Francesco Buccafurri

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The paper proposes a new knowledge representation language, called DLP, which extends disjunctive logic programming (with strong negation) by inheritance. The addition of inheritance enhances the knowledge modeling features of the language providing a natural representation of default reasoning with exceptions. A declarative model-theoretic semantics of DLP(More)
In this paper we propose a logic formalism that naturally supports the encoding of complex security specifications. This formalism relies on a hierarchically structured domain made of subjects, objects and privileges. Authorizations are expressed by logic rules. The formalism supports both negation by failure (possibly unstratified) and true negation. The(More)
Model checking is a fruitful application of computational logic with high relevance to the verification of concurrent systems. While model checking is capable of automatically testing that a concurrent system satisfies its formal specification, it can not precisely locate an error and suggest a repair, i.e., a suitable correction, to the system. In this(More)
Histograms are used to summarize the contents of relations for the estimation of query result sizes into a number of buckets. Several techniques (e.g., MaxDiff and VOptimal) have been proposed in the past for determining bucket boundaries which provide better estimations. This paper proposes to use a 32-bit information (4-level tree index) for each bucket(More)
The paper proposes a knowledge representation language which extends logic programming with disjunction, inheritance, true negation and modularization. The resulting language is called Disjunctive Ordered Logic ( $$\mathcal{D}\mathcal{O}\mathcal{L}$$ for short). A model‐theoretic semantics for $$\mathcal{D}\mathcal{O}\mathcal{L}$$ is given, and it is shown(More)
E> Previous researchers have proposed extensions of logic programming to deal with true negation and defeasible reasoning. Ordered Logic ((9£:) achieves both such goals by allowing rules with negated heads in the context of an inheritance hierarchy. As a result, (9£: is inherently nonmonotonic. Another area of interest in logic programming is that dealing(More)
In many application contexts, like statistical databases, scientific databases, query optimizers, OLAP, and so on, data are often summarized into synopses of aggregate values. Summarization has the great advantage of saving space, but querying aggregate data rather than the original ones introduces estimation errors which cannot be in general avoided, as(More)
In case an ACTL formula fails over a transition graph M , it is most useful to provide a counterexample, i.e., a computation tree of M witnessing the failure. If there exists a single path in M which by itself witnesses the failure of , then has a linear counterexample. We show that, given M and , where M 6j= , it is NP-hard to determine whether there(More)