Nikos Papadakis

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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)
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)
The ramiication 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 ramiication problem. In this paper, we address the ramiication problem based on causal relationships that take t i m e i n to account. We study the problem for both(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)
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)
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 assumptions that fluents persist and actions have effects on the subsequent situation only. We provide a solution based on an extension of the situation calculus and(More)