LogAnswer DeductionBased QuestionAnswering

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LogAnswerDeduction-Based Question-Answering
Deduction Meeting 2008
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The Problem Open-Domain Question-Answering
A question-answering-system

• finds textual answers
• to natural-language questions
• regarding arbitrary topics.

• Example
• "Who was the lead singer of Nirvana?"
• ? Kurt Cobain.

• Advantages of QA compared to conventional search
  engines
• time savings answers instead of documents
• space savings answers fit onto small displays

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Specifically Deduction-Based QA

• Existing QA-systems are (mostly) syntax-based
• shallow linguistic methods like string
  comparisons
• database queries

Problems

• no semantics available to the system
• no matching strings or strings too far apart ? no
  answer
• can be made robust, but answer quality degrades

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Specifically Deduction-Based QA

• LogAnswer uses a logic-based knowledge-representat
  ion.

• logical rules express semantics - "world
  knowledge"
• answers can be inferred using multiple sources

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LogAnswer - Overview
The LogAnswer-project combines...
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LogAnswer - Prototype Architecture
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LogAnswer - Prototype Architecture - Theorem
Prover

• E-KRHyper
• Knowledge Representation Hypertableau theorem
  prover for full first-order logic with Equality
• support for TPTP-input
• operates as reasoning server
• general background knowledge is entered once
• query-specific clauses are entered and retracted
  as needed

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LogAnswer - Robust Deduction
A query is represented as a conjunction of
literals.
Wie viele Menschen starben beim Untergang der
Estonia? ( How many people died in the sinking
of the Estonia?)
sub(X1, estonia.1.1) ? attch(X1, X2) ? subs(X2,
untergang.1.1) ? subs(X3, sterben.1.1) ? circ(X3,
X2) ? aff(X3, ANSWER) ? pred(ANSWER, mensch.1.1)
Problem Logic is too precise. The query is too
demanding for a knowledge base derived from
imperfect textual sources ? The answer is there,
but we don't find it.
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LogAnswer - Robust Deduction

• Solution Query Relaxation
• The prover informs LogAnswer how far the proof
  has progressed and for which query literals it
  fails.
• LogAnswer selects the most successful partial
  proof, drops the failed literal from the query
  and restarts the prover.

sub(X1, estonia.1.1) ? attch(X1, X2) ? subs(X2,
untergang.1.1) ? subs(X3, sterben.1.1) ? circ(X3,
X2) ? aff(X3, ANSWER) ? pred(ANSWER, mensch.1.1)
? ANSWER 852 (2 relaxations)

• Answer candidates are ranked according to the
  number of relaxations required for a proof (and
  other criteria).

• The best answers are selected and returned to
  the user.

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LogAnswer - Example
Question In welchem Land liegt der
Kilimandscharo? ( What country is the
Kilimanjaro located in?)
answer Tansania quality 39 passage 1893
begann die Arbeit am Kilimandscharo in Tansania .
document Leipziger_Missionswerk.239
answer Arusha quality 14 passage Er liegt
im Nordosten nördlich von Arusha und nahe der
kenianischen Grenze zwischen dem Mount Meru und
dem Kilimandscharo und ist über den
internationalen Flughafen Kilimanjaro bei Arusha
erreichbar . document Arusha-Nationalpark.90
answer Afrika quality 13 passage Schnee auf
dem Kilimandscharo ) , 1936 - Kurzgeschichte aus
Afrika To have and have not ( dt . document
Ernest_Hemingway.4638
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LogAnswer can be tested at www.loganswer.de
Thanks, see you at the poster!