933 research outputs found
Discovering Restricted Regular Expressions with Interleaving
Discovering a concise schema from given XML documents is an important problem
in XML applications. In this paper, we focus on the problem of learning an
unordered schema from a given set of XML examples, which is actually a problem
of learning a restricted regular expression with interleaving using positive
example strings. Schemas with interleaving could present meaningful knowledge
that cannot be disclosed by previous inference techniques. Moreover, inference
of the minimal schema with interleaving is challenging. The problem of finding
a minimal schema with interleaving is shown to be NP-hard. Therefore, we
develop an approximation algorithm and a heuristic solution to tackle the
problem using techniques different from known inference algorithms. We do
experiments on real-world data sets to demonstrate the effectiveness of our
approaches. Our heuristic algorithm is shown to produce results that are very
close to optimal.Comment: 12 page
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Web user interface design strategy: Designing for device independence
Until recently, Web services were available only through a desktop web browser. Nowadays, methods of access move beyond the desktop computer towards ubiquitous access through portable devices. As a consequence, users have the chance to interact with a growing diversity of computing devices such as PDAs, smart phones, etc., with diverse characteristics that tend to replace conventional laptop and desktop computers. User interface designers, on the other hand, strive to design usable interfaces to cater for the diverse requirements of these devices. The design strategy proposed in this paper aims at assisting user interface designers in designing for diverse devices recommending a specific line of activities in the process of design. A case study of application of the proposed design strategy is presented, outlining its advantages
The twistor spinors of generic 2- and 3-distributions
Generic distributions on 5- and 6-manifolds give rise to conformal structures
that were discovered by P. Nurowski resp. R. Bryant. We describe both as
Fefferman-type constructions and show that for orientable distributions one
obtains conformal spin structures. The resulting conformal spin geometries are
then characterized by their conformal holonomy and equivalently by the
existence of a twistor spinor which satisfies a genericity condition. Moreover,
we show that given such a twistor spinor we can decompose a conformal Killing
field of the structure. We obtain explicit formulas relating conformal Killing
fields, almost Einstein structures and twistor spinors.Comment: 26 page
Thinking about growth : a cognitive mapping approach to understanding small business development
School of Managemen
CDMS, Supersymmetry and Extra Dimensions
The CDMS experiment aims to directly detect massive, cold dark matter
particles originating from the Milky Way halo. Charge and lattice excitations
are detected after a particle scatters in a Ge or Si crystal kept at ~30 mK,
allowing to separate nuclear recoils from the dominating electromagnetic
background. The operation of 12 detectors in the Soudan mine for 75 live days
in 2004 delivered no evidence for a signal, yielding stringent limits on dark
matter candidates from supersymmetry and universal extra dimensions. Thirty Ge
and Si detectors are presently installed in the Soudan cryostat, and operating
at base temperature. The run scheduled to start in 2006 is expected to yield a
one order of magnitude increase in dark matter sensitivity.Comment: To be published in the proceedings of the 7th UCLA symposium on
sources and detection of dark matter and dark energy in the universe, Marina
del Rey, Feb 22-24, 200
International Trade and Investment Sanctions
The purpose of this paper is to clarify the theory of international economic sanctions and to provide estimates of the short-run economic impact on South Africa of externally imposed reductions of the imports and capital flows into that country. A macroeconomic picture of South Africa's "dependence" is drawn, and the economy's vulnerability in the short run is seen to be in its capacity to import, not in exports or capital flows. Trade and capital sanctions most clearly damage South Afnca's growth potential; the short-run impact is harder to quantify. A static linear programming model of the South African economy is constructed in an attempt at this quantification. This model estimates that small sanctions would have small impactâi.e., if imports were reduced by less than one-fourth, GDP would be cut by only about one half as large a percentage as imports. Larger import reductions cause greater damage. If imports were to be cut in half, not only would GDP be seriously reduced but massive unemployment and relocation of white labor would occur.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68182/2/10.1177_002200277902300401.pd
Testing "microscopic" theories of glass-forming liquids
We assess the validity of "microscopic" approaches of glass-forming liquids
based on the sole k nowledge of the static pair density correlations. To do so
we apply them to a benchmark provided by two liquid models that share very
similar static pair density correlation functions while disp laying distinct
temperature evolutions of their relaxation times. We find that the approaches
are unsuccessful in describing the difference in the dynamical behavior of the
two models. Our study is not exhausti ve, and we have not tested the effect of
adding corrections by including for instance three-body density correlations.
Yet, our results appear strong enough to challenge the claim that the slowd own
of relaxation in glass-forming liquids, for which it is well established that
the changes of the static structure factor with temperature are small, can be
explained by "microscopic" appr oaches only requiring the static pair density
correlations as nontrivial input.Comment: 10 pages, 7 figs; Accepted to EPJE Special Issue on The Physics of
Glasses. Arxiv version contains an addendum to the appendix which does not
appear in published versio
Effective interaction between helical bio-molecules
The effective interaction between two parallel strands of helical
bio-molecules, such as deoxyribose nucleic acids (DNA), is calculated using
computer simulations of the "primitive" model of electrolytes. In particular we
study a simple model for B-DNA incorporating explicitly its charge pattern as a
double-helix structure. The effective force and the effective torque exerted
onto the molecules depend on the central distance and on the relative
orientation. The contributions of nonlinear screening by monovalent counterions
to these forces and torques are analyzed and calculated for different salt
concentrations. As a result, we find that the sign of the force depends
sensitively on the relative orientation. For intermolecular distances smaller
than it can be both attractive and repulsive. Furthermore we report a
nonmonotonic behaviour of the effective force for increasing salt
concentration. Both features cannot be described within linear screening
theories. For large distances, on the other hand, the results agree with linear
screening theories provided the charge of the bio-molecules is suitably
renormalized.Comment: 18 pages, 18 figures included in text, 100 bibliog
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