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

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Lexicalization Proposition (Joshi and Schabes, 1997) Finitely ambiguous CFGs can be strongly lexicalized by TAGs. Proposition (Joshi and Schabes, 1997) Finitely ambiguous TAGs are closed under strong lexicalization. 26 / 52
Further Formal Properties of TAL <strong>Tree</strong>-<strong>Adjoining</strong> Languages (TAL) have interesting formal properties, similar to those of context-free languages: TALs are closed under union, concatenation, iteration, substitution and intersection with regular languages. There is a pumping lemma for TAL. There is a class of automata which recognizes TAL: Embedded Push-Down Automata (EPDA). TALs can be parsed in polynomial time. 27 / 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 and 22: Adjunction Definition (Adjunction)
Page 23 and 24: Adjunction Constraints Given TAG G
Page 25: Lexicalization Example (strong lexi
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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