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Deduction Meeting 2008. Hermann Helbig, Ingo Glöckner. Ulrich Furbach, Björn Pelzer. LogAnswer Deduction-Based Question-Answering. The Problem: Open-Domain Question-Answering:. A question-answering-system. finds textual answers to natural-language questions regarding arbitrary topics.

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Deduction Meeting 2008

Hermann Helbig, Ingo Glöckner

Ulrich Furbach, Björn Pelzer

LogAnswerDeduction-Based Question-Answering

LogAnswer


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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

LogAnswer


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Specifically: Deduction-Based QA

The peak of Mount Everest is 8848 metres above sea level.

QA-system

How tall is

Mt. Everest?

?

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

LogAnswer


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Specifically: Deduction-Based QA

The peak of Mount Everest is 8848 metres above sea level.

QA-system

How tall is

Mt. Everest?

(...)

peak(P, M) 

dist(P, SL, D)

 height(M, D)

(...)

8848 metres

LogAnswer uses a logic-based knowledge-representation.

  • logical rules express semantics - "world knowledge"

  • answers can be inferred using multiple sources

LogAnswer


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LogAnswer - Overview

The LogAnswer-project combines...

LogAnswer


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LogAnswer - Prototype Architecture

LogAnswer web interface

answer

question

answer composition

NL-question analysis

robust deduction control

logical answer facts

logical query

query + candidate

deduction results

theorem prover E-KRHyper

answer candidates

pre-analyzed text corpus

background knowledge

LogAnswer


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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

LogAnswer


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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.

LogAnswer


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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.

LogAnswer


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LogAnswer - Example

Question:In welchem Land liegt der Kilimandscharo?

(= What country is the Kilimanjaro located in?)

answer:Tansaniaquality: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

LogAnswer


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LogAnswer can be tested at

www.loganswer.de

Thanks, see you at the poster!

LogAnswer


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