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Growing Trees

Growing Trees. Lec.7 . The relationship between Phrase S tructure R ules & Phrase S tructure T rees. Any grammatical structure can be represented by tress, which in turn can be specified by phrase structure rules. The relationship between Phrase Structure Rules & Phrase Structure Trees.

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Growing Trees

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  1. Growing Trees Lec.7

  2. The relationship between Phrase Structure Rules & Phrase Structure Trees • Any grammatical structure can be represented by tress, which in turn can be specified by phrase structure rules.

  3. The relationship between Phrase Structure Rules & Phrase Structure Trees • Phrase structure rules = tests that trees must pass to be grammatical • Each syntactic category mentioned in the tree is examined to see if the syntactic categories immediately beneath it agree with the phrase structure rules. e.g. NP Det N, or Det N PP

  4. The conventions of generating trees • The S occurs at the top of the tree despite being called the root • Find a rule with an S on the left side of the arrow, & put the categories on the right side below the S, as shown here: S NP Aux VP

  5. The conventions of generating trees • Once started, continue by matching any syntactic category at the bottom of the partially constructed tree to a category on the left side of a rule, then expand the tree with the categories on the right side: S NP Aux VP Det N

  6. The conventions of generating trees • the VP rule is actually 4 rules abbreviated by parentheses. They are VP  V VP  V (NP) VP  V (PP) VP  V (Adv.) VP  V (NP) (PP)

  7. The conventions of generating trees • Once started, continue by matching any syntactic category at the bottom of the partially constructed tree to a category on the left side of a rule, then expand the tree with the categories on the right side: S NP Aux VP Det N V PP

  8. Syntactic Categories Phrasal Categories (=S) NP, VP, AP, PP Lexical Categories N, V, Adj., Adv. Functional Categories Det. & Aux.

  9. Note • Since there is an infinite number of possible sentences in every language, there are limitless number of trees, but only a finite set of phrase structure rules that specify the trees allowed by a grammar of the language

  10. Home work • The boat sailed up the river • A girl laughed at the monkey • The sheepdog rolled in the mud • The lions roared in the jungle

  11. Structural Ambiguities • Certain ambiguous sentences have more than one phrase structure tree, each corresponding to a different meaning. • E.g. 1. The boysaw the manwith the telescope 2. The boysaw the man with the telescope

  12. 1. The boysaw the manwith the telescope S NP AUX VP past Det. N V NP PP VP  VP N PP

  13. 2. The boysaw the man with the telescope S NP AUX VP Past Det. N V NP Det. N PP NP  Det. N PP

  14. Trees that cannot grow S NP Aux Det. N * The man It lacks……………… S Aux VP Past V NP Det. N *saw a buffalo It lacks……………….

  15. Trees that cannot grow NP N Det. *Boy the ……………………

  16. More phrase structure rules Many English have structures that are not accounted for by the phrase structure rules given so far, such as: • Pretty girls whispered swiftly • The cat and the dog were friends • The teacher believes that the student knows the answer

  17. Pretty girls whispered swiftly S NP Aux VP APpast Adj. N V Adv. pretty girls whispered swiftly

  18. Note that • Determiner is optional in the NP • A new phrasal category & two lexical categories appear in the tree: (AP), (Adj.), & (Adv.) • So, we can suggest the following modifications to both NP & VP rules • NP  (Det.) (AP) N (PP) • VP  V (NP) (PP) (Adv.) • AP  Adj. (PP)

  19. The cat and the dog were friends S NP Conj. NP the cat and the dog

  20. Note that • The NP is a coordinate structure. • NP  NP conj. NP

  21. The teacher believes that the student knows the answer S NP Aux VP Det. N present V S the teacher believes the student knows the answer

  22. The teacher believes that the student knows the answer S NP Aux VP Det. N present V CP Comp S the teacher believes that the student ……

  23. CP category • The suggested rule for the category CP: CP  Comp S • In addition, we need another VP rule: VP  V CP • If we combine this with the previous VP rules, we get: VP  V (NP) (PP) (CP)

  24. Phrase structure rules • S  NP Aux. VP • NP  (Det.) (AP) N (PP) • VP  V (NP) (PP) (Adv.) (CP) • PP  P NP • AP  Adj. (PP) • CP  Comp S

  25. Homework • Cathy rushed quickly into the store • The teacher found out that the book was available • The doctor or the pharmacist were mistaken!

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