Semantic Decomposition for Question Answering Introduction Decomposable questions

Semantic Decomposition for Question Answering 于佳婕

Introduction • Decomposable questions & Atomic questions • Decomposition form：sequences of two questions, later questions are built on top of the answers to earlier questions. • 6 decomposition classes, linked to different decomposition methods. • Decomposition methods are mostly based on the semantic representation of questions（Multi. Net formalism ）

Decomposition Classes • Temporal decomposition • Local decomposition • Coordinated situation decomposition • Meronymy decomposition • Description decomposition • Operational decomposition

Temporal Decomposition • A situation that is used as a temporal specification can be replaced by its date of occurrence. • E. g. Who was US president when Vietnam war ended ？ Who was US president when Vietnam war ended？ Wer war US-Pra sident, als der Vietnamkrieg endete? Who was US president in April 1975? Wer war US-Pra sident im April 1975? When did the Vietnam war end? Wann endete der Vietnamkrieg?

Local Decomposition • a local (or spatial) restriction can be replaced by the answer(s) to a subquestion about the exact location(s) fulfilling the restriction. • E. g. Which parties reign in countries that are in Northern Europe? =》（subquestion）Which countries are located in Northern Europe? =》（revised question with a list-valued answer）Which parties reign in Sweden, Norway, and Finland?

Coordinated Situation Decomposition • A question can contain several propositions also in the form of a conjunction of situations, often involving ellipsis. • E. g. Which football players played for Borussia Dortmund and Real Madrid? =》（subquestion）Which football players played for Borussia Dortmund? =》（revised question with a list-valued answer）Do …… played for Real Madrid?

Multisituation Decomposition • Involve 2 situations that are linked by a relation in the semantic network for the question. • Includes： • Temporal Decomposition • Local Decomposition • Coordinated situation Decomposition

Meronymy Decomposition • Meronymy decomposition tries to generate and exploit geographical knowledge on the fly (here: meronymy knowledge for geographical objects). • E. g. When did a hurricane hit Northern Germany? =》 （subquestion） Which regions/cities are in Northern Germany? =》（revised question with a list-valued answer）When did a hurricane hit Niedersachsen/Hamburg……?

Description Decomposition • Descriptions in question focus • E. g. Which Italian cities have an Olympic stadium? =》 （subquestion） Name Italian cities =》（revised question with a list-valued answer）Does Rome/Pisa…… have an Olympic stadium?

Operational Decomposition • Calculate an operation on the different answers of a subquestion • E. g. How many countries belonged to the EU in 1994? =》（subquestion）Name countries that belonged to the EU in 1994 =》 （revised question with a list-valued answer）count the countries in the answer of the subquestion • Sometimes can be answered directly（ The 12 EU member states…… ） • Operations：cardinality, maximum, minimum, mean average……

Evaluation

Some additional remarks • Sometimes decomposing questions can be dangerous • E. g. Multi-property Decomposition：a concept is modified by two or more properties. “Name a German communist politician. ” • A question can belong to zero or more decomposition classes • E. g. How many aristocrats were archbishops in Italy before the Western Schism? operational (How many), description (aristocrats), meronymy (in Italy), temporal (before the Western Schism). • A question can often be decomposed in several ways when it contains several propositions • Which planet orbits the sun once in every 12 years? • A：a) What orbits the sun once in every 12 years? b) Is �subanswer�a planet • B：a) Name planets! b) Does �subanswer�orbit the sun once in every 12 years?

A decomposition task • Which class does the question belong to • Where to split • How to adjust question type • How to integrate the subanswer(s) into the original question to form the revised question(s)