Algorithm Schemata and Data Structures in Syntactic Processing

Algorithm Schemata and Algorithm Schemata and Data Structures in Data Structures in Syntactic ProcessingSyntactic Processing

By Martin KayBy Martin Kay

발표자 발표자 : : 임성신임성신

E-mail : [email protected] : [email protected]

[email protected]@pusan.ac.kr

ContentsContents

ParsingParsing Top-down parsingTop-down parsing Buttom-up parsingButtom-up parsing Chart parsingChart parsing

CKYCKYBottom-up Chart ParsingBottom-up Chart ParsingTop-down Chart ParsingTop-down Chart Parsing


What is parsing?What is parsing?

parsing involves recognising an input string parsing involves recognising an input string and assigning a structure to itand assigning a structure to it

parsing involves:parsing involves:a grammar e.g. a context-free grammara grammar e.g. a context-free grammaran input stringan input stringa parsing algorithm: a set of instructions for a parsing algorithm: a set of instructions for

applying the grammar to the input stringapplying the grammar to the input stringe.g. whether to use top-down or bottom-up e.g. whether to use top-down or bottom-up methodsmethods


Applications of ParsingApplications of Parsing

grammar checking in word processing grammar checking in word processing systemssystems

as a basis for semantic analysisas a basis for semantic analysis to support applications of NLP such as to support applications of NLP such as

machine translationmachine translationquestion answeringquestion answeringinformation extractioninformation extraction


Top-down production Top-down production 예문 예문 : radio broadcasts pay: radio broadcasts pay


S

NP VP

D N V NP

D N

the dog saw the cat

StartTop-down Parsing


Buttom-up ProductionButtom-up Production


S

NP VP

D N V NP

D N

the dog chased the cat

Start

Bottom-up parsing


Parsed SentenceParsed Sentence

the boy hits the dog with a rod

Det NounDet Noun Det Noun

NPNP

NP

PrepVerb

PPVP

VP

S


Top-down ParsingTop-down Parsing


S

NPVerb

Det Noun

NP VP

Det Noun

PPVP

NPVerb

Det Noun

NPPrep

Det Noun


Bottom-up ParsingBottom-up Parsing


Det

theDet boy

Noun

Noun

NP

NP

Verb

hitsVerb the

Det

Det dog

Noun

NounNP Verb

NP

NP

VP

NP VPS

S with

Prep

Prep a

Det

Det rod

Noun

Noun

NP

S Prep NP

PP

S PP


Bottom-up ParsingBottom-up Parsing

with a rodthe boy hits the dog

Det NounDet Noun

NP

NP

Verb

VP

NP VP with PrepPrep a

Det

Det rod

Noun

NounNP VP Prep NPNP

PP

NP VP PP

VP

NP VP

S

S


Chart ParsingChart Parsing chart parsing is a form of dynamic chart parsing is a form of dynamic

programmingprogramming dynamic programming solves problems by dynamic programming solves problems by

filling in tables with solutions to sub-filling in tables with solutions to sub-problemsproblems

when complete, the tables contain all the when complete, the tables contain all the solutions to the sub-problems needed to solutions to the sub-problems needed to solve the problemsolve the problem

in chart parsing, this involves storing in chart parsing, this involves storing subtrees for constituents that are foundsubtrees for constituents that are found

once found and stored, subtrees can be once found and stored, subtrees can be looked up - this avoids reparsinglooked up - this avoids reparsing


CKY(Cocke-Kasami-Younger)CKY(Cocke-Kasami-Younger)


Det Noun Verb Det Noun Prep Det NounNP NP NP

VP PP

SVP

S


예문 예문 : Failing students looked hard.: Failing students looked hard.

1.1. S S → NP → NP VPVP2.2. NP NP → A → A NN3.3. NP NP → PRP→ PRP NN4.4. VPVP → V→ V AA5.5. VPVP → V→ V AVAV6.6. AA → failing, hard, …→ failing, hard, …7.7. PRPPRP → failing, …→ failing, …8.8. NN → students, …→ students, …9.9. VV → looked, …→ looked, …10.10.AVAV → hard, …→ hard, …


Bottom-up Chart ParsingBottom-up Chart Parsing(1/4)(1/4)

Failing student looked hard

A

PRP

N V A

AVNP

N

NP

N

N

N

S

S

VP

VP




AAV

V

VP

VAV

VP

VA

AV

A




PRP

NP

NN

S

VP

PRP

NP

NN

S

VP

VP

VAV

AV

A

VP

V A




ANP

NN

S

VP

ANP

NN

S

VP

VP

VAV

AV

VP

VAA


Parsing Graph & TableParsing Graph & Table


Top-down Chart Parsing Top-down Chart Parsing Initial Step Initial Step


A N V A

AVPRP

?S


Top-down Chart Parsing(1/6)Top-down Chart Parsing(1/6)


?S S

?NP

?VP

NP?

A?

N

NP?

PRP?

N




NP?

A?

N

A

S?

NP?

VP

N

NPFailing

A?

N

NPFailing

Astudent

N

NPFailing

Astudent

N?

VP S




PRP N

S?

NP

?

VP

NP?

PRP

?

NNP

Failing

PRP

?

N

NPFailing

PRP

student

N

NPFailing

PRPstudent

N?

VP S




V A

VP?

V

?

A VPlooked

V

?

AVP

looked

V

hard

A




V AV

VP?

V

?

AV VPlooked

V

?

AVVP

looked

V

hard

AV




VPlooked

V

hard

A

NPFailing

Astudent

N?

VP SNP

FailingAstudent

N SVP

lookedV

hardA


Parsing Graph & TableParsing Graph & Table

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Algorithm Schemata and Data Structures in Syntactic Processing