Nikos Papadakis

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We introduce TOQL, a query language for querying time information in ontologies. TOQL is a high level query language that handles ontologies almost like relational databases. Queries are issued as SQL-like statements involving time (i.e., time points or intervals) or high-level ontology concepts that vary in time. Although independent from TOQL, this work(More)
Maternal exposure to environmental tobacco smoke (ETS) is a major health hazard as it contains lower doses of the toxins that smokers’ inhale. Prenatal exposure to wood fuel smoke has been linked to delivering low birth weight (LBW) infants. The study aims to assess the association between prenatal exposure to ETS and wood fuel smoke and LBW. A case–control(More)
The ramification problem is a hard and ever present problem in systems exhibiting a dynamic behavior. The area of temporal databases in particular is still lacking satisfactory solutions to the ramification problem. In this paper, we address the ramification problem based on causal relationships that take time into account. We study the problem for both(More)
We present PROTON, a reasoner for managing temporal information over OWL ontologies. We adopt the so called 4d-fluent or 4-dimensionalist approach for representing temporal information in ontologies ie. for time points or intervals and for events that occur in time points or intervals. Also, we propose an extension to the situation calculus in order to(More)
Reasoning about action and change has been one of the main research themes of the knowledge representation and planning communities of the last years Action theories providing an axiomatic basis for managing change are applicable to a wide area of disciplines including software engi neering cognitive robotics and data knowledge base systems In this paper we(More)
The procedure to prove that a system-of-systems is composable and secure is a very difficult task. Formal methods are mathematically-based techniques used for the specification, development and verification of software and hardware systems. This paper presents a model-based framework for dynamic embedded system composition and security evaluation. Event(More)
In this paper we elaborate on the handling of the ramification problem in the setting of temporal databases. Starting with the observation that solutions from the literature on reasoning about action are inadequate for addressing the ramification problem, in our prior work (Papadakis and Plexousakis in Int. J. Artif. Intel., 12(3):315, 2003) we have(More)
Many DB management systems use SQL syntax in order to provide a mechanism for data accessing. Although SQL is widely used, its syntax is not very comprehensive to a typical user. In this paper we present a tool capable of transforming simple queries formatted in natural language into their equivalent SQL queries. The purpose of this study is to provide a(More)
In this paper we study the ramification problem in the setting of temporal databases. Standard solutions from the literature on reasoning about action are inadequate because they rely on the assumption that fluents persist, and because actions have effects on the next situation only. In this paper we provide a solution to the ramification problem based on(More)