@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}
}
@article {marg2017a-fgcs,
	title = {Query personalization using social network information and collaborative filtering techniques},
	journal = {Future Generation of Computer Systems},
	volume = {Special Issue on Recommender Systems for Large-Scale Social Networks},
	year = {2017},
	month = {jan},
	pages = {440{\textendash}450},
	abstract = {Query personalization has emerged as a means to handle the issue of information volume growth, aiming to tailor query answer results to match the goals and interests of each user. Query personalization dynamically enhances queries, based on information regarding user preferences or other contextual information; typically enhancements relate to incorporation of conditions that filter out results that are deemed of low value to the user and/or ordering results so that data of high value are presented first. In the domain of personalization, social network information can prove valuable; users{\textquoteright} social networks profiles, including their interests, influence from social friends, etc. can be exploited to personalize queries. In this paper, we present a query personalization algorithm, which employs collaborative filtering techniques and takes into account influence factors between social network users, leading to personalized results that are better-targeted to the user.},
	doi = {10.1016/j.future.2017.03.015},
	url = {http://www.sciencedirect.com/science/article/pii/S0167739X17303692},
	author = {Dionisis Margaris and Costas Vassilakis and P. Georgiadis}
}
@conference {margaris2016a,
	title = {Improving QoS Delivered by WS-BPEL Scenario Adaptation through Service Execution Parallelization},
	booktitle = {Proceedings of the 31st Annual ACM Symposium on Applied Computing},
	year = {2016},
	pages = {1590-1596},
	publisher = {ACM},
	organization = {ACM},
	abstract = {WS-BPEL scenario execution adaptation has been proposed by researchers as a response to the need of users to tailor the WS-BPEL scenario execution to their individual preferences; these preferences are typically expressed through Quality of Service (QoS) policies, which the adaptation mechanism considers in order to select the services that will ultimately be invoked to realize the desired business process. In this paper, we study the potential to parallelize the execution of the WS-BPEL scenario in order to minimize its response time and/or achieving higher scores in the other qualitative dimensions, such as cost, reliability, etc., at the same time. We also describe, develop and validate a parallelization algorithm for realizing the proposed enhancements.},
	doi = {10.1145/2851613.2851805},
	url = {https://dl.acm.org/citation.cfm?id=2851805},
	author = {Dionisis Margaris and Costas Vassilakis and P. Georgiadis}
}
@article {Margaris_2016,
	title = {Recommendation information diffusion in social networks considering user influence and semantics},
	journal = {Social Network Analysis and Mining},
	volume = {6},
	number = {1},
	year = {2016},
	month = {nov},
	pages = {108},
	publisher = {Springer Nature},
	abstract = {One of the major problems in the domain of social networks is the handling and diffusion of the vast, dynamic and disparate information created by its users. In this context, the information contributed by users can be exploited to generate recommendations for other users. Relevant recommender systems take into account static data from users{\textquoteright} profiles, such as location, age or gender, complemented with dynamic aspects stemming from the user behavior and/or social network state such as user preferences, items{\textquoteright} general acceptance and influence from social friends. In this paper, we enhance recommendation algorithms used in social networks by taking into account qualitative aspects of the recommended items, such as price and reliability, the influencing factors between social network users, the social network user behavior regarding their purchases in different item categories and the semantic categorization of the products to be recommended. The inclusion of these aspects leads to more accurate recommendations and diffusion of better user-targeted information. This allows for better exploitation of the limited recommendation space, and therefore online advertisement efficiency is raised.},
	keywords = {Collaborative filtering, Information diffusion, Quality of service, Semantic Information, Social Networks},
	doi = {10.1007/s13278-016-0416-z},
	url = {http://rdcu.be/mZ7e},
	author = {Dionisis Margaris and Costas Vassilakis and P. Georgiadis}
}
@conference {marg15a,
	title = {A Collaborative Filtering Algorithm with Clustering for Personalized Web Service Selection in Business Processes},
	booktitle = {Proceedings of RCIS 2015},
	year = {2015},
	month = {5},
	abstract = {Recommender systems aim to propose items that are expected to be of interest to the users. As one of the most successful approaches to building recommender systems, collaborative filtering exploits the known preferences of a group of users to formulate recommendations or predictions of the unknown preferences for other users. In many cases, collaborative filtering algorithms handle complex items, which are described using hierarchical tree structures containing rich semantic information. In order to make accurate recommendations on such items, the related algorithms must examine all aspects of the available semantic information. Thus, when collaborative filtering techniques are employed to adapt the execution of business processes, they must take into account the services{\textquoteright} Quality of Service parameters, so as to generate recommendations tailored to the individual user needs. In this paper, we present a collaborative filtering-based algorithm which takes into account the web services{\textquoteright} QoS parameters in order to tailor the execution of business processes to the preferences of users. An offline clustering technique is also introduced for supporting the efficient and scalable execution of proposed algorithm under the presence of large repositories of sparse data.},
	keywords = {business processes, clustering, collaborative filtering, hierarchical tree, performance, Quality of service, Web services},
	doi = {10.1109/RCIS.2015.7128877},
	author = {Dionisis Margaris and P. Georgiadis and Costas Vassilakis}
}
@conference {margaris2015a,
	title = {A Hybrid Framework for WS-BPEL Scenario Execution Adaptation, Using Monitoring and Feedback Data},
	booktitle = {Proceedings of the 30th ACM/SIGAPP Symposium On Applied Computing, SOAP track},
	year = {2015},
	month = {4},
	publisher = {ACM},
	organization = {ACM},
	abstract = {In this paper, we present a framework which provides runtime adaptation for BPEL scenarios. The adaptation is based on (a) quality of service parameters of available web services (b) quality of service policies specified by users (c) collaborative filtering techniques, allowing clients to further refine the adaptation process by considering service selections made by other clients, (d) monitoring, in order to follow the variations of QoS attribute values and (e) on users{\textquoteright} opinions services they have used.},
	doi = {10.1145/2695664.2695687},
	url = {https://dl.acm.org/citation.cfm?doid=2695664.2695687},
	author = {Dionisis Margaris and Costas Vassilakis and P. Georgiadis}
}
@article {margaris14a,
	title = {An integrated framework for adapting WS-BPEL scenario execution using QoS and collaborative filtering techniques},
	journal = {Science of Computer Programming},
	volume = {98},
	year = {2015},
	pages = {707{\textendash}734},
	abstract = {In this paper, we present a framework which incorporates runtime adaptation for BPEL scenarios. The adaptation is based on (a) the quality of service parameters of available services, allowing for tailoring their execution to the diverse needs of individual users and (b)collaborative filtering techniques, allowing clients to further refine the adaptation process by considering service selections made by other clients, in the context of the same business processes. The proposed framework also caters maintaining the transactional semantics that invocations to multiple services offered by the same provider may bear.},
	doi = {10.1016/j.scico.2014.10.007},
	url = {http://www.sciencedirect.com/science/article/pii/S0167642314004778},
	author = {Dionisis Margaris and Costas Vassilakis and P. Georgiadis}
}
@conference {margaris15c,
	title = {On Replacement Service Selection in WS-BPEL Scenario Adaptation},
	booktitle = {Proceedings of the 8th IEEE International Conference on Service Oriented Computing \& Applications (SOCA 2015)},
	year = {2015},
	month = {9},
	publisher = {IEEE},
	organization = {IEEE},
	abstract = {WS-BPEL scenario execution adaptation has been proposed by numerous researchers as a response to the need of users to tailor the WS-BPEL scenario execution to their individual preferences; these preferences are typically expressed through Quality of Service (QoS) policies, which the adaptation mechanism considers in order to select the services that will ultimately be invoked to realize the desired business process. In this paper, we consider a number of issues related to WS-BPEL scenario adaptation, aiming to enhance adaptation quality and improve the QoS offered to end users. More specifically, with the goal of broadening the service selection pool we (a) discuss the identification of potential services that can be used to realize a functionality used in the WS-BPEL scenario and (b) elaborate on transactional semantics that invocations to multiple services offered by the same provider may bear. We also describe and validate an architecture for realizing the proposed enhancements.},
	doi = {10.1109/SOCA.2015.11},
	author = {Dionisis Margaris and P. Georgiadis and Costas Vassilakis}
}
@conference {Margaris2013RCIS,
	title = {Adapting WS-BPEL scenario execution using collaborative filtering techniques},
	booktitle = {IEEE 7th International Conference on Research Challenges in Information Science (RCIS)},
	year = {2013},
	month = {may},
	publisher = {IEEE},
	organization = {IEEE},
	abstract = {WS-BPEL has been adopted as the predominant method for composing individual web services into higher-level business processes. The designers of WS-BPEL scenarios define at development time the specific web services that will be invoked in the context of the business process they model; in the context however of the current web, where each functionality is offered by multiple service providers, under different quality of service parameters, using a fixed BPEL scenario has been recognized to be inadequate for servicing the diverse needs of business processes clients. To this end, WS-BPEL scenario execution adaptation has been proposed, mainly allowing clients to specify quality of service policies, which drive the dynamic selection of the services that will be invoked. In this paper, we present a framework extending the quality of service-based adaptation mechanisms with collaborative filtering techniques, allowing clients to further refine the adaptation process by considering service selections made by other clients, in the context of the same business processes.},
	doi = {10.1109/rcis.2013.6577691},
	author = {Dionisis Margaris and P. Georgiadis and Costas Vassilakis}
}
@conference {Margaris2013SAC,
	title = {An integrated framework for QoS-based adaptation and exception resolution in WS-BPEL scenarios},
	booktitle = {Proceedings of the 28th Annual ACM Symposium on Applied Computing - SAC \textquotesingle13},
	year = {2013},
	month = {3},
	publisher = {ACM Press},
	organization = {ACM Press},
	abstract = {In this paper, we present a framework which incorporates runtime quality of service-based adaptation for BPEL scenarios, allowing for tailoring their execution to the diverse needs of individual users. The proposed framework also caters for automatically resolving system-level exceptions, such as machine outages or network partitionings, while both scenario execution adaptation and exception resolution maintain the transactional semantics that invocations to multiple services offered by the same provider may bear.},
	doi = {10.1145/2480362.2480714},
	author = {Dionisis Margaris and Costas Vassilakis and P. Georgiadis}
}
@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}
}
@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}
}
@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 {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 {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 {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 {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}
}
@article {Vassilakis200581,
	title = {Exploiting form semantics and validation checks to improve e-form layout},
	journal = {International Journal of Web Engineering and Technology},
	volume = {2},
	number = {1},
	year = {2005},
	note = {cited By (since 1996) 0},
	pages = {81-96},
	abstract = {On their route to the electronic era, organisations release on the web more and more complex form-based services, which require users to enter numerous data items interrelated by business rules. In such a context, it is crucial to provide optimal form layouts, in order to present the service users with interfaces that facilitate their work. This paper presents an integrated environment, which exploits data item interrelations manifested by the business rules (or validation checks), to optimise the layout of the web forms comprising a complex service. The approach is validated through its application on a tax return form e-service. Copyright Β{\textcopyright} 2005 Inderscience Enterprises Ltd.},
	keywords = {electronic services, Form layout, Form semantics, Integrated environment, Interfaces (computer), Optimization, semantics, Taxation, Usuability, Validation checks, World Wide Web},
	doi = {10.1504/IJWET.2005.007465},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-24344507764\&partnerID=40\&md5=e94b487785303410cb7bf88df9d12c86},
	author = {Costas Vassilakis and Giorgos Lepouras and S. Rouvas and P. Georgiadis}
}
@conference {Vassilakis2005421,
	title = {A semantics-based consultations workbench},
	booktitle = {ITI 3rd International Conference on Information and Communications Technology, ICICT 2005 - Enabling Technologies for the New Knowledge Society},
	volume = {2005},
	year = {2005},
	note = {cited By (since 1996) 0},
	month = {12},
	pages = {421-434},
	abstract = {Econsultations constitute an effective means to inclusive and informed participation of citizens and society in policy, decision and law formulation processes, and an answer to democratic deficit issues. Econsultation platforms need to support all stages of consultation processes including agenda setting and topics raising, legislation proposal publicity, notification of developments, proposal debate and commentary, collection, analysis and synthesis of views. In this paper we present the design of an open platform assisting policy makers and the civil society in the set-up, enactment, management and federation of inclusive and informed digital consultations. The proposed platform employs semantic techniques, such as semantics, content annotation and summarization to support the consultation processes and provide targeted and digested information to participants, and facilitates tailoring of Econsultation procedures by offering basic Econsultation activities as building blocks, which can be combined according to contextual needs. The platform also enables distinct Econsultation processes to be federated, allowing the exchange of information, which may be subject to different semantic annotations and classifications, according to the rules of each Econsultation process.},
	keywords = {Classification (of information), Content annotation, Data transfer, Decision making, Econsultations, Knowledge based systems, Logic programming, Platform architecture, Public policy, Semantic technologies, semantics},
	doi = {10.1109/ITICT.2005.1609641},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-33847729948\&partnerID=40\&md5=54c7a246c0ee9ae483889741a327253b},
	author = {Costas Vassilakis and D. Gouscos and P. Georgiadis}
}
@article {DBLP:journals/eg/VassilakisLRG04,
	title = {Integrating e-government public transactional services into public authority workflows},
	journal = {Electronic Government},
	volume = {1},
	number = {1},
	year = {2004},
	pages = {49-60},
	abstract = {Documents submitted by citizens through electronic services deployed in the context of e-Government must usually undergo processing by some organisational information system, in order to complete the citizens? requests and for the reply to be returned to the citizen. The integration, however, of the e-service delivery platform and the organisational information system is often hindered for a number of reasons, including security considerations, platform diversity or idiosyncrasies of legacy information systems. In this paper we present a generic method for providing seamless communication between the two platforms, enabling the full integration of documents submitted through electronic services into the organisational workflow, leveraging thus the quality of services offered to the citizens and facilitating e-service development and operation.},
	doi = {10.1504/EG.2004.004136},
	author = {Costas Vassilakis and Giorgos Lepouras and S. Rouvas and P. Georgiadis}
}
@article {Vassilakis2003315,
	title = {A framework for managing the lifecycle of transactional e-government services},
	journal = {Telematics and Informatics},
	volume = {20},
	number = {4},
	year = {2003},
	note = {cited By (since 1996) 13},
	pages = {315-329},
	abstract = {Filling and submission of electronic forms is a key issue for e-government, since most electronic services offered in this context include some variant of electronic forms. Insofar, IT experts are placed in the centre of electronic forms services lifecycles, undertaking the analysis, design, implementation and maintenance phases. This practice, however, implies various impediments, such as the need for multitudinous teams with diverse skills. In this paper, we present experiences from developing and maintaining a set of electronic services for the Greek Ministry of Finance, and propose an approach to handling electronic services{\textquoteright} lifecycle that balances responsibilities between domain experts and IT professionals. This approach enables a more holistic management of the electronic service lifecycle, by employing modelling and representation in high levels of abstraction and incorporating tools for automatically generating operative service instances from these high-level descriptions. Β{\textcopyright} 2003 Elsevier Science Ltd. All rights reserved.},
	keywords = {Communication, Electronic forms, Information science, Information technology},
	doi = {10.1016/S0736-5853(03)00011-X},
	url = {https://www.sciencedirect.com/science/article/abs/pii/S073658530300011X},
	author = {Costas Vassilakis and Laskaridis, G. and Giorgos Lepouras and S. Rouvas and P. Georgiadis}
}
@conference {DBLP:conf/caise/VassilakisLRG03,
	title = {Improving e-Form Layout Through Analysis of Form Semantics and Validation Checks},
	booktitle = {CAiSE Short Paper Proceedings},
	year = {2003},
	month = {6},
	abstract = {Transaction services offered by public authorities vary from simple forms with few fields to multi-form compound documents with hundreds of input areas. In the latter case, field placement within forms is of particular importance for facilitating the filling and error correction processes. In this paper we present an approach to improving the form layout by exploiting validation checks that are usually associated with electronic forms, as well as semantic information that may be attached to form fields by designers.},
	url = {http://ceur-ws.org/Vol-74/files/FORUM_38.pdf},
	author = {Costas Vassilakis and Giorgos Lepouras and S. Rouvas and P. Georgiadis}
}
@conference {667640,
	title = {An Object-Oriented Approach for Designing Administrative E-forms and Transactional E-services},
	booktitle = {OOIS {\textquoteright}02: Proceedings of the 8th International Conference on Object-Oriented. Information Systems},
	year = {2002},
	month = {9},
	pages = {19{\textendash}30},
	publisher = {Springer-Verlag},
	organization = {Springer-Verlag},
	address = {London, UK},
	abstract = {Although electronic transaction services are considered to be a necessity for e-government, it has not been possible insofar to unleash their full potential. E-forms are central to the development of e-government, being a basic means for implementing the majority of the public services considered as required for local and central public administration authorities. In this paper, we present an object-oriented model for e-form-based administrative services, which spans the e-service lifecycle, including development, deployment and use by enterprises and citizens, data collection and communication with legacy information systems. The proposed approach encompasses semantic, structural and active aspects of e-forms, providing thus an inclusive framework for modelling electronic services.},
	isbn = {3-540-44087-9},
	doi = {10.1007/3-540-46102-7_6},
	author = {D. Gouscos and S. Rouvas and Costas Vassilakis and P. Georgiadis}
}
@conference {Georgiadis_2002,
	title = {SmartGov: A Knowledge-Based Platform for Transactional Electronic Services},
	booktitle = {Lecture Notes in Computer Science},
	year = {2002},
	month = {9},
	pages = {362-369},
	publisher = {Springer Berlin Heidelberg},
	organization = {Springer Berlin Heidelberg},
	abstract = {Public transaction services (such as e-forms) although perceived the future of e-government have not yet realised their full potential. E-forms have a significant role in e-government, as they are the basis for implementing most of the twenty public services that all member states have to provide to their citizens and businesses. The aim of the SmartGov project is to specify, develop, deploy and evaluate a knowledge-based platform to assist public sector employees to generate online transaction services by simplifying their development, maintenance and integration with already installed IT systems. This platform will be evaluated in two European countries (in one Ministry and one Local Authority). This paper outlines key issues in the development of the SmartGov system platform.},
	doi = {10.1007/978-3-540-46138-8_59},
	url = {https://link.springer.com/chapter/10.1007/978-3-540-46138-8_59},
	author = {P. Georgiadis and Giorgos Lepouras and Costas Vassilakis and G. Boukis and E. Tambouris and S. Gorilas and E. Davenport and A. Macintosh and J. Fraser and D. Lochhead}
}
@conference {650426,
	title = {Transactional e-Government Services: An Integrated Approach},
	booktitle = {EGOV {\textquoteright}02: Proceedings of the First International Conference on Electronic Government},
	year = {2002},
	month = {9},
	pages = {276{\textendash}279},
	publisher = {Springer-Verlag},
	organization = {Springer-Verlag},
	address = {London, UK},
	abstract = {Although form-based transactional services are fundamental to electronic government activities, their widespread does neither meet the citizen{\textquoteright}s expectations, nor the potential offered by state-of-the-art technologies. Besides any bureaucratic impediments, the primary reason for this is that traditional software engineering approaches cannot satisfactorily handle all the aspects of electronic services lifecycle. In this paper we present experiences from developing and maintaining a set of electronic services for the Greek Ministry of Finance, and propose a new approach for handling electronic service projects. The proposed approach has been successfully employed for developing extensions to the existing services, as well as some new ones.},
	isbn = {3-540-44121-2},
	doi = {10.1007/978-3-540-46138-8_44},
	url = {http://link.springer.com/chapter/10.1007\%2F978-3-540-46138-8_44},
	author = {Costas Vassilakis and Laskaridis, G. and Giorgos Lepouras and S. Rouvas and P. Georgiadis}
}
@article {Vassilakis1998335,
	title = {Implementation of transaction and concurrency control support in a temporal DBMS},
	journal = {Information Systems},
	volume = {23},
	number = {5},
	year = {1998},
	note = {cited By (since 1996) 2},
	pages = {335{\textendash}350},
	abstract = {Transactions and concurrency control are significant features in database systems, facilitating functions both at user and system level. However, the support of these features in a temporal DBMS has not yet received adequate research attention. In this paper, we describe the techniques developed in order to support transaction and concurrency control in a temporal DBMS that was implemented as an additional layer to a commercial DBMS. The proposed techniques make direct use of the transaction mechanisms of the DBMS. In addition, they overcome a number of limitations such as automatic commit points, lock release and log size increment, which are imposed by the underlying DBMS. Our measurements have shown that the overhead introduced by these techniques is negligible, less than 1\% in all cases. The approach undertaken is of general interest, it can also be applied to non-temporal DBMS extensions. Copyright Β{\textcopyright} 1998 Elsevier Science Ltd. All rights reserved.},
	keywords = {Concurrency control, Data structures, Database systems, Temporal databases},
	doi = {10.1016/S0306-4379(98)00015-5},
	url = {https://doi.org/10.1016/S0306-4379(98)00015-5},
	author = {Costas Vassilakis and N. Lorentzos and P. Georgiadis}
}
@conference {754888,
	title = {Implementing Embedded Valid Time Query Languages},
	booktitle = {DEXA {\textquoteright}98: Proceedings of the 9th International Conference on Database and Expert Systems Applications},
	year = {1998},
	month = {8},
	pages = {561{\textendash}572},
	publisher = {Springer-Verlag},
	organization = {Springer-Verlag},
	address = {London, UK},
	abstract = {Application development on top of database systems is heavily based on the existence of embedded and 4GL languages. However, the issue of designing and implementing embedded or 4GL temporal languages has not been addressed insofar. In this paper, we present a design approach for implementing an embedded temporal language that supports valid time. Furthermore, we introduce implementation techniques that can be used for implementing any embedded temporal language that supports valid time on top of a DBMS.},
	isbn = {3-540-64950-6},
	doi = {10.1007/BFb0054514},
	author = {Costas Vassilakis and P. Georgiadis and Sellis, Timos K.}
}
@conference {790099,
	title = {A comparative study of temporal DBMS architectures},
	booktitle = {DEXA {\textquoteright}96: Proceedings of the 7th International Workshop on Database and Expert Systems Applications},
	year = {1996},
	month = {9},
	pages = {153},
	publisher = {IEEE Computer Society},
	organization = {IEEE Computer Society},
	address = {Washington, DC, USA},
	abstract = {In the past years, a number of implementations of temporal DBMSs has been reported. Most of these implementations share a common feature, which is that they have been built as an extension to a snapshot DBMS. In this paper, we present three alternative design approaches that can be used for extending a snapshot DBMS to support temporal data,and evaluate the suitability of each approach, with respect to a number of design objectives.},
	isbn = {0-8186-7662-0},
	doi = {10.1109/DEXA.1996.558289},
	author = {Costas Vassilakis and P. Georgiadis and Anya Sotiropoulou}
}
@conference {719700,
	title = {Transaction Support in a Temporal DBMS},
	booktitle = {Proceedings of the International Workshop on Temporal Databases},
	year = {1995},
	month = {9},
	pages = {255{\textendash}271},
	publisher = {Springer-Verlag},
	organization = {Springer-Verlag},
	address = {London, UK},
	abstract = {Transactions are a significant concept in database systems, facilitating functions both at user and system level. However transaction support in temporal DBMSs has not yet received enough research attention. In this paper, we present techniques for incorporating transaction support in a temporal DBMS, which is implemented as an additional layer to a commercial RDBMS. These techniques overcome certain limitations imposed by the underlying RDBMS, and avoid excessive increment of the log size.},
	isbn = {3-540-19945-4},
	doi = {10.1007/978-1-4471-3033-8_14},
	url = {http://link.springer.com/chapter/10.1007\%2F978-1-4471-3033-8_14},
	author = {Costas Vassilakis and N. Lorentzos and P. Georgiadis}
}
@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.}
}
@conference {1993-boukouvalas-hci,
	title = {An Enhanced System for File Access in a Distributed UNIX Environment},
	booktitle = {Proceedings of the 4th Hellenic Conference on Informatics},
	year = {1993},
	month = {12},
	abstract = {In this study we present an Enhanced File System for a Distributed Unix Environment. The Enhanced Unix File System implements a flexible protection mechanism for files and directories. It is based on the concept of Access Control Lists (ACL), which allows different permissions for files and directories to be given to specific users. His work was developed under the SunOS/NFS distributed environment, using Remote Procedure Calls (RPC) to implement the communication between the client and the server. The system consists of a daemon process working as a server and a set of client processes that provide different file and directory services. There may be running many different servers and clients over the same network. The client processes transparently locate the appropriate server for each transaction. The system also provides an open programming environment for the development of new applications. Both the user and the programmer interface of the system are kept close to standard UNIX.},
	url = {http://cst.uop.gr/images/papers/1993-kassapidis-hci.pdf},
	author = {Boucouvalas, C. and Costas Vassilakis and P. Georgiadis}
}
@conference {1993-vassilakis-hci,
	title = {A Methodology for the Implementation of Software for the Design of Distributed Systems},
	booktitle = {Proceedings of the 4th Hellenic Conference on Informatics},
	year = {1993},
	month = {12},
	pages = {673{\textendash}686},
	abstract = {As the use of distributed systems is spreading, and applications designed for such systems become more and more demanding, optimal design of distributed systems becomes a critical issue. Designing a distributed system has become more complex, due to the number of alternatives for each decision that must be made and because of the existence of many parameters which influence the overal performance of the distributed system. Thus, it is necessary to use software tools, capable of accepting a description of the user{\textquoteright}s requirements and suggesting solutions to the problem of designing a distributed system which meets the user{\textquoteright}s requirements. In this paper, we present a disciplined approach to the construction of such a software tool, which combines methods from the Artificial Intelligence domain, that are used in order to design the distributed system, along with simulation techniques, used to estimate the system{\textquoteright}s overall performance.},
	author = {Costas Vassilakis and P. Georgiadis and D. Lelis and D. Mouzakis and M. Nikolaidou}
}
