Angelos Charalambidis

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We propose a purely extensional semantics for higher-order logic programming. In this semantics program predicates denote sets of ordered tuples, and two predicates are equal iff they are equal as sets. Moreover, every program has a unique minimum Herbrand model which is the greatest lower bound of all Herbrand models of the program and the least(More)
—We describe an Inductive Logic Programming (ILP) approach to learning descriptions in Description Logics (DL) under uncertainty. The approach is based on implementing many-valued DL proofs as propositionalizations of the elementary DL constructs and then providing this implementation as background predicates for ILP. The proposed methodology is tested on a(More)
Extensional higher-order logic programming has been introduced as a generalization of classical logic programming. An important characteristic of this paradigm is that it preserves all the well-known properties of traditional logic programming. In this paper we consider the semantics of negation in the context of the new paradigm. Using some recent results(More)
The intensional transformation is a technique that can be used in order to eliminate higher-order functions from a functional program by introducing appropriate context manipulation operators. The transformation can be applied to a significant class of higher-order programs and results in equivalent zero-order intensional programs that can be executed in a(More)
Processing SPARQL queries involves the construction of an efficient <i>query plan</i> to guide query execution. Alternative plans can vary in the resources and the amount of time that they need by orders of magnitude, making planning crucial for efficiency. On the other hand, the construction of optimal plans can become computationally intensive and it also(More)
Extensional higher-order logic programming has been recently proposed as an interesting extension of classical logic programming. An important characteristic of the new paradigm is that it preserves all the well-known properties of traditional logic programming. In this paper we enhance ex-tensional higher-order logic programming with constructive negation.(More)
Dataset description vocabularies focus on provenance, ver-sioning, licensing, and similar metadata. VoID is a notable exception, providing some expressivity for describing subsets and their contents and can, to some extent, be used for discovering relevant resources and for optimizing querying. In this poster we describe an extension of VoID that provides(More)
The ability to cross-link large scale data with each other and with structured Semantic Web data, and the ability to uniformly process Semantic Web and other data adds value to both the Semantic Web and to the Big Data community. This paper presents work in progress towards integrating Big Data infrastructures with Semantic Web technologies, allowing for(More)
This paper presents work in progress towards developing a new benchmark for federated query processing systems. Unlike other popular benchmarks, our queryset is not driven by technical evaluation, but is derived from workflows established by the pharmacology community. The value of this queryset is that it is realistic but at the same time it comprises(More)
We consider the problem of concisely representing and handling preferences in logic programming and relational databases. Our starting point is a well-known proposal [8] which advocates the embedding of first-order preference formulas into relational algebra through a single <i>winnow</i> operator that is parameterized by a database relation and a(More)