4,273,769 research outputs found
Information sources: Overview
In this chapter, some of the major information sources for information related to organic farming are presented. The International Trade Centre (ITC) has recently considerably expanded its information and market access services. These are presented in detail
Reductions of Hidden Information Sources
In all but special circumstances, measurements of time-dependent processes
reflect internal structures and correlations only indirectly. Building
predictive models of such hidden information sources requires discovering, in
some way, the internal states and mechanisms. Unfortunately, there are often
many possible models that are observationally equivalent. Here we show that the
situation is not as arbitrary as one would think. We show that generators of
hidden stochastic processes can be reduced to a minimal form and compare this
reduced representation to that provided by computational mechanics--the
epsilon-machine. On the way to developing deeper, measure-theoretic foundations
for the latter, we introduce a new two-step reduction process. The first step
(internal-event reduction) produces the smallest observationally equivalent
sigma-algebra and the second (internal-state reduction) removes sigma-algebra
components that are redundant for optimal prediction. For several classes of
stochastic dynamical systems these reductions produce representations that are
equivalent to epsilon-machines.Comment: 12 pages, 4 figures; 30 citations; Updates at
http://www.santafe.edu/~cm
Network Information Flow with Correlated Sources
In this paper, we consider a network communications problem in which multiple
correlated sources must be delivered to a single data collector node, over a
network of noisy independent point-to-point channels. We prove that perfect
reconstruction of all the sources at the sink is possible if and only if, for
all partitions of the network nodes into two subsets S and S^c such that the
sink is always in S^c, we have that H(U_S|U_{S^c}) < \sum_{i\in S,j\in S^c}
C_{ij}. Our main finding is that in this setup a general source/channel
separation theorem holds, and that Shannon information behaves as a classical
network flow, identical in nature to the flow of water in pipes. At first
glance, it might seem surprising that separation holds in a fairly general
network situation like the one we study. A closer look, however, reveals that
the reason for this is that our model allows only for independent
point-to-point channels between pairs of nodes, and not multiple-access and/or
broadcast channels, for which separation is well known not to hold. This
``information as flow'' view provides an algorithmic interpretation for our
results, among which perhaps the most important one is the optimality of
implementing codes using a layered protocol stack.Comment: Final version, to appear in the IEEE Transactions on Information
Theory -- contains (very) minor changes based on the last round of review
Active Ontology: An Information Integration Approach for Dynamic Information Sources
In this paper we describe an ontology-based information integration approach that is suitable for highly dynamic distributed information sources, such as those available in Grid systems. The main challenges addressed are: 1) information changes frequently and information requests have to be answered quickly in order to provide up-to-date information; and 2) the most suitable information sources have to be selected from a set of different distributed ones that can provide the information needed. To deal with the first challenge we use an information cache that works with an update-on-demand policy. To deal with the second we add an information source selection step to the usual architecture used for ontology-based information integration. To illustrate our approach, we have developed an information service that aggregates metadata available in hundreds of information services of the EGEE Grid infrastructure
Archaeological fragments and other sources of information
Although the medium I have chosen to discuss, sculpture, is an artistic one and involves
by its own nature strong elements of aesthetics and iconography, I shall deal with it also
from the archaeological perspective. This distinction between these two disciplines was
brought to the fore in my mind by a recent article in an Italian archaeological magazine
which commemorated a man who rightly deserves to be considered the founder of ancient
Classical art history, namely, Johann Joachim Winkelmann (1717-1767). Winkelmann set
down and published the first history of Greco-Roman art in 1764. The authors of the article
declared him to be the first archaeologist and to have introduced the archaeological method
in the study of ancient art. At first I found this attribution questionable since it is nowhere
recorded that he was ever involved in archaeological field work, but then I realized that
this attitude is, or was, quite standard in continental academic circles, as opposed to AngloSaxon
ones. I should have known better since I had my professional training in both of them,
having studied in the lstituto di Archeologia e Storia dell'Arte Antica of the University of
Palermo and at the Institute of Archaeology of the University of London.peer-reviewe
Directory of aerospace safety specialized information sources
Directory aids safety specialists in locating information sources and individual experts in engineering-related fields. Lists 170 organizations and approximately 300 individuals who can provide safety-related technical information in form of documentation, data, and consulting expertise. Information on hazard and failure cause identification, accident analysis, and materials characteristics are covered
Combining information from independent sources through confidence distributions
This paper develops new methodology, together with related theories, for
combining information from independent studies through confidence
distributions. A formal definition of a confidence distribution and its
asymptotic counterpart (i.e., asymptotic confidence distribution) are given and
illustrated in the context of combining information. Two general combination
methods are developed: the first along the lines of combining p-values, with
some notable differences in regard to optimality of Bahadur type efficiency;
the second by multiplying and normalizing confidence densities. The latter
approach is inspired by the common approach of multiplying likelihood functions
for combining parametric information. The paper also develops adaptive
combining methods, with supporting asymptotic theory which should be of
practical interest. The key point of the adaptive development is that the
methods attempt to combine only the correct information, downweighting or
excluding studies containing little or wrong information about the true
parameter of interest. The combination methodologies are illustrated in
simulated and real data examples with a variety of applications.Comment: Published at http://dx.doi.org/10.1214/009053604000001084 in the
Annals of Statistics (http://www.imstat.org/aos/) by the Institute of
Mathematical Statistics (http://www.imstat.org
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