Presentation on theme: "Björn Pelzer (AGKI)LogAnswer1/11 LogAnswer Deduction-Based Question-Answering Deduction Meeting 2008 Hermann Helbig, Ingo GlöcknerUlrich Furbach, Björn."— Presentation transcript:
Björn Pelzer (AGKI)LogAnswer1/11 LogAnswer Deduction-Based Question-Answering Deduction Meeting 2008 Hermann Helbig, Ingo GlöcknerUlrich Furbach, Björn Pelzer
Björn Pelzer (AGKI)LogAnswer2/11 The Problem: Open-Domain Question-Answering: Example: "Who was the lead singer of Nirvana?" Kurt Cobain. A question-answering-system Advantages of QA compared to conventional search engines: time savings: answers instead of documents space savings: answers fit onto small displays finds textual answers to natural-language questions regarding arbitrary topics.
Björn Pelzer (AGKI)LogAnswer3/11 Specifically: Deduction-Based QA Existing QA-systems are (mostly) syntax-based: shallow linguistic methods like string comparisons database queries The peak of Mount Everest is 8848 metres above sea level. QA-system ? How tall is Mt. Everest? 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
Björn Pelzer (AGKI)LogAnswer4/11 Specifically: Deduction-Based QA LogAnswer uses a logic-based knowledge-representation. QA-system How tall is Mt. Everest? logical rules express semantics - "world knowledge" answers can be inferred using multiple sources 8848 metres The peak of Mount Everest is 8848 metres above sea level. (...) peak(P, M) dist(P, SL, D) height(M, D) (...)
Björn Pelzer (AGKI)LogAnswer5/11 LogAnswer - Overview natural language processing deduction robust linguistic methods lack of precision precise inferencing full FOL expressivity brittle NLP-components MultiNet knowledge-base – newspaper-corpus – Wikipedia – circa 2.5 million sentences E-KRHyper theorem prover The LogAnswer-project combines...
Björn Pelzer (AGKI)LogAnswer6/11 LogAnswer web interface answer question NL-question analysis LogAnswer - Prototype Architecture answer candidates answer composition logical answer facts background knowledge deduction results pre-analyzed text corpus logical query robust deduction control theorem prover E-KRHyper query + candidate
Björn Pelzer (AGKI)LogAnswer7/11 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
Björn Pelzer (AGKI)LogAnswer8/11 LogAnswer - Robust Deduction 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. 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) 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?)
Björn Pelzer (AGKI)LogAnswer9/11 LogAnswer - Robust Deduction 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) 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. 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.
Björn Pelzer (AGKI)LogAnswer10/11 answer: Tansania quality: 39% passage: 1893 begann die Arbeit am Kilimandscharo in Tansania. document: Leipziger_Missionswerk.239 Question: In welchem Land liegt der Kilimandscharo? (= What country is the Kilimanjaro located in?) 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 - Example
Björn Pelzer (AGKI)LogAnswer11/11 Thanks, see you at the poster! LogAnswer can be tested at www.loganswer.de
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