188 research outputs found
Graph Interpolation Grammars: a Rule-based Approach to the Incremental Parsing of Natural Languages
Graph Interpolation Grammars are a declarative formalism with an operational
semantics. Their goal is to emulate salient features of the human parser, and
notably incrementality. The parsing process defined by GIGs incrementally
builds a syntactic representation of a sentence as each successive lexeme is
read. A GIG rule specifies a set of parse configurations that trigger its
application and an operation to perform on a matching configuration. Rules are
partly context-sensitive; furthermore, they are reversible, meaning that their
operations can be undone, which allows the parsing process to be
nondeterministic. These two factors confer enough expressive power to the
formalism for parsing natural languages.Comment: 41 pages, Postscript onl
Graph Interpolation Grammars as Context-Free Automata
A derivation step in a Graph Interpolation Grammar has the effect of scanning
an input token. This feature, which aims at emulating the incrementality of the
natural parser, restricts the formal power of GIGs. This contrasts with the
fact that the derivation mechanism involves a context-sensitive device similar
to tree adjunction in TAGs. The combined effect of input-driven derivation and
restricted context-sensitiveness would be conceivably unfortunate if it turned
out that Graph Interpolation Languages did not subsume Context Free Languages
while being partially context-sensitive. This report sets about examining
relations between CFGs and GIGs, and shows that GILs are a proper superclass of
CFLs. It also brings out a strong equivalence between CFGs and GIGs for the
class of CFLs. Thus, it lays the basis for meaningfully investigating the
amount of context-sensitiveness supported by GIGs, but leaves this
investigation for further research
Generalized Stable Multivariate Distribution and Anisotropic Dilations
After having closely re-examined the notion of a L\'evy's stable vector, it
is shown that the notion of a stable multivariate distribution is more general
than previously defined. Indeed, a more intrinsic vector definition is obtained
with the help of non isotropic dilations and a related notion of generalized
scale. In this framework, the components of a stable vector may not only have
distinct Levy's stability indices 's, but the latter may depend on its
norm. Indeed, we demonstrate that the Levy's stability index of a vector rather
correspond to a linear application than to a scalar, and we show that the
former should satisfy a simple spectral property
Anomalous Scaling of Structure Functions and Dynamic Constraints on Turbulence Simulations
The connection between anomalous scaling of structure functions
(intermittency) and numerical methods for turbulence simulations is discussed.
It is argued that the computational work for direct numerical simulations (DNS)
of fully developed turbulence increases as , and not as
expected from Kolmogorov's theory, where is a large-scale Reynolds number.
Various relations for the moments of acceleration and velocity derivatives are
derived. An infinite set of exact constraints on dynamically consistent subgrid
models for Large Eddy Simulations (LES) is derived from the Navier-Stokes
equations, and some problems of principle associated with existing LES models
are highlighted.Comment: 18 page
Chelat- und nicht-chelat-kontrollierte reduktionen von β-amido-ketonen. Synthese nicht-racemischer 1,3-aminoalkohole mit pyrrolidinstruktur
ChemInform Abstract: HYBERBASIC MEDIA: SYNTHESIS OF α-CYANOCYCLANONES BY ANIONIC CYCLIZATION OF NITRILE AMIDES
ChemInform Abstract: ASYMMETRIC SYNTHESIS OF α-SUBSTITUTED KETONES AND ACIDS VIA CHIRAL N,N-SUBSTITUTED AMIDES
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