7,427 research outputs found
Adding DL-Lite TBoxes to Proper Knowledge Bases
Levesque’s proper knowledge bases (proper KBs) correspond to infinite sets of ground positive and negative facts, with the notable property that for FOL formulas in a certain normal form, which includes conjunctive queries and positive queries possibly extended with a controlled form of negation, entailment reduces to formula evaluation. However proper KBs represent extensional knowledge only. In description logic terms, they correspond to ABoxes. In this paper, we augment them with DL-Lite TBoxes, expressing intensional knowledge (i.e., the ontology of the domain). DL-Lite has the notable property that conjunctive query answering over TBoxes and standard description logic ABoxes is re- ducible to formula evaluation over the ABox only. Here, we investigate whether such a property extends to ABoxes consisting of proper KBs. Specifically, we consider two DL-Lite variants: DL-Literdfs , roughly corresponding to RDFS, and DL-Lite_core , roughly corresponding to OWL 2 QL. We show that when a DL- Lite_rdfs TBox is coupled with a proper KB, the TBox can be compiled away, reducing query answering to evaluation on the proper KB alone. But this reduction is no longer possible when we associate proper KBs with DL-Lite_core TBoxes. Indeed, we show that in the latter case, query answering even for conjunctive queries becomes coNP-hard in data complexity
Some results on the Zeeman topology
In a 1967 paper, Zeeman proposed a new topology for Minkowski spacetime,
physically motivated but much more complicated than the standard one. Here a
detailed study is given of some properties of the Zeeman topology which had not
been considered at the time. The general setting refers to Minkowski spacetime
of any dimension k+1. In the special case k=1, a full characterization is
obtained for the compact subsets of spacetime; moreover, the first homotopy
group is shown to be nontrivial.Comment: Part of my Laurea thesis. REVTeX4. Minor changes from previous
versio
Service composition in stochastic settings
With the growth of the Internet-of-Things and online Web services, more services with more capabilities are available to us. The ability to generate new, more useful services from existing ones has been the focus of much research for over a decade. The goal is, given a specification of the behavior of the target service, to build a controller, known as an orchestrator, that uses existing services to satisfy the requirements of the target service. The model of services and requirements used in most work is that of a finite state machine. This implies that the specification can either be satisfied or not, with no middle ground. This is a major drawback, since often an exact solution cannot be obtained. In this paper we study a simple stochastic model for service composition: we annotate the tar- get service with probabilities describing the likelihood of requesting each action in a state, and rewards for being able to execute actions. We show how to solve the resulting problem by solving a certain Markov Decision Process (MDP) derived from the service and requirement specifications. The solution to this MDP induces an orchestrator that coincides with the exact solution if a composition exists. Otherwise it provides an approximate solution that maximizes the expected sum of values of user requests that can be serviced. The model studied although simple shades light on composition in stochastic settings and indeed we discuss several possible extensions
How to be young at heart? miR-22 as a potential therapeutic target to boost autophagy and protect the old myocardium
Scaling of magnetic monopoles in the pure compact QED
In the pure U(1) lattice gauge theory with the Villain action we find that
the monopole mass in the Coulomb phase and the monopole condensate in the
confinement phase scale according to simple power laws. This holds outside the
coupling region in which on finite toroidal lattices the metastability
phenomena occur. A natural explanation of the observed accuracy of the scaling
behaviour would be the second order of the phase transition between both phases
in the general space of couplings not far away from the Villain action.Comment: LATTICE99(Topology and Confinement) - 3 pages, 4 fig
On the Density of Coprime m-tuples over Holomorphy Rings
Let be a finite field, be a function field of
genus having full constant field , a set of
places of and the holomorphy ring of . In this paper we
compute the density of coprime -tuples of elements of . As a side result,
we obtain that whenever the complement of is finite, the
computation of the density can be reduced to the computation of the
-polynomial of the function field. In the rational function field case,
classical results for the density of coprime -tuples of polynomials are
obtained as corollaries.Comment: To appear in International Journal of Number Theor
No-signaling, entanglement-breaking, and localizability in bipartite channels
A bipartite quantum channel represents the interaction between systems,
generally allowing for exchange of information. A special class of bipartite
channels are the no-signaling ones, which do not allow communication. In Ref.
[1] it has been conjectured that all no-signaling channels are mixtures of
entanglement-breaking and localizable channels, which require only local
operations and entanglement. Here we provide the general realization scheme,
giving a counterexample to the conjecture.Comment: 4 pages, revtex
The effects of bar-spiral coupling on stellar kinematics in the Galaxy
We investigate models of the Milky Way disc taking into account
simultaneously the bar and a two-armed quasi-static spiral pattern. Away from
major resonance overlaps, the mean stellar radial motions in the plane are
essentially a linear superposition of the isolated effects of the bar and
spirals. Thus, provided the bar is strong enough, even in the presence of
spiral arms, these mean radial motions are predominantly affected by the
Galactic bar for large scale velocity fluctuations. This is evident when
comparing the peculiar line-of-sight velocity power spectrum of our coupled
models with bar-only models. However, we show how forthcoming spectroscopic
surveys could disentangle bar-only non-axisymmetric models of the Galaxy from
models in which spiral arms have a significant amplitude. We also point out
that overlaps of low-order resonances are sufficient to enhance stellar
churning within the disc, even when the spirals amplitude is kept constant.
Nevertheless, for churning to be truly non-local, stronger or (more likely)
transient amplitudes would be needed: otherwise the disc is actually mostly
unaffected by churning in the present models. Finally, regarding vertical
breathing modes, the combined effect of the bar and spirals on vertical motions
is a clear non-linear superposition of the isolated effects of both components,
significantly superseding the linear superposition of modes produced by each
perturber separately, thereby providing an additional effect to consider when
analysing the observed breathing mode of the Galactic disc in the extended
Solar neighbourhood.Comment: 13 pages, 12 figures. MNRAS. Accepted for publication. v2 is the
published versio
- …