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Binding Theory in LTAG

Binding Theory in LTAG. Lucas Champollion University of Pennsylvania champoll@ling.upenn.edu. Overview. Binding Theory (BT) and its local domains Previous work: Condition A This proposal: Conditions A, B, C Discussion. Binding theory: A reminder.

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Binding Theory in LTAG

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  1. Binding Theory in LTAG Lucas Champollion University of Pennsylvania champoll@ling.upenn.edu TAG+9

  2. Overview • Binding Theory (BT) and its local domains • Previous work: Condition A • This proposal: Conditions A, B, C • Discussion TAG+9

  3. Binding theory: A reminder • Condition A: reflexives must be locally bound • Johnj thinks [ Billb likes himself*j / b / *[other]] • Condition B: pronouns must be locally free • Johnj thinks [ Billb likes himj / *b / [other] ] • Condition C: full noun phrases must be free • *[ Johnj likes Johnj ] • *Johnj thinks [ Mary likes Johnj ] TAG+9

  4. Binding theory in LTAG • LTAG’s local domain = the verbal elementary tree and its arguments • (but not its adjuncts) • Insight from previous work: • LTAG and BT have similar local domains • This presentation’s central point: • Too many mismatches between local domains • We can’t reuse LTAG’s local domain for binding! TAG+9

  5. Previous work reused LTAG’s local domain S NP VP V S* John thinks S NP VP V NP he loves himself Condition A TAG+9

  6. Previous work reused LTAG’s local domain S NP VP V S* John thinks S NP VP V NP he loves himself Condition A TAG+9

  7. Previous work reused LTAG’s local domain S NP VP V S* John thinks S NP VP V NP he loves himself Condition A TAG+9

  8. Previous work reused LTAG’s local domain S NP VP V S* John thinks S NP VP V NP he loves him Condition B TAG+9

  9. NP John NPi himself Ryant and Scheffler (2006) S • Only Condition A • MCTAG set with a degenerate NP tree • Tree-local MCTAG with flexible composition makes sure that antecedent and reflexive substitute into the same tree NP VP V NP loves { } NP*i TAG+9

  10. NP John NPi himself Kallmeyer and Romero (2007) S • Only Condition A • MCTAG set with a degenerate VP tree • Tree-local MCTAG with flexible composition makes sure that antecedent and reflexive substitute into the same tree NP VP V NP loves { } VP*i (some features omitted) TAG+9

  11. Kallmeyer and Romero’s claim “Tree-local MCTAG display exactly the extended domain of locality needed to account for the locality of anaphora binding in a natural way.” -- Kallmeyer and Romero (2007) TAG+9

  12. A counterexample S VP NP VP VP* PP V NP John P NP imagined Bill opposite himself • Cannot be handled by Kallmeyer and Romero (2007) • except by flexible composition (which they try to avoid) TAG+9

  13. ECM: another mismatch of localities S NP VP V S* John S expects NP VP him V NP to love Bill • Can be handled with an extra feature • No lexical ambiguity needed (unlike R&S 2006) TAG+9

  14. S S NP NP VP VP NP NP V V NP NP NP NP John John found found NP* NP* N’ N’ Det Det NP NP NP NP ’s ’s NP NP PP PP N N Bill Bill P P picture picture NP* NP* of of NP NP him himself Mismatches within Binding Theory B A Judgments tested experimentally (Keller and Asudeh ‘01; Runner ‘03) TAG+9

  15. Mismatches within Binding Theory VP A S VP* PP VP NP NP P NP V John near himself a snake saw VP B S VP* PP VP NP NP P John NP V near him saw a snake TAG+9

  16. How to encode the other conditions? • Condition A roughly corresponds to tree-locality • Condition B = “enforced non-locality”? • Condition C = ??? • Need to propagate an unbounded number of potential antecedents TAG+9

  17. This account in a nutshell • Every NP receives three items from its environment: • a list “A” of local potential antecedents • a list “B” of local potential antecedents • a list “C” of nonlocal potential antecedents • Every NP supplies its own individual variable to its environment • The rest of the grammar is responsible for providing the correct lists to the NP substitution slots TAG+9

  18. Technical innovation: List-valued features TAG+9

  19. Elementary tree for “himself”(Condition A, simplified) • “A reflexive must be locally bound.” TAG+9

  20. Elementary tree for “he”(Condition B) • “A pronoun must be locally free.” TAG+9

  21. Elementary tree for “John” (Condition C) • “A full noun phrase must be free.” TAG+9

  22. Sample derivation TAG+9

  23. Sample derivation TAG+9

  24. Sample derivation TAG+9

  25. Sample derivation TAG+9

  26. Condition C: the default case Before... TAG+9

  27. Condition C: the default case ...and after unification of top/bottom features TAG+9

  28. Condition C across clauses Before putting the trees together... TAG+9

  29. Condition C across clauses The higher tree passes its subject down, then... TAG+9

  30. Condition C across clauses ...unification at the root node propagates the empty list TAG+9

  31. Improvements over previous accounts... TAG+9

  32. Binding into adjuncts • Just propagate everything! TAG+9

  33. Mismatches between domains easily encoded • Non-complementary binding conditions easily handled with separate A and B list features • No ad hoc trees needed for picture NPs (unlike K&R ‘07) TAG+9

  34. C-command violations easily encoded • e.g. extraposition: “Himselfi, hei likes.” • No need for separate lexical entry • Just extrapose subject NP along with its feature structure (Himself) (he) TAG+9

  35. Improvements at a glance • All conditions are implemented • Higher empirical accuracy • No lexical ambiguity • No flexible composition (K&R 2007) • No syntactically unmotivated degenerate trees (Kallmeyer and Romero, 2008) • Better integration with anaphora resolution (Branco, 2002) • No explicit representation of c-command TAG+9

  36. Issues / Future work • Unknown complexity of list-valued features • Just a decoration on the trees though -- they do not rule out any sentences • Lack of predictive power • How do we constrain possible feature values? • Metagrammar? • Does TAG offer any insights into BT at all? TAG+9

  37. Thank you. Lucas Champollion University of Pennsylvania champoll@ling.upenn.edu TAG+9

  38. Previous accounts do not interface well with anaphora resolution modules • Previous accounts: parser delivers a forest of indexed trees • Johni introduced Billk to himselfivs. Johni introduced Billk to himselfk • Problem: Anaphora resolution modules are not prepared to compare entire trees (Branco, 2002) • Our solution outputs a compact set of constraints • Following Branco (2002) TAG+9

  39. S NP VP NP V NP John found NP NP* N’ NP NP NP Det PP N ’s Bill P picture NP* of NP himself The grammar of picture NPs TAG+9

  40. S NP VP NP V NP John found NP NP* N’ NP NP NP Det PP N ’s Bill P picture NP* of NP himself Missing link problem TAG+9

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