1. Slide 1 of 13 Increasing the coverage of answer extraction by applying anaphora resolution Increasing the coverage of answer extraction by applying anaphora resolution IS-LTC October 10 2006 Jori Mur Humanities Computing University of Groningen

2. Slide 2 of 13 Increasing the coverage of answer extraction by applying anaphora resolution Outline Background Question Answering (QA) Off-line answer extraction Anaphora resolution for answer extraction Anaphora resolution technique for definite nouns Anaphora resolution technique for pronouns Experiment and Results Conclusion

3. Slide 3 of 13 Increasing the coverage of answer extraction by applying anaphora resolution Question Anwering (QA) Task: Find an answer in a text collection to a question posed in a natural language. Question: How old is John McEnroe? Answer: 35 years Question: When was Hillary Clinton born? Answer: October 26 1947

4. Slide 4 of 13 Increasing the coverage of answer extraction by applying anaphora resolution Off-line answer extraction Use dependency parser to parse the corpus Define dependency patterns [Location Name] has [Number] inhabitants Match dependency relations of sentence from text with dependency pattern Extract and save facts

5. Slide 5 of 13 Increasing the coverage of answer extraction by applying anaphora resolution Problem Text: McEnroe was injured on his right knee. [...] The problems with his knee kept bothering the 35-year old American for two weeks.

6. Slide 6 of 13 Increasing the coverage of answer extraction by applying anaphora resolution Anaphora resolution for definite nouns Modify patterns to match definite nouns [Definite noun] has [Number] inhabitants Create instance list using predicate and apposition relation Select first preceding name, check if it occurs together with the noun at the instance list Fall back: select first preceding name

7. Slide 7 of 13 Increasing the coverage of answer extraction by applying anaphora resolution Experiment 12 question types Age Date of Birth Location of Birth Capital Date of Death Location of Death Manner/Cause of Death Age of Death Founded Function Inhabitants Winner

8. Slide 8 of 13 Increasing the coverage of answer extraction by applying anaphora resolution Experiment Clef corpus for Dutch: Two newspapers (Algemeen Dagblad and NRC Handelsblad) 1994 and 1995 Simple predefined dependency patterns and patterns based on anaphora resolution 200 Dutch Questions of Clef-2005 QA system: Joost

9. Slide 9 of 13 Increasing the coverage of answer extraction by applying anaphora resolution Results for extraction Around 10,900 fact-types extra Basic patternsAnaphora patterns Fact-tokens93497 (86%)+51644 (34%) Fact-types64627 (75%)+39208 (28%)

10. Slide 10 of 13 Increasing the coverage of answer extraction by applying anaphora resolution Results for QA 200 questions from Clef-2005 data-set Basic patternsAnaphora patterns Total103/200 (52%)105/200 (53%) 12 types26/40 (65%)28/40 (70%)

11. Slide 11 of 13 Increasing the coverage of answer extraction by applying anaphora resolution Discussion of Results Hypothesis 1: Precision should be increased. Hypothesis 2: Selection of types was limited. Hypothesis 3: Answers to questions occur in one sentence

12. Slide 12 of 13 Increasing the coverage of answer extraction by applying anaphora resolution Answer in one sentence Question 107: Who was the pilot of the mission that repaired the astronomic satelite, the Hubble Space Telescope? Text AD19940719: Bowersox was the pilot of the mission that repaired the astronomic satelite, the Hubble Space Telescope.

13. Slide 13 of 13 Increasing the coverage of answer extraction by applying anaphora resolution Conclusion One way to improve the coverage of answer extraction is anaphora resolution Although precision drops it doesn’t hurt the performance of QA. Result even improved. It should be investigated what happens if the domain of question types on which anaphora resolution is applied is broadened It should be investigated what happens if the questions are really independent of the corpus

14. Slide 14 of 13 Increasing the coverage of answer extraction by applying anaphora resolution Questions?

15. Slide 15 of 13 Increasing the coverage of answer extraction by applying anaphora resolution Anaphora resolution for pronouns Modify patterns to match pronouns [Pronoun] has [Number] inhabitants Create list of boys and girls names (baby names site at the internet) Select first preceding name, check if it does not occur on the list of the opposite sexe of the pronoun Fall back: select first preceding name

16. Slide 16 of 13 Increasing the coverage of answer extraction by applying anaphora resolution Example Text: NH19941209 35-year old McEnroe... Question: How old is McEnroe ? Answer: 35 NameAgeId McEnroe35NH19941209