas Vassilakis}
}
@conference {1990-hatzopoulos-delta,
	title = {An Object-Oriented Data Model for Hypermedia Systems},
	booktitle = {Proceedings of the DELTA Conference in Research and Development},
	year = {1990},
	month = {10},
	pages = {483{\textendash}493},
	abstract = {Hypermedia [1] is a fast growing field of research interest because of the new aspects introduced as far as it concerns the interaction between the machine and the user. The innovative features mainly refer to - the presence of various information types (multimedia environment) - the mapping of the semantic connections between information items into a flexible, efficient representation. This feature enables navigation through the information network in a meaningful way. Our effort concentrated on the definition and partial implementation of a flexible, general-purpose model through which the full capabilities of object-oriented programming can be exploited.},
	keywords = {databases},
	url = {http://cst.uop.gr/images/papers/1990-hatzopoulos-delta.pdf},
	author = {M. Hatzopoulos and D. Gouscos and M. Spiliopoulou and Costas Vassilakis and M. Vazirgiannis}
}
