4. The acquisition of Alaska by the United
module, all named entities of the expected answer
States of America from Russia in 1867 is
known as “Seward’s Folly”.
types are treated as answer candidates. For ques-
tions with an unknown answer type, all NPs in
The remaining three sentences introduce vari-
the candidate sentence are considered. Then those
ous forms of syntactic and semantic transforma-
paths in the answer sentence that are connected
tions. In order to capture a wide range of possible
to an answer candidate are compared against the
ways on how answer sentences can be formulated,
corresponding paths in the question, in a similar
in our model a candidate sentence is not evalu-
fashion as in (Cui et al., 2005). The candidate
ated according to its similarity with the question.
whose paths show the highest matching score is
Instead, its similarity to known answer sentences
selected. (Shen and Klakow, 2006) also describe
(which were presented to the system during train-
a method that is primarily based on similarity
ing) is evaluated. This allows to us to capture a
scores between dependency relation pairs. How-
much wider range of syntactic and semantic trans-
ever, their algorithm computes the similarity of
formations.
paths between key phrases, not between words.
Furthermore, it takes relations in a path not as in-
3 Overview of the Algorithm
dependent from each other, but acknowledges that
they form a sequence, by comparing two paths
Our algorithm uses input data containing pairs of
with the help of an adaptation of the Dynamic
the following:
Time Warping algorithm (Rabiner et al., 1991).
(Molla, 2006) presents an approach for the ac-
NLQs/Questions NLQs that describe the users’
quisition of question answering rules by apply-
information need. For the experiments car-
ing graph manipulation methods. Questions are
ried out in this paper we use questions from
represented as dependency graphs, which are ex-
the TREC QA track 2002-2006.
tended with information from answer sentences.
Relevant textual content This is a piece of text
These combined graphs can then be used to iden-
that is relevant to the user query in that it
tify answers. Finally, in (Wang et al., 2007), a
contains the information the user is search-
quasi-synchronous grammar (Smith and Eisner,
ing for. In this paper, we use sentences ex-
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