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Schlagwörter:
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Zusammenfassung:
The US presidential race, the re-election of President Hugo Chavez, and the
economic crisis in Greece and other European countries are some of the
controversial topics being played on the news everyday. To understand the
landscape of opinions on political controversies, it would be helpful to know
which politician or other stakeholder takes which position - support or
opposition - on specific aspects of these topics. The work described in this
thesis aims to automatically derive a map of the opinions-people network from
news and other Web documents. The focus is on acquiring opinions held by
various stakeholders on politically controversial topics. This opinions-people
network serves as a knowledge-base of opinions in the form of hopinion holderi
hopinioni htopici triples.
Our system to build this knowledge-base makes use of online news sources in
order to extract opinions from text snippets. These sources come with a set of
unique challenges. For example, processing text snippets involves not just
identifying the topic and the opinion, but also attributing that opinion to a
specific
opinion holder. This requires making use of deep parsing and analyzing the
parse tree. Moreover, in order to ensure uniformity, both the topic as well the
opinion holder should be mapped to canonical strings, and the topics should
also be organized into a hierarchy. Our system relies on two main components:
i) acquiring opinions which uses a combination of techniques to extract opinions
from online news sources, and ii) organizing topics which crawls and extracts
debates from online sources, and organizes these debates in a hierarchy of
political controversial topics. We present systematic evaluations of the
different components of our system, and show their high accuracies. We also
present some of the different kinds of applications that require political
analysis. We present some
application requires political analysis such as identifying flip-floppers,
political
bias, and dissenters. Such applications can make use of the knowledge-base of
opinions.
