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Governing Category and Coreference

Governing Category and Coreference. Dekang Lin Department of Computing Science University of Alberta. Constraints on Coreference Relationships. John hurt himself *Miss Marple hurt himself John likes him John said Peter likes him She likes Susan She said Jan likes Susan. C-command.

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Governing Category and Coreference

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  1. Governing Category and Coreference Dekang Lin Department of Computing Science University of Alberta

  2. Constraints on Coreference Relationships • John hurt himself • *Miss Marple hurt himself • John likes him • John said Peter likes him • She likes Susan • She said Jan likes Susan

  3. C-command • C-command is a relationship between two nodes in a parse tree • c-commands if 1.  does not dominate  2. the parent of  dominates  • dominates if  is an ancestor of  in the parse tree NP Det N’ a N PP forecast P NP of AP N returns A future

  4. Binding • A noun phrase  is bound to another noun phrase  if •  and  are co-indexed (refer to the same entity) •  c-commands . • Examples • John hurt himself • John likes him • John said Peter likes him • She likes Susan • She said Jan likes Susan

  5. Classification of NPs • NPs can be classified into the following categories according to their binding property: • R-Expressions: Mary, the policeman, the company • Pronominals: he, she, you, her, his, ... • Reciprocals and reflexives: each other, himself, herself, ... • Chomsky82: -anaphor +anaphor -pronominal R-expressions Refl/Recp +pronominal Pronominals PRO

  6. Binding Theory • Tentative Definition: The local domain of phrase is the smallest clause that contains the phrase. • Principle A: A NP with [+anaphor] must be bound within its local domain. • Principle B: A NP with [+pronominal] must not be bound within its local domain. • Principle C: A NP with [-anaphor -pronominal] must not be bound.

  7. Examples • John hurt himself • John likes him • John said Peter likes him • She likes Susan • She said Jan likes Susan • *John thinks that himself is the best candidate • John considered himself to be the best candidate • John said that pictures of himself were on sale. • Peter read John’s story about himself/him. • *John wanted Mary to take a picture of himself.

  8. Government • Government is a relationship between two nodes in a parse tree. •  governs  if • 1.  is the head of a phrase and a potential governor • 2. A phrase headed by  dominates  • 3. There does not exist a g such at g governs  and  governs g • Potential governors • All lexical categories: N, V, A, P • Head of finite clauses

  9. Binding Theory (Revised) • The governing category of  is the minimal phrase that contains , the governor of , and a subject (a NP at spec of an IP or a NP) that c-commands the governor. • Binding Theory • Principle A: A NP with [+anaphor] must be bound within its governing category. • Principle B: A NP with [+pronominal] must not be bound within its governing category. • Principle C: A NP with [-anaphor -pronominal] must not be bound.

  10. Example 1 • John likes himself

  11. Example 2 • Mary likes John’s picture of himself

  12. Example 3 • *John wanted Mary to take a picture of himself

  13. Example 4 • John considers himself to be the best

  14. Example 5 • John said that pictures of himself were on sale

  15. Example 6 • *Mary believes herself can afford the car

  16. Binding and PRO • PRO is treated like lexical NPs • John persuaded Maryi PROi to defend herself/*himself • Johni promised Mary PROi to defend himself/*herself

  17. Problem Cases • They knew/found that each other’s photos were on sale • Mary believes it is possible for herself to win • Jill knew that nothing could obliterate the memory of those photographs of herself [Napoli93] • Ralph considers Mary inferior to himself [Napoli93, p.519] • ?Ralph considers John inferior to himself

  18. Local Domain (Revisted Again) • The Local Domain of  is the minimal phrase that contains  , its governor, and a subject (a NP at spec of an IP or a NP) that c-commands the governor and is accessible to .

  19. Non-referential NPs • Some NPs, such as nothing, there, it (expletive), are not accessible to anything.

  20. Each Other’s • “Each other’s” is not accessible to “each other’s”

  21. A Singular Nouns is not Accessible to “Each Other” • Pollard&Sag 94, p.245 • John and Mary know that the journal had rejected each other’s papers • Why are John and Mary letting the honey drip on each other’s feet [Chomsky 1973: 261] • John suggested that tiny gilt-framed portraits of each other would make ideal gifts for the twins • The agreement that Iran and Iraq reached guaranteed each other’s trading rights in the disputed waters until the year 2010

  22. Inaccessibility between Argumentsof a Predicate • If two arguments of a predicate are known to be distinct a priori, they are not accessible to each other. • Ralph considers Mary inferior to himself [Napoli93, p.519] • *Ralph considers Mary fond of himself [Napoli93, p.519]

  23. Accessibility • A is inaccessible to B if, disregarding agreement features, A could not possibly bind B. • Otherwise, A is accessible to B

  24. Exceptions to Principle B • Example • Jill took her brother with her to the market [Napoli93,513] • The use of “her” instead of “herself” may be explained by Full Interpretation • “X took Y with Z” implies Z=X. • the only purpose to use an anaphor as Z is to indicate Z=X

  25. Exceptions to Principle C • ABC applauded the new contract, which gave the network more flexibility. • The company said it plans to use the sale proceeds to invest in business opportunities more closely identified with the company’s “refocused direction.”

  26. Anaphors without Governing Category • Not all anaphors have governing categories: • A letter from Mary about herself was in the mail [Kuno93, p.138] • Those nude pictures of himself ruined John’s career. [Napoli93, p550] • RevisedPrinciple A: • If an anaphor has a governing category, it must be bound within its governing category. • If an anaphor has no governing category, it must be co-indexed with the most accessible NP in the context.

  27. Examples of Anaphor without GC • The picture of himselfi in Newsweek bothered Johni • *The picture of himselfi in Newsweek bothered John’si father • The picture of himselfi in Newsweek dominated John’si thoughts • The picture of himselfi in Newsweek shattered the piece of mind that Johni had spent the last six months trying to restore.

  28. Conclusion • We proposed a definition of Governing Category that is simpler and has better empirical coverage than Chomsky’s earlier definition.

  29. Unresolved Problems • John made sure it was clear to Mary that the picture of himself was already sold • Mary made sure it was clear to John that the picture of himself was already sold • Bill suspected the silence meant that a picture of himself would soon be on the post office wall [Pollard&Sag94, p.268]

  30. Problems with C-command • Pollard&Sag94 pointed out the following problems • Mary talked to John about himself • *Mary talked to himi about Johni • Possible solution • redefine c-command so that prepositions do not block c-command • introduce linear order requirement in c-command

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