24,043 research outputs found
Machine Learning of Generic and User-Focused Summarization
A key problem in text summarization is finding a salience function which
determines what information in the source should be included in the summary.
This paper describes the use of machine learning on a training corpus of
documents and their abstracts to discover salience functions which describe
what combination of features is optimal for a given summarization task. The
method addresses both "generic" and user-focused summaries.Comment: In Proceedings of the Fifteenth National Conference on AI (AAAI-98),
p. 821-82
Query-Based Summarization using Rhetorical Structure Theory
Research on Question Answering is focused mainly on classifying the question type and finding
the answer. Presenting the answer in a way that suits the userās needs has received little
attention. This paper shows how existing question answering systemsāwhich aim at finding
precise answers to questionsācan be improved by exploiting summarization techniques to extract
more than just the answer from the document in which the answer resides. This is done
using a graph search algorithm which searches for relevant sentences in the discourse structure,
which is represented as a graph. The Rhetorical Structure Theory (RST) is used to create a
graph representation of a text document. The output is an extensive answer, which not only
answers the question, but also gives the user an opportunity to assess the accuracy of the answer
(is this what I am looking for?), and to find additional information that is related to the question,
and which may satisfy an information need. This has been implemented in a working multimodal
question answering system where it operates with two independently developed question
answering modules
Progress in AI Planning Research and Applications
Planning has made significant progress since its inception in the 1970s, in terms both of the efficiency and sophistication of its algorithms and representations and its potential for application to real problems. In this paper we sketch the foundations of planning as a sub-field of Artificial Intelligence and the history of its development over the past three decades. Then some of the recent achievements within the field are discussed and provided some experimental data demonstrating the progress that has been made in the application of general planners to realistic and complex problems. The paper concludes by identifying some of the open issues that remain as important challenges for future research in planning
U_A(1) Problems and Gluon Topology - Anomalous Symmetry in QCD
Many of the distinctive and subtle features of the dynamics in the
channel in QCD can be related to gluon topology, more precisely to the
topological susceptibility ,
where Q = {\a_s\over8\pi} {\rm tr} G_{\m\n} \tilde G^{\m\n} is the gluon
topological charge density. The link is the axial (ABJ) anomaly. In
this lecture, we describe the anomalous chiral Ward identities in a
functional formalism and show how two apparently unrelated ` problems'
-- the mass of the and the violation of the Ellis-Jaffe sum rule in
polarised deep-inelastic scattering -- can be explained in terms of the gluon
topological susceptibility. They are related through a extension of
the Goldberger-Treiman formula, which is derived here for QCD with both
massless and massive quarks.Comment: Lecture at 1998 Zuoz Summer School, `Hidden Symmetries and Higgs
Phenomena'. 22 pages, plain TeX, 2 ps or eps figure
Black Hole Formation and Classicalization in Ultra-Planckian 2 -> N Scattering
We establish a connection between the ultra-Planckian scattering amplitudes
in field and string theory and unitarization by black hole formation in these
scattering processes. Using as a guideline an explicit microscopic theory in
which the black hole represents a bound-state of many soft gravitons at the
quantum critical point, we were able to identify and compute a set of
perturbative amplitudes relevant for black hole formation. These are the
tree-level N-graviton scattering S-matrix elements in a kinematical regime
(called classicalization limit) where the two incoming ultra-Planckian
gravitons produce a large number N of soft gravitons. We compute these
amplitudes by using the Kawai-Lewellen-Tye relations, as well as scattering
equations and string theory techniques. We discover that this limit reveals the
key features of the microscopic corpuscular black hole N-portrait. In
particular, the perturbative suppression factor of a N-graviton final state,
derived from the amplitude, matches the non-perturbative black hole entropy
when N reaches the quantum criticality value, whereas final states with
different value of N are either suppressed or excluded by non-perturbative
corpuscular physics. Thus we identify the microscopic reason behind the black
hole dominance over other final states including non-black hole classical
object. In the parameterization of the classicalization limit the scattering
equations can be solved exactly allowing us to obtain closed expressions for
the high-energy limit of the open and closed superstring tree-level scattering
amplitudes for a generic number N of external legs. We demonstrate matching and
complementarity between the string theory and field theory in different large-s
and large-N regimes.Comment: 55 pages, 7 figures, LaTeX; v2: typos removed; final version to
appear in Nucl. Phys.
An Integrated Semantic Web Service Discovery and Composition Framework
In this paper we present a theoretical analysis of graph-based service
composition in terms of its dependency with service discovery. Driven by this
analysis we define a composition framework by means of integration with
fine-grained I/O service discovery that enables the generation of a graph-based
composition which contains the set of services that are semantically relevant
for an input-output request. The proposed framework also includes an optimal
composition search algorithm to extract the best composition from the graph
minimising the length and the number of services, and different graph
optimisations to improve the scalability of the system. A practical
implementation used for the empirical analysis is also provided. This analysis
proves the scalability and flexibility of our proposal and provides insights on
how integrated composition systems can be designed in order to achieve good
performance in real scenarios for the Web.Comment: Accepted to appear in IEEE Transactions on Services Computing 201
Irrationality of generic quotient varieties via Bogomolov multipliers
The Bogomolov multiplier of a group is the unramified Brauer group associated
to the quotient variety of a faithful representation of the group. This object
is an obstruction for the quotient variety to be stably rational. The purpose
of this paper is to study these multipliers associated to nilpotent pro-
groups by transporting them to their associated Lie algebras. Special focus is
set on the case of -adic Lie groups of nilpotency class , where we
analyse the moduli space. This is then applied to give information on
asymptotic behaviour of multipliers of finite images of such groups of exponent
. We show that with fixed and increasing , a positive proportion of
these groups of order have trivial multipliers. On the other hand, we
show that by fixing and increasing , log-generic groups of order
have non-trivial multipliers. Whence quotient varieties of faithful
representations of log-generic -groups are not stably rational. Applications
in non-commutative Iwasawa theory are developed.Comment: 34 pages; improved expositio
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