Lexicalized Tree-Adjoining Grammars (LTAG) - ad-teaching.infor...

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Adjunction Example (Adjunction) Adv S yesterday S ∗ S NP VP N V NP Mary S saw D a N cat Adv S yesterday NP VP N V NP Mary saw D N a A green N cat N A green N ∗ 22 / 52
Adjunction Constraints Given TAG G = (N, T , I , A, S) We specify for each node n of a tree in I ∪ A: OA ∈ {⊥, ⊤} : obligatory adjunction Boolean specifying whether adjunction at n is mandatory SA ⊆ A : selective adjunction Set of auxiliary trees authorized for adjunction at n Also often used: NA ∈ {⊥, ⊤} : null adjunction Shorthand for the special case OA = ⊥ ∧ SA = ∅ Remarks • OA = ⊤ ∧ SA = ∅ is not allowed. • β ∈ SA(n) only if root label of β equal to label of n. • Substitution nodes must have NA = ⊤. 23 / 52
Page 1 and 2: Lexicalized Tree-Adjoining Grammars
Page 3 and 4: Context-Free Grammars Definition (C
Page 5 and 6: Tree-Substitution Grammars Example
Page 7 and 8: Outline 1 Why CFGs are not enough (
Page 9 and 10: Cross-Serial Dependencies Example (
Page 11 and 12: Lexicalization Example (Lexicalized
Page 13 and 14: Lexicalization Example (CFG which i
Page 15 and 16: Outline 1 Why CFGs are not enough (
Page 17 and 18: Initial Trees Definition (Initial T
Page 19 and 20: Substitution Definition (Substituti
Page 21: Adjunction Definition (Adjunction)
Page 25 and 26: Lexicalization Example (strong lexi
Page 27 and 28: Further Formal Properties of TAL Tr
Page 29 and 30: TAG Parsing Parser: Given a string
Page 31 and 32: Recognizing Adjunction But the algo
Page 33 and 34: Dotted Tree We introduce the notion
Page 35 and 36: Chart Items The algorithm stores in
Page 37 and 38: Scan Operations Input string: c 1
Page 39 and 40: Complete Operations 1 2 3 [γ, adr,
Page 41 and 42: Recognizer Algorithm Algorithm (Rec
Page 43 and 44: Complexity of Recognizer Given: n:
Page 45 and 46: Recognizing Substitution Recognizer
Page 47 and 48: LTAG-Spinal Parser LTAG-spinal: Rou
Page 49 and 50: LTAG-Spinal Parser Graphical repres
Page 51 and 52: Conclusion TAG: a grammar formalism

Lexicalized Tree-Adjoining Grammars (LTAG) - ad-teaching.infor...

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