2,465 research outputs found
Reasoning about exceptions in ontologies: from the lexicographic closure to the skeptical closure
Reasoning about exceptions in ontologies is nowadays one of the challenges
the description logics community is facing. The paper describes a preferential
approach for dealing with exceptions in Description Logics, based on the
rational closure. The rational closure has the merit of providing a simple and
efficient approach for reasoning with exceptions, but it does not allow
independent handling of the inheritance of different defeasible properties of
concepts. In this work we outline a possible solution to this problem by
introducing a variant of the lexicographical closure, that we call skeptical
closure, which requires to construct a single base. We develop a bi-preference
semantics semantics for defining a characterization of the skeptical closure
A reconstruction of the multipreference closure
The paper describes a preferential approach for dealing with exceptions in
KLM preferential logics, based on the rational closure. It is well known that
the rational closure does not allow an independent handling of the inheritance
of different defeasible properties of concepts. Several solutions have been
proposed to face this problem and the lexicographic closure is the most notable
one. In this work, we consider an alternative closure construction, called the
Multi Preference closure (MP-closure), that has been first considered for
reasoning with exceptions in DLs. Here, we reconstruct the notion of MP-closure
in the propositional case and we show that it is a natural variant of Lehmann's
lexicographic closure. Abandoning Maximal Entropy (an alternative route already
considered but not explored by Lehmann) leads to a construction which exploits
a different lexicographic ordering w.r.t. the lexicographic closure, and
determines a preferential consequence relation rather than a rational
consequence relation. We show that, building on the MP-closure semantics,
rationality can be recovered, at least from the semantic point of view,
resulting in a rational consequence relation which is stronger than the
rational closure, but incomparable with the lexicographic closure. We also show
that the MP-closure is stronger than the Relevant Closure.Comment: 57 page
Defeasible Reasoning in SROEL: from Rational Entailment to Rational Closure
In this work we study a rational extension of the low complexity
description logic SROEL, which underlies the OWL EL ontology language. The
extension involves a typicality operator T, whose semantics is based on Lehmann
and Magidor's ranked models and allows for the definition of defeasible
inclusions. We consider both rational entailment and minimal entailment. We
show that deciding instance checking under minimal entailment is in general
-hard, while, under rational entailment, instance checking can be
computed in polynomial time. We develop a Datalog calculus for instance
checking under rational entailment and exploit it, with stratified negation,
for computing the rational closure of simple KBs in polynomial time.Comment: Accepted for publication on Fundamenta Informatica
On the KLM properties of a fuzzy DL with Typicality
The paper investigates the properties of a fuzzy logic of typicality. The
extension of fuzzy logic with a typicality operator was proposed in recent work
to define a fuzzy multipreference semantics for Multilayer Perceptrons, by
regarding the deep neural network as a conditional knowledge base. In this
paper, we study its properties. First, a monotonic extension of a fuzzy ALC
with typicality is considered (called ALC^FT) and a reformulation the KLM
properties of a preferential consequence relation for this logic is devised.
Most of the properties are satisfied, depending on the reformulation and on the
fuzzy combination functions considered. We then strengthen ALC^FT with a
closure construction by introducing a notion of faithful model of a weighted
knowledge base, which generalizes the notion of coherent model of a conditional
knowledge base previously introduced, and we study its properties.Comment: 15 page
Surveillance of paediatric exposures to liquid laundry detergent pods in Italy
Objective To analyse paediatric exposures to pod and traditional laundry detergents in Italy and changes in exposure trends.
Methods Analyses of a series of patients aged <5 years and exposed to laundry detergents between September 2010 and June 2015, identified by the National Poison Control in Milan.
Results In comparison with patients exposed to traditional laundry detergents (n=1150), a higher proportion of those exposed to pods (n=1649) were managed in hospital (68% vs 42%), had clinical effects (75% vs 22%) and moderate/high severity outcomes (13% vs <1%). Exposure rates were stable over time for traditional detergents (average 0.65 cases/day), but an abrupt decline in major company pods was seen in December 2012, 4 months after the introduction of opaque outer packaging (from 1.03 to 0.36 cases/day and from 1.88 to 0.86 cases/million units sold). The odds of clinical effects was higher for exposure to pods than for traditional detergents (OR=10.8; 95% CI 9.0 to 12.9). Among patients exposed to pods, the odds of moderate/high severity outcomes was four times higher for children aged <1 years than for the other age groups (OR=3.9; 95% CI 2.2 to 7.0). Ten children exposed to laundry detergent pods had high severity outcomes while no children exposed to traditional laundry detergents developed high severity effects.
Conclusions The study confirms that exposure to laundry detergent pods is more dangerous than exposure to traditional detergents. In Italy, 4 months after the introduction of opaque outer packaging by a major company, product-specific exposure rates decreased sharply, suggesting that reducing visibility of laundry detergent pods may be an effective preventive measure. Further efforts are needed to improve safety
Reseñas
Obra ressenyada: Mònica BALLTONDRE, Éxtasis y visiones: la experiencia contemplativa de Teresa de Ávila. Vilafranca de Penedès; Barcelona: Erasmus, 2012
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