Centering: A Framework for Modeling the Local Coherence of Discourse

2 Phenomena to be explained

1. Two versions of “John went to his favorite music store to buy a piano…” say the same thing. Why is one more coherent?

   (1)	(2)
   John went to his favorite music store to buy a piano.	John went to his favorite music store to buy a piano.
   He had frequented the store for many years.	It was a store John had frequented for many years.
   He was excited that he could finally buy a piano.	He was excited that he could finally buy a piano.
   He arrived just as the store was closing for the day.	It was closing just as John arrived.

   Both convey the same content, but (1) stays centered on John while (2) flips back and forth between John and the store.
   • Grosz et al., 1995, Centering (Computational Linguistics), §2
2. What is “inference load”?
   The resources a hearer needs to extract information from a discourse because of the particular linguistic forms chosen. Centering conjectures that discourses with the same propositional content but higher inference load are perceived as less coherent.
   • Grosz et al., 1995, Centering (Computational Linguistics), §2
3. What goes wrong in “Terry … He wanted Tony to join him … He called him at 6 AM. He was sick and furious at being woken up so early.”?
   Terry has been the center, so “he” is first taken as Terry; only at “sick” does it become clear that Tony is meant, forcing the hearer to backtrack. Using “Tony” instead of “he” avoids the misdirection.
   • Grosz et al., 1995, Centering (Computational Linguistics), §2