Natural Language Processing Ch3. Parsing with PSG

More documents

Recommendations

Info

NP à DET N CL à WH VP Here CL is WH clause, it = (that + VP) VP à V It is not CNF and must be transformed to: VP à V NP VP à V that S VP à V TH TH à WH S VP à cough | walk | … It must be transformed to: Here TH is that-clause, it = (that + S). • Calculation of the b ij of non-terminal symbols: --To arrange POS non-terminal symbols and calculate their b ij “The table that lacks a leg hits Jack” DET N WH V DET N V PrN (NP) b 11 b 21 b 31 b 41 b 51 b 61 b 71 b 81 --To calculate the b ij of phrase non-terminal symbols S 18 (S à NP VP) NP3 (NP à NP CL) b 16 CL (CL à WH VP) b 34 VP2 (VP à V NP) b 43 NP1 (NP à DET N) NP2 (NP à DET N) VP1 (VP à V NP) b 12 b 52 b 72 DET N WH V DET N V NP b 11 b 21 b 31 b 41 b 51 b 61 b 71 b 81 The table that lacks a leg hits Jack Fig. 18
ij (NP1): i=1. j=1+1=2 b ij (NP2): i=5, j=1+1=2 b ij (VP1): i=7, j=1+1=2 b ij (VP2): i=4, j=1+2=3 b ij (CL): i=3, j=1+3=4 b ij (NP3): i=1, j=2+4=6 b ij (S): i=1, j=2+6=8 The length of this sentence is 8, and we get box line number of S is also 8, so the sentence was recognized. graph. By the CYK approach, we can create the pyramid in Fig. 15. This pyramid is also a tree 3.4.2.5 another example Now we use CYK to parse the sentence “book that flight”. If the rules of our CFG are as above rules which we used to parse this sentence: 1. S à VP 2. VP à Verb NP 3. NP à Det Nominal 4. Nominal à Noun The form of rule-1 is not CNF because its RHS includes only one single Non-terminal VP. Therefore we have to combine rule-1 with rule-2 which has CNF. In this case, rule-1 and rule-2 can be changes as following CNF: S à Verb NP The form rule-4 is not CNF because its RHS includes only one single Non-terminal symbol. Therefore we have to combine rule-4 with rule-3 which has CNF. In this case, rule-4 and rule-3 can be changed as following CNF: NP à Det Noun Now the rules with CNF can be: S à Verb NP NP à Det Noun The CYK result of this sentence can be represented in following table: S (S à Verb NP) b 13 NP (NP à Det Noun) b 22 Verb Det Noun b 11 b 21 b 31 Book that flight
Page 1 and 2: Natural Language Processing Prof. F
Page 3 and 4: Fifth ply: VP NP NP NP Nominal Nomi
Page 5 and 6: S VP Verb NP Book Fifth ply: S S VP
Page 7 and 8: [Success ! ] 3.2.2 Comparing Top-Do
Page 9 and 10: Noun is the left-corner of Nominal.
Page 11 and 12: à à 1 1 n +
Page 13 and 14: NP NP PP Nom NP Det Noun Prep Prop-
Page 15 and 16: 3.4.1.2 Three operators in Early al
Page 17 and 18: The Earley algorithm just described
Page 19 and 20: Chart [0] à .S [0,0] Dummy start s
Page 21 and 22: Example-2: using Earley algorithm t
Page 23 and 24: PrN à ASIANA. [9,10] Scanner NPàP
Page 25 and 26: 3.4.2. CYK approach: CYK approach i
Page 27: à à à

Natural Language Processing Ch3. Parsing with PSG

Create successful ePaper yourself

Delete template?

Save as template?