700 research outputs found
Four Lessons in Versatility or How Query Languages Adapt to the Web
Exposing not only human-centered information, but machine-processable data on the Web is one of the commonalities of recent Web trends. It has enabled a new kind of applications and businesses where the data is used in ways not foreseen by the data providers. Yet this exposition has fractured the Web into islands of data, each in different Web formats: Some providers choose XML, others RDF, again others JSON or OWL, for their data, even in similar domains. This fracturing stifles innovation as application builders have to cope not only with one Web stack (e.g., XML technology) but with several ones, each of considerable complexity. With Xcerpt we have developed a rule- and pattern based query language that aims to give shield application builders from much of this complexity: In a single query language XML and RDF data can be accessed, processed, combined, and re-published. Though the need for combined access to XML and RDF data has been recognized in previous work (including the W3Câs GRDDL), our approach differs in four main aspects: (1) We provide a single language (rather than two separate or embedded languages), thus minimizing the conceptual overhead of dealing with disparate data formats. (2) Both the declarative (logic-based) and the operational semantics are unified in that they apply for querying XML and RDF in the same way. (3) We show that the resulting query language can be implemented reusing traditional database technology, if desirable. Nevertheless, we also give a unified evaluation approach based on interval labelings of graphs that is at least as fast as existing approaches for tree-shaped XML data, yet provides linear time and space querying also for many RDF graphs. We believe that Web query languages are the right tool for declarative data access in Web applications and that Xcerpt is a significant step towards a more convenient, yet highly efficient data access in a âWeb of Dataâ
An order-theoretic characterization of the Howard-Bachmann-hierarchy
In this article we provide an intrinsic characterization of the famous Howard-Bachmann ordinal in terms of a natural well-partial-ordering by showing that this ordinal can be realized as a maximal order type of a class of generalized trees with respect to a homeomorphic embeddability relation. We use our calculations to draw some conclusions about some corresponding subsystems of second order arithmetic. All these subsystems deal with versions of light-face Î âÂč-comprehension
On the strength of the finite intersection principle
We study the logical content of several maximality principles related to the
finite intersection principle (F\IP) in set theory. Classically, these are
all equivalent to the axiom of choice, but in the context of reverse
mathematics their strengths vary: some are equivalent to \ACA over \RCA,
while others are strictly weaker, and incomparable with \WKL. We show that
there is a computable instance of F\IP all of whose solutions have
hyperimmune degree, and that every computable instance has a solution in every
nonzero c.e.\ degree. In terms of other weak principles previously studied in
the literature, the former result translates to F\IP implying the omitting
partial types principle (). We also show that, modulo
induction, F\IP lies strictly below the atomic model theorem
().Comment: This paper corresponds to section 3 of arXiv:1009.3242, "Reverse
mathematics and equivalents of the axiom of choice", which has been
abbreviated and divided into two pieces for publicatio
Observation of the Decay Î0bâÎ+cÏâÂŻÎœ
The first observation of the semileptonic b-baryon decay Îb0âÎc+Ï-ÎœÂŻÏ, with a significance of 6.1Ï, is reported using a data sample corresponding to 3 fb-1 of integrated luminosity, collected by the LHCb experiment at center-of-mass energies of 7 and 8 TeV at the LHC. The Ï- lepton is reconstructed in the hadronic decay to three charged pions. The ratio K=B(Îb0âÎc+Ï-ÎœÂŻÏ)/B(Îb0âÎc+Ï-Ï+Ï-) is measured to be 2.46±0.27±0.40, where the first uncertainty is statistical and the second systematic. The branching fraction B(Îb0âÎc+Ï-ÎœÂŻÏ)=(1.50±0.16±0.25±0.23)% is obtained, where the third uncertainty is from the external branching fraction of the normalization channel Îb0âÎc+Ï-Ï+Ï-. The ratio of semileptonic branching fractions R(Îc+)B(Îb0âÎc+Ï-ÎœÂŻÏ)/B(Îb0âÎc+ÎŒ-ÎœÂŻÎŒ) is derived to be 0.242±0.026±0.040±0.059, where the external branching fraction uncertainty from the channel Îb0âÎc+ÎŒ-ÎœÂŻÎŒ contributes to the last term. This result is in agreement with the standard model prediction
Study of the psi(2)(3823) and chi(c1)(3872) states in B+->(J/psi pi(+)pi(-))K(+)decays
The decays are studied using a data
set corresponding to an integrated luminosity of 9fb collected with the
LHCb detector in proton-proton collisions between 2011 and 2018. Precise
measurements of the ratios of branching fractions with the intermediate
, and states are reported. The decay
of with is observed for the first time with a significance of 5.1
standard deviations. The mass differences between the ,
and states are measured to be resulting in the
most precise determination of the mass. The width of the
state is found to be below 5.2MeV at 90\% confidence level. The
Breit-Wigner width of the state is measured to be which is inconsistent with zero by 5.5 standard deviations.Comment: 26 pages, 3 figures. All figures and tables, along with any
supplementary material and additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2020-009.html (LHCb
public pages
Measurement of antiproton production from antihyperon decays in pHe collisions at âsNN=110GeV
The interpretation of cosmic antiproton flux measurements from space-borne experiments is currently limited by the knowledge of the antiproton production cross-section in collisions between primary cosmic rays and the interstellar medium. Using collisions of protons with an energy of 6.5 TeV incident on helium nuclei at rest in the proximity of the interaction region of the LHCb experiment, the ratio of antiprotons originating from antihyperon decays to prompt production is measured for antiproton momenta between 12 and 110GeV\!/c . The dominant antihyperon contribution, namely ÎÂŻ â pÂŻ Ï+ decays from promptly produced ÎÂŻ particles, is also exclusively measured. The results complement the measurement of prompt antiproton production obtained from the same data sample. At the energy scale of this measurement, the antihyperon contributions to antiproton production are observed to be significantly larger than predictions of commonly used hadronic production models
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