Fragkiskos Pentaris

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Commercially available interpersonal communication aids appear to lack a common technical ground to facilitate both user-adaptation and functional flexibility. The framework of an alternative solution is presented in this paper, concerning a novel approach aiming to affect the development of interpersonal communication systems. It utilises a new, open and(More)
Complex on-demand data retrieval and processing is a characteristic of several applications and combines the notions of querying & search, information filtering & retrieval, data transformation & analysis, and other data manipulations. Such rich tasks are typically represented by data processing graphs, having arbitrary data operators as nodes and their(More)
Large-scale distributed environments, where each node is completely autonomous and offers services to its peers through external communication, pose significant challenges to query processing and optimization. Autonomy is the main source of the problem, as it results in lack of knowledge about any particular node with respect to the information it can(More)
There is a growing demand for more cost-efficient production processes in Statistical Institutes. One way to address this need is to equip Statistical Information Systems (SIS) with the ability to automatically produce statistical data and metadata of high quality and deliver them to the user via the Internet. Current approaches, although provide for the(More)
In large federations of autonomous database systems, automatic distribution of the query workload to those systems is a critical issue. We examine this problem under the perspective of microeconomics theory and show how the latter can be used to construct an efficient decentralized mechanism that maximizes system throughput. In particular, we introduce a(More)
We introduce a statistical, process-oriented metadata model to describe the process of medical research data collection, management, results analysis and dissemination. Our approach explicitly provides a structure for pieces of information used in Clinical Study Data Management Systems, enabling a more active role for any associated metadata. Using the(More)
The advantages of collecting structured metadata are presented and various ways of storing metainformation are discussed. An example of a statistical metadata model is given using the Unified Modelling Language (UML) and properties and semantics of this model are further examined. The simultaneous manipulation of both data and metadata is discussed by(More)