LogAnswer Deduction-Based Question-Answering

1. Deduction Meeting 2008 Hermann Helbig, Ingo Glöckner Ulrich Furbach, Björn Pelzer LogAnswerDeduction-Based Question-Answering LogAnswer

2. 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

3. 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

4. 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

5. LogAnswer - Overview The LogAnswer-project combines... LogAnswer

6. 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

7. 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

8. 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

9. 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

10. 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

11. LogAnswer can be tested at www.loganswer.de Thanks, see you at the poster! LogAnswer