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CS 182 Sections 103 - 104

Explore the concepts of formal grammar, parsing techniques, and language learning in linguistics. Learn how to analyze sentences and improve language representation.

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CS 182 Sections 103 - 104

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  1. CS 182Sections 103 - 104 Eva Mok (emok@icsi.berkeley.edu) April 21, 2004

  2. Announcements • a9 out sometime Thursday, due Wednesday April 22nd, 11:59pm • How’s your progress on the BBS articles?

  3. Schedule • Last Week • SHRUTI • Formal Grammar and Parsing • This Week • Construction Grammar, ECG • Psychological model of sentence processing • Next Week • Language learning • Learning ECG

  4. Quiz • What is top-down parsing? Using a plausible CFG grammar, what is the top down parse of “Pat ate the kiwi”? • How well can CFGs represent English? What are some mechanisms for improvement? • What are constructions? • What is the difference between subcasing and evoking another schema or construction?

  5. Quiz • What is top-down parsing? Using a plausible CFG grammar, what is the top down parse of “Harry likes the cafe”? • How well can CFGs represent English? What are some mechanisms for improvement? • What are constructions? • What is the difference between subcasing and evoking another schema or construction?

  6. Grammar • A grammar is a set of rules defining a formal language • an example is right-regular grammar • a more common example is Context-Free Grammar   β •  : single non-terminal • β : any combination of terminals and non-terminals S  NP VP NP  Det Noun | ProperNoun VP  Verb NP | Verb PP PP  Preposition NP Noun  kiwi | orange | store ProperNoun  Pat | I Det  a | an | the Verb  ate | went | shop Preposition  to | at

  7. Top Down Parsing: Pat ate the kiwi • start from S and apply all applicable rules • forward search (use your favorite search algorithm…) S S  NP VP NP  Det Noun | ProperNoun VP  Verb NP | Verb PP PP  Preposition NP NP VP Det Noun VP ProperNoun VP Noun  kiwi | orange | store ProperNoun  Pat | I Det  a | an | the Verb  ate | went | shop Preposition  to | at a Noun VP an Noun VP the Noun VP … a kiwi VP a orange VP a store VP succeed when you encounter Pat ate the kiwiin a state without any non-terminals (DFS)

  8. Bottom Up Parsing: Pat ate the kiwi • start from the sentence and try to match non-teriminals to it • backward search (use your favorite search algorithm…) S S  NP VP NP  Det Noun | ProperNoun VP  Verb NP | Verb PP PP  Preposition NP NP VP NP Verb NP Noun  kiwi | orange | store ProperNoun  Pat | I Det  a | an | the Verb  ate | went | shop Preposition  to | at NP Verb DetNoun NP Verb Det kiwi NP Verb the kiwi NP ate the kiwi succeed when you encounter Sin a state by itself ProperNoun ate the kiwi Pat ate the kiwi (DFS)

  9. Quiz • What is top-down parsing? Using a plausible CFG grammar, what is the top down parse of “Harry likes the cafe”? • How well can CFGs represent English? What are some mechanisms for improvement? • What are constructions? • What is the difference between subcasing and evoking another schema or construction?

  10. Notice the ungrammatical and/or odd sentences that we can generate? • * Pat ate a orange • *Pat shop at the store • *Pat went a store • ?Pat ate a store • ?The kiwi went to an orange S  NP VP NP  Det Noun | ProperNoun VP  Verb NP | Verb PP PP  Preposition NP Noun  kiwi | orange | store ProperNoun  Pat | I Det  a | an | the Verb  ate | went | shop Preposition  to | at need to capture agreement, subcategorization, etc you could make many versions of verbs, nouns, dets  cumbersome

  11. Pat number : SG person : 3rd agreement I number : SG person : 1st agreement Went agreement Shop number : person : 1st agreement Unification Grammar • Basic idea: capture these agreement features for each non-terminal in feature structures • Enforce constraints on these features using unification rules • VP  Verb NP • VP.agreement ↔ Verb.agreement • S  NP VP • NP.agreement ↔ VP.agreement

  12. Quiz • What is top-down parsing? Using a plausible CFG grammar, what is the top down parse of “Harry likes the cafe”? • How well can CFGs represent English? What are some mechanisms for improvement? • What are constructions? • What is the difference between subcasing and evoking another schema or construction?

  13. CAFE Embodied constructions ECG Notation Form Meaning constructionHARRY form : /hEriy/ meaning : Harry Harry constructionCAFE form : /khaefej/ meaning : Cafe cafe Constructions have form and meaning poles that are subject to type constraints.

  14. Quiz • What is top-down parsing? Using a plausible CFG grammar, what is the top down parse of “Harry likes the cafe”? • How well can CFGs represent English? What are some mechanisms for improvement? • What are constructions? • What is the difference between subcasing and evoking another schema or construction?

  15. A schema hierarchy of objects (Nomi) schema Entity schema Physical-Object subcase of Object, Place schema Human subcase of Animate roles sex schema Place schema Animate subcase of Physical-Object roles animacy constraints animacy ← true schema Object subcase of Entity schema Nomi subcase of Human sex ← female slot filler schema Referent subcase of Entity roles category distribution boundedness number gender accessibility resolved-ref schema Toy subcase of Manipulable-Object schema Manipulable-Object subcase of Physical-Object schema Cup subcase of Manipulable- Object schema Ball subcase of Toy

  16. The schemas we just defined Entity Place Referent Object Physical-Object Food Manipulable-Object Animate Cup Toy Human Cake Juice Ball Book Block Doll Bed Nomi Mother Father

  17. A schema hierarchy of actions (Nomi) schema Action roles agent : Entity schema CauseMove subcase of DirectedAction, Move roles causer : Human mover : Physical-Object motion : Move constraints motion.mover ↔ mover motion.agent ↔ causer motion.direction ↔ direction agent ↔ causer patient ↔ mover type constraint schema DirectedAction subcase of Action roles patient : Entity identification constraint schema Move subcase of Action roles mover : Entity direction : Place

  18. The schemas we just defined Action Directed Action Move Cause-Move Transfer JointMove

  19. Constructions, finally (Nomi) construction Ref-Expr form : Schematic-Form meaning : Referent construction Cup-Cn level 0 subcase of Ref-Expr form : Word self.f.orth ← “cup" meaning evokes Cup as n self.m.category ↔ n self.m.resolved-ref ↔ n construction Nomi-Cn level 0 subcase of Ref-Expr form : Word self.f.orth ← "Nomi" meaning evokes Nomi as n self.m.category ↔ n self.m.resolved-ref ↔ n local name fancy way of saying that the category of the referent is Nomi

  20. Constructions, finally (Nomi) construction Motion-Verb meaning : Move construction Cause-Motion-Verb subcase of Motion-Verb meaning : CauseMove construction Get-Cn level 0 subcase of Cause-Motion-Verb form : Word self.f.orth ← "get" lexical construction

  21. Constructions, finally (Nomi) construction Transitive-Cn level 2 constructional constituents agt : Ref-Expr v : Cause-Motion-Verb obj : Ref-Expr form agt.f before v.f v.f before obj.f meaning v.m.agent ↔ agt.m.resolved-ref v.m.patient ↔ obj.m.resolved-ref smaller constructions that it takes ordering constraints on the constituents

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