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Grammenos D.,ICS FORTH
Conference on Human Factors in Computing Systems - Proceedings

Despite the present abundance of approaches and information related to creative thinking, three basic human traits have been completely overlooked although that, if cautiously used, can considerably contribute to the creative process. Not coincidentally, these traits are also the ones that education has traditionally demonized and designated as its major enemies: stupidity, ignorance and nonsense. The aim of this paper is to shed light on the positive aspects of these defamed traits but also provide practical advice on how they can be used for sparking and nurturing creative thinking and innovative design. Source

Kritikos K.,ICS FORTH | Massonet P.,CETIC
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

Multi-cloud application management can optimize the provisioning of cloud-based applications by exploiting whole variety of services offered by cloud providers and avoiding vendor lock-in. To enable such management, model-driven approaches promise to partially automate the provisioning process. However, such approaches tend to neglect security aspects and focus only on low-level infrastructure details or quality of service aspects. As such, our previous work proposed a security meta-model, bridging the gap between high- and low-level security requirements and capabilities, able to express security models exploited by a planning algorithm to derive an optimal application deployment plan by considering both types of security requirements. This work goes one step further by focusing on runtime adaptation of multi-cloud applications based on security aspects. It advocates using adaptation rules, expressed in the event-condition-action form, which drive application adaptation behaviour and enable assuring a more-or-less stable security level. Firing such rules relies on deploying security metrics and adaptation code in the cloud to continuously monitor rule event conditions and fire adaptation actions for applications when the need arises. © Springer International Publishing Switzerland 2016. Source

Ntoutsi E.,Leibniz University of Hanover | Stefanidis K.,ICS FORTH
DDI 2016 - Proceedings of the Workshop on Data-Driven Innovation on the Web

Recommender systems have become indispensable for several Web sites, such as Amazon, Netix and Google News, helping users navigate through the abundance of available choices. Although the field has advanced impressively in the last years with respect to models, usage of heterogeneous information, such as ratings and text reviews, and recommendations for modern applications beyond purchases, almost all of the approaches rely on the data that exist within the recommender and on user explicit input. In a rapidly connected world, though, information is not isolated and does not necessarily lie in the database of a single recommender. Rather, Web offers tremendous amount of information on almost everything, from items to users and their tendency to certain items, but also information on general trends and demographics. We envision an out-of-the-box recommender system that exploits the existing information in a recommender, namely, items, users and ratings, but also explores new sources of information out of the database, like user online traces and online discussions about data items, and exploits them for better and innovative recommendations. We discuss the challenges that such an out-of-the-box approach effects and how it reshapes the field of recommenders. © 2016 ACM. Source

Bravo L.,University of Concepcion | Cheney J.,University of Edinburgh | Fundulaki I.,ICS FORTH | Segovia R.,University of Concepcion
VLDB Journal

XML access control policies involving updates may contain security flaws, here called inconsistencies, in which a forbidden operation may be simulated by performing a sequence of allowed operations. This article investigates the problem of deciding whether a policy is consistent, and if not, how its inconsistencies can be repaired. We consider total and partial policies expressed in terms of annotated schemas defining which operations are allowed or denied for the XML trees that are instances of the schema. We show that consistency is decidable in PTIME for such policies and that consistent partial policies can be extended to unique least-privilege consistent total policies. We also consider repair problems based on deleting privileges to restore consistency, show that finding minimal repairs is NP-complete, and give heuristics for finding repairs. Finally, we experimentally evaluate these algorithms in comparison with an exact approach based on answer-set programming. © 2012 Springer-Verlag. Source

Kritikos K.,ICS FORTH | Plexousakis D.,ICS FORTH
Proceedings - 2012 IEEE 19th International Conference on Web Services, ICWS 2012

Service-orientation paves the way for the Internet of Services (IoS), where millions of services will be available for building novel applications. As such, the service non-functional aspect should be considered for filtering and selecting among the great number of functionally-equivalent services that will be available for a specific user task. Until now, the state-of-the-art work in non-functional service discovery has exploited constraint solving techniques to optimize the matchmaking time between a non-functional service offer and demand pair. However, as matchmaking time is proportional to the offer number, this work does not scale well so it is not yet appropriate for the IoS. To this end, two alternative techniques are proposed to improve the overall matchmaking time. Both techniques were theoretically and experimentally evaluated. The results show that both techniques optimize the matchmaking time without sacrificing accuracy, while the second technique is quite scalable. © 2012 IEEE. Source

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