132,964 research outputs found
Facets and Typed Relations as Tools for Reasoning Processes in Information Retrieval
Faceted arrangement of entities and typed relations for representing
different associations between the entities are established tools in knowledge
representation. In this paper, a proposal is being discussed combining both
tools to draw inferences along relational paths. This approach may yield new
benefit for information retrieval processes, especially when modeled for
heterogeneous environments in the Semantic Web. Faceted arrangement can be used
as a se-lection tool for the semantic knowledge modeled within the knowledge
repre-sentation. Typed relations between the entities of different facets can
be used as restrictions for selecting them across the facets
Statistics of shared components in complex component systems
Many complex systems are modular. Such systems can be represented as
"component systems", i.e., sets of elementary components, such as LEGO bricks
in LEGO sets. The bricks found in a LEGO set reflect a target architecture,
which can be built following a set-specific list of instructions. In other
component systems, instead, the underlying functional design and constraints
are not obvious a priori, and their detection is often a challenge of both
scientific and practical importance, requiring a clear understanding of
component statistics. Importantly, some quantitative invariants appear to be
common to many component systems, most notably a common broad distribution of
component abundances, which often resembles the well-known Zipf's law. Such
"laws" affect in a general and non-trivial way the component statistics,
potentially hindering the identification of system-specific functional
constraints or generative processes. Here, we specifically focus on the
statistics of shared components, i.e., the distribution of the number of
components shared by different system-realizations, such as the common bricks
found in different LEGO sets. To account for the effects of component
heterogeneity, we consider a simple null model, which builds
system-realizations by random draws from a universe of possible components.
Under general assumptions on abundance heterogeneity, we provide analytical
estimates of component occurrence, which quantify exhaustively the statistics
of shared components. Surprisingly, this simple null model can positively
explain important features of empirical component-occurrence distributions
obtained from data on bacterial genomes, LEGO sets, and book chapters. Specific
architectural features and functional constraints can be detected from
occurrence patterns as deviations from these null predictions, as we show for
the illustrative case of the "core" genome in bacteria.Comment: 18 pages, 7 main figures, 7 supplementary figure
Requirements modelling and formal analysis using graph operations
The increasing complexity of enterprise systems requires a more advanced
analysis of the representation of services expected than is currently possible.
Consequently, the specification stage, which could be facilitated by formal
verification, becomes very important to the system life-cycle. This paper presents
a formal modelling approach, which may be used in order to better represent
the reality of the system and to verify the awaited or existing system’s properties,
taking into account the environmental characteristics. For that, we firstly propose
a formalization process based upon properties specification, and secondly we
use Conceptual Graphs operations to develop reasoning mechanisms of verifying
requirements statements. The graphic visualization of these reasoning enables us
to correctly capture the system specifications by making it easier to determine if
desired properties hold. It is applied to the field of Enterprise modelling
Fourier-based schemes with modified Green operator for computing the electrical response of heterogeneous media with accurate local fields
A modified Green operator is proposed as an improvement of Fourier-based
numerical schemes commonly used for computing the electrical or thermal
response of heterogeneous media. Contrary to other methods, the number of
iterations necessary to achieve convergence tends to a finite value when the
contrast of properties between the phases becomes infinite. Furthermore, it is
shown that the method produces much more accurate local fields inside
highly-conducting and quasi-insulating phases, as well as in the vicinity of
the phases interfaces. These good properties stem from the discretization of
Green's function, which is consistent with the pixel grid while retaining the
local nature of the operator that acts on the polarization field. Finally, a
fast implementation of the "direct scheme" of Moulinec et al. (1994) that
allows for parcimonious memory use is proposed.Comment: v2: `postprint' document (a few remaining typos in the published
version herein corrected in red; results unchanged
- …