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组合范畴语法

组合范畴语法. 孙薇薇 @ 计算机科学技术研究所 @ 北京大学. Why I teach this course?. 我上电影学院时，每周三都有两部最新的国产电影可以看，没有一部跟中国人真实的感受和处境有任何关系。我决定自己干，把我认为被银幕遮蔽掉的生活呈现出来，这是我最初做电影的动力。 —— 贾樟柯. Why I teach this course?. 请大家积极参与课程评估！. Motivation for (C)CG.

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组合范畴语法

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  1. 组合范畴语法 孙薇薇@ 计算机科学技术研究所@北京大学

  2. Why I teach this course? 我上电影学院时，每周三都有两部最新的国产电影可以看，没有一部跟中国人真实的感受和处境有任何关系。我决定自己干，把我认为被银幕遮蔽掉的生活呈现出来，这是我最初做电影的动力。 ——贾樟柯

  3. Why I teach this course? • 请大家积极参与课程评估！

  4. Motivation for (C)CG • Only a “minimal” extension to CFGs → formalism is also well-understood from a logical standpoint • Transparent interface to (compositional) semantics • Cross-linguistic generalizations can be made easily • the same set of rules always apply • Flexible constituency

  5. Combinatory Categorial Grammar • Categories: specify subcat lists of words/constituents. • Combinatory rules: specify how constituents can combine. • The lexicon: specifies which categories a word can have. • Derivations: spell out process of combining constituents.

  6. CCG categories • Simple categories:NP, S, PP • Complex categories: functions which return a result when combined with an argument: VP or intransitive verb: S\NPTransitive verb: (S\NP)/NPAdverb: (S\NP)\(S\NP)PPs: ((S\NP)\(S\NP))/NP(NP\NP)/NP • Every category has a semantic interpretation

  7. The combinatory rules • Function application: x.f(x) a  f(a) X/YY X (>) Y X\Y  X (<) • Function composition: x.f(x) y.g(y)  x.f(g(x)) X/Y Y/Z X/Z(>B) Y\Z X\Y  X/Z(<B) X/YY\Z X\Z(>Bx) Y/Z X\Y  X/Z(<Bx) • Type-raising: a f.f(a) X T/(T\X) (>T) X T\(T/X) (<T)

  8. Function application • Combines a function with its argument to yield aresult:(S\NP)/NP NP -> S\NPeats tapas eats tapasNPS\NP -> SJohn eats tapas John eats tapas • Used in all variants of categorial grammar

  9. A (C)CG derivation

  10. Type-raising and function composition • Type-raising: turns an argument into a function.Corresponds to case: NP -> S/(S\NP) (nominative)NP -> (S\NP)/((S\NP)/NP) (accusative) • Function composition: composes two functions (complex categories)(S\NP)/PP PP/NP -> (S\NP)/NPS/(S\NP) (S\NP)/NP -> S/NP

  11. Type-raising and Composition • Wh-movement: • Right-node raising:

  12. Another CCG derivation

  13. CCG: semantics • Every syntactic categoryand rule has a semantic counterpart:

  14. The CCG lexicon • Pairs words with their syntactic categories(and semantic interpretation): eats (S\NP)/NPxy.eats’xyS\NPx.eats’x • The main bottleneck for wide-coverage CCG parsing

  15. Example from Chinese CCGBank

  16. Example from Chinese CCGBank

  17. Example from Chinese CCGBank

  18. Example from Chinese CCGBank

  19. Example from Chinese CCGBank

  20. Summary • CCG is a lexicalized grammar formalism • “rules” of are extremely general, just like HPSG schemata • CCG is nearly context-free • Weakly equivalent to TAG • CCG has a flexible constituent structure • CCG has a transparent syntax-semantics interface • Every syntactic category and combinatory rule has a semantic interpretation • Movement or traces don’t exist • CCG rules are type-driven, not structure-driven • E.g. intransitive verbs and VPs are indistinguishable

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