Lexicalized Tree-Adjoining Grammars (LTAG) - ad-teaching.infor...
Lexicalized Tree-Adjoining Grammars (LTAG) - ad-teaching.infor... Lexicalized Tree-Adjoining Grammars (LTAG) - ad-teaching.infor...
Lexicalization A grammar is lexicalized if each elementary structure is associated with at least one lexical item (terminal symbol), called its anchor. Example (Lexicalized CFG) S → Mary V ∣ ∣ John V V → runs Example (Non-lex. CFG) S → N V N → Mary ∣ John V → runs Weak lexicalization of a grammar: Find a lexicalized grammar generating the same string language. Strong lexicalization of a grammar: Find a lexicalized grammar generating the same tree language. 10 / 52
Lexicalization Example (Lexicalized initial trees) NP S S N NP↓ VP NP↓ VP Mary V eats NP↓ V takes NP↓ PP P NP into N account Example (Non-lexicalized initial trees) NP S S D↓ N↓ NP↓ VP↓ NP↓ VP V↓ NP↓ 11 / 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: Cross-Serial Dependencies Example (
- 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 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
Lexicalization<br />
Example (<strong>Lexicalized</strong> initial trees)<br />
NP<br />
S<br />
S<br />
N<br />
NP↓<br />
VP<br />
NP↓<br />
VP<br />
Mary<br />
V<br />
eats<br />
NP↓<br />
V<br />
takes<br />
NP↓<br />
PP<br />
P NP<br />
into N<br />
account<br />
Example (Non-lexicalized initial trees)<br />
NP<br />
S<br />
S<br />
D↓<br />
N↓<br />
NP↓<br />
VP↓<br />
NP↓<br />
VP<br />
V↓<br />
NP↓<br />
11 / 52
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