Dependency Parsing Lecture 2
Overview ● Nivre's Arc-Eager / Arc-Standard Algorithm ● Covington's Parsing Strategy ● Pseudo-projective Parsing ● Java ML Libraries - OpenNLP MaxEnt - Mallet - Liblinear
Arc-Standard Algorithm ● Two stacks: - Stack with tokens that still have to be processed ( Input Stack ) - Stack with tokens that already have been processed ( Processed Stack ) ● One set: - Set of predicted dependency pairs ● Initial configuration: - Processed Stack with “0“ on top of it. Input Stack with the whole input on it. ● Terminal configuration: - Empty Processed Stack
Arc-Standard Parsing Algorithm Leftarc ● - Makes the top token of the input stack the head of the top token of the processed stack - Pops the top token from the processed stack Rightarc ● if the top token of the processed stack already has been attached to all of its dependents to the right : - Makes it the head of the top token of the input stack - Pops the top token from the input stack - Moves the top token of the processed stack on top of the input stack Shift ● - Moves the top token of the input stack on top of the processed stack
Input 1 A DT _ _ 2 hearing NN _ _ 3 on IN _ _ 4 the DT _ _ 5 issue NN _ _ 6 is VBZ _ _ 7 scheduled VBN _ _ 8 today NN _ _ 9 . . _ _
Arc-Standard Parsing Example [ ] [0] [9, 8, 7, 6, 5, 4, 3, 2, 1] Shift 0 A 1 hearing 2 on 3 the 4 issue 5 is 6 scheduled 7 today 8 . 9
Arc-Standard Parsing Example [ ] [0, 1] [9, 8, 7, 6, 5, 4, 3, 2] Leftarc 0 A 1 hearing 2 on 3 the 4 issue 5 is 6 scheduled 7 today 8 . 9
Arc-Standard Parsing Example [(1,2)] [0] [9, 8, 7, 6, 5, 4, 3, 2] Shift Det 0 A 1 hearing 2 on 3 the 4 issue 5 is 6 scheduled 7 today 8 . 9
Arc-Standard Parsing Example [(1,2)] [0, 2] [9, 8, 7, 6, 5, 4, 3] Shift Det 0 A 1 hearing 2 on 3 the 4 issue 5 is 6 scheduled 7 today 8 . 9
Arc-Standard Parsing Example [(1,2)] [0, 2, 3] [9, 8, 7, 6, 5, 4] Shift Det 0 A 1 hearing 2 on 3 the 4 issue 5 is 6 scheduled 7 today 8 . 9
Arc-Standard Parsing Example [(1,2)] [0, 2, 3, 4] [9, 8, 7, 6, 5] Leftarc Det 0 A 1 hearing 2 on 3 the 4 issue 5 is 6 scheduled 7 today 8 . 9
Arc-Standard Parsing Example [(1,2), (4,5)] [0, 2, 3] [9, 8, 7, 6, 5] Rightarc Det Det 0 A 1 hearing 2 on 3 the 4 issue 5 is 6 scheduled 7 today 8 . 9
Arc-Standard Parsing Example [(1,2), (4,5), (5,3)] [0, 2] [9, 8, 7, 6, 3] Rightarc PC Det Det 0 A 1 hearing 2 on 3 the 4 issue 5 is 6 scheduled 7 today 8 . 9
Arc-Standard Parsing Example [(1,2), (4,5), (5,3), (3,2)] [0] [9, 8, 7, 6, 2] Shift PC Det NMOD Det 0 A 1 hearing 2 on 3 the 4 issue 5 is 6 scheduled 7 today 8 . 9
Arc-Standard Parsing Example [(1,2), (4,5), (5,3), (3,2)] [0, 2] [9, 8, 7, 6] Leftarc PC Det NMOD Det 0 A 1 hearing 2 on 3 the 4 issue 5 is 6 scheduled 7 today 8 . 9
Arc-Standard Parsing Example [(1,2), (4,5), (5,3), (3,2), (2,6)] [0] [9, 8, 7, 6] Leftarc SBJ PC Det NMOD Det 0 A 1 hearing 2 on 3 the 4 issue 5 is 6 scheduled 7 today 8 . 9
Arc-Standard Parsing Example [(1,2), (4,5), (5,3), (3,2), (2,6), (6,0)] [ ] [9, 8, 7, 6] Shift ROOT SBJ PC Det NMOD Det 0 A 1 hearing 2 on 3 the 4 issue 5 is 6 scheduled 7 today 8 . 9
Arc-Standard Parsing Example [(1,2), (4,5), (5,3), (3,2), (2,6), (6,0)] [6] [9, 8, 7] Shift ROOT SBJ PC Det NMOD Det 0 A 1 hearing 2 on 3 the 4 issue 5 is 6 scheduled 7 today 8 . 9
Arc-Standard Parsing Example [(1,2), (4,5), (5,3), (3,2), (2,6), (6,0)] [6, 7] [9, 8] Rightarc ROOT SBJ PC Det NMOD Det 0 A 1 hearing 2 on 3 the 4 issue 5 is 6 scheduled 7 today 8 . 9
Arc-Standard Parsing Example [(1,2), (4,5), (5,3), (3,2), (2,6), (6,0), (8,7)] [6] [9, 7] Rightarc ROOT SBJ PC Det NMOD Det ADV 0 A 1 hearing 2 on 3 the 4 issue 5 is 6 scheduled 7 today 8 . 9
Arc-Standard Parsing Example [(1,2), (4,5), (5,3), (3,2), (2,6), (6,0), (8,7), (7,6)] [ ] [9, 6] Shift ROOT SBJ PC Det NMOD Det PC ADV 0 A 1 hearing 2 on 3 the 4 issue 5 is 6 scheduled 7 today 8 . 9
Arc-Standard Parsing Example [(1,2), (4,5), (5,3), (3,2), (2,6), (6,0), (8,7), (7,6)] [6] [9] Rightarc ROOT SBJ PC Det NMOD Det PC ADV 0 A 1 hearing 2 on 3 the 4 issue 5 is 6 scheduled 7 today 8 . 9
Arc-Standard Parsing Example [(1,2), (4,5), (5,3), (3,2), (2,6), (6,0), (8,7), (7,6), (9,6)] [ ] [6] Shift ROOT SBJ PC P Det NMOD Det PC ADV 0 A 1 hearing 2 on 3 the 4 issue 5 is 6 scheduled 7 today 8 . 9
Arc-Standard Parsing Example [(1,2), (4,5), (5,3), (3,2), (2,6), (6,0), (8,7), (7,6), (9,6)] [6] [ ] Shift ROOT SBJ PC P Det NMOD Det PC ADV 0 A 1 hearing 2 on 3 the 4 issue 5 is 6 scheduled 7 today 8 . 9
Output 1 A DT 2 DET 2 hearing NN 6 SBJ 3 on IN 2 NMOD 4 the DT 5 DET 5 issue NN 3 OC 6 is VBZ 0 ROOT 7 scheduled VBN 6 PC 8 today NN 7 ADV 9 . . 6 P
Fundamental Parsing Algorithm ● Go through all words in the sentence and for every word j try to combine it with the words 1 .. j- 1 ● Dependents of any given word are more likely to be near it than far away, therefore work backwards through j-1 , j-2 etc, rather than forwards from 1 to 2 , 3 etc. ● Don‘t consider not permissible pairs (don‘t look for a parent if a word already has one, pairs which introduce cycles etc.)
Fundamental Parsing Algorithm Operations ● Given the current word j and a word i < j there are three operations: ● Link(i, j) - Creates a dependency pair with j being the head of i ● Link(j, i) - Creates a dependency pair with i being the head of j ● Shift - Rejects the current pair and moves on
Input 1 She PRP _ _ 2 was VBD _ _ 3 the DT _ _ 4 first JJ _ _ 5 woman NN _ _ 6 to TO _ _ 7 be VB _ _ 8 appointed VBN _ _ 9 FCC NNP _ _ 10 general JJ _ _ 11 counsel NN _ _ 12 . . _ _
Fundamental Parsing Algorithm Example [ ] j: 1 i: 0 {l1=0.016, shift =0.9832} 0 She 1 was 2 the 3 first 4 woman 5 to 6 be 7 appointed 8 FCC 9 general 10 counsel 11 . 12
Fundamental Parsing Algorithm Example [ ] j: 2 i: 1 { l2 =0.8848, l1=0.0083, shift=0.1069} 0 She 1 was 2 the 3 first 4 woman 5 to 6 be 7 appointed 8 FCC 9 general 10 counsel 11 . 12
Fundamental Parsing Algorithm Example [(1,2)] j: 2 i: 0 { l1 =0.6437, shift=0.2547} SBJ 0 She 1 was 2 the 3 first 4 woman 5 to 6 be 7 appointed 8 FCC 9 general 10 counsel 11 . 12
Fundamental Parsing Algorithm Example [(1,2), (2,0)] j: 3 i: 2 { l1 =0.6437, shift=0.2547} ROOT SBJ 0 She 1 was 2 the 3 first 4 woman 5 to 6 be 7 appointed 8 FCC 9 general 10 counsel 11 . 12
Fundamental Parsing Algorithm Example [(1,2), (2,0)] j: 4 i: 3 {l2=0.0224, l1=0.0, shift =0.9776} ROOT SBJ 0 She 1 was 2 the 3 first 4 woman 5 to 6 be 7 appointed 8 FCC 9 general 10 counsel 11 . 12
Fundamental Parsing Algorithm Example [(1,2), (2,0)] j: 4 i: 2 {l1=0.0745, shift =0.9247} ROOT SBJ 0 She 1 was 2 the 3 first 4 woman 5 to 6 be 7 appointed 8 FCC 9 general 10 counsel 11 . 12
Fundamental Parsing Algorithm Example [(1,2), (2,0)] j: 4 i: 1 {l1=0.0, shift =0.9998} ROOT SBJ 0 She 1 was 2 the 3 first 4 woman 5 to 6 be 7 appointed 8 FCC 9 general 10 counsel 11 . 12
Fundamental Parsing Algorithm Example [(1,2), (2,0)] j: 4 i: 0 {l1=5.0E-4, shift =0.9995} ROOT SBJ 0 She 1 was 2 the 3 first 4 woman 5 to 6 be 7 appointed 8 FCC 9 general 10 counsel 11 . 12
Fundamental Parsing Algorithm Example [(1,2), (2,0)] j: 5 i: 4 { l2 =0.8812, l1=0.013, shift=0.1058} ROOT SBJ 0 She 1 was 2 the 3 first 4 woman 5 to 6 be 7 appointed 8 FCC 9 general 10 counsel 11 . 12
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