Carnegie Mellon School of Computer Science Copyright © 2007, Carnegie Mellon. All Rights Reserved....

1Carnegie MellonSchool of Computer Science LTI Grammars and Lexicons

Grammar WritingLecture 5

11-721 Grammars and Lexicons

Teruko Mitamura

teruko@cs.cmu.eduwww.cs.cmu.edu/~teruko

Schedule: November 19, 2007• Review of “bird.gra” • Review of “bird2.gra”• Character-based Parsing vs. Word-based

Parsing • Morphology• Start a new grammar exercise (4)

Bird.gra review General Problems

• Incomplete F-structure • Incorrect F-structure• Not enough constraints in the rule • Unification problems

Incomplete F-structuresDeterminer information is missing from f-

structure“A bird flies” and “The bird flies” showed the

same F-structure((subj ((agreement 3sg) (number sg) (root bird))) (form present) (agreement 3sg) (root fly))

Complete F-structure• Contains all the necessary grammatical

information• Be able to reconstruct the original sentence “A bird flies”((SUBJ ( (NUMBER SG) (AGREEMENT 3SG) (ROOT BIRD) (DET ((NUMBER SG) (DEFINITENESS -) (ROOT A))) )) (FORM PRESENT) (AGREEMENT 3SG) (ROOT FLY))

• Some feature structures are redundant

Incomplete F-structures (2)

Grammar problem:(<NP> < == > (<DET> <N>) ( ((x1 number) = (x2 number)) (x0 = x2) ))

Not Enough ConstraintsThe singular noun without determiner can

become NP. “Bird flies” may parse. (<NP> < == > (<N>) ((x0 = x1)))

Problem: No constraint for number. ((x1 number) =c pl)

Be Aware of Unification

(<NP> < == > (<DET> <N>) ((x0 = x1) (x0 = x2)))(<DET> < -- > (t h e) (((x0 definiteness) = +)))(<N> < -- > (b i r d) (((x0 root) = bird) ((x0 number) = sg) ((x0 agreement) = 3sg)))

Be Aware of Unification (cont.)(<NP> < == > (<DET> <N>) ((x0 = x1) (x0 = x2)))(<DET> < -- > (t h e) (((x0 definiteness) = +) ((x0 root) = the)))(<N> < -- > (b i r d) (((x0 root) = bird) ((x0 number) = sg) ((x0 agreement) = 3sg)))

Frequently Seen Problems• Test equations come before Action (x0 = x2) ;action ((x1 agreement) = (x2 agreement)) ;test• No “root” info in f-structure• When submitted:

– Write your full name in the grammar– Write more comments in the grammar– Turn off (dmode 2) or trace

• Print out the grammar and results files. – lpr –P<printer name> <filename> e.g. lpr –Pshakthi bird.gra

Review: Bird 2 Grammar

• Goal: To learn more on unification• Some Problems:

– Not scalable semantic features ((x0 semclass) = Morris)– Incomplete f-structures– Incorrect f-structures

Grammar Exercise (3) Test Sentences

"A bird flies“"Birds fly“"The bird flies“"The birds fly“"The cat runs“"The cats run““Morris runs““Morris meows“"Cats meow“"A cat meows”"The cats meow“"The penguins run”"A penguin runs"

Grammar Exercise (3) Test Sentences (fail)

"A bird fly" "A birds flies" "Birds flies" "Bird flies" "The bird fly" "The birds flies"

Test Sentences (fail) "The cat flies" "The cats fly" "The cat run" "A cat meow" “Morris meow" “Morris flies" "The bird meows" "A penguin meows" “Penguins meow" "The penguin flies"

Semantic Category

Bird fly, run, *meowCat *fly, run, meowPenguin *fly, run, *meow

Semantic Features (noun)

Bird (sem-class bird)Cat (sem-class cat)Penguin (sem-class penguin)--------------------------------- (animate +)

Semantic Features (verb)Fly ((subj sem-class) = bird)Meow ((subj sem-class) = cat)Run ((subj animate) = +)

Unification(<N> <--> (c a t s)

(((x0 root) = cat) ((x0 number) = pl) ((x0 animate) = +) ((x0 sem-class) = cat) ((x0 agreement) = pl)))

(<V> <--> (m e o w) (((x0 root) = meow) ((x0 agreement) = pl) ((x0 subj animate) = +) ((x0 subj sem-class) = cat) ((x0 form) = present)))

Unification(<S> <==> (<NP> <VP>)(((x1 agreement) = (x2 agreement)) ((x0 subj) = x1) (x0 = x2)))

Character-based ParsingMorphological rules can be parsedInput string: tabeta eat-past

taberu eat-present

(<v-class-1> < -- > (<v-class-1> r u)((x0 = x1) ((x0 tense) = present)))

(<v-class-1> < -- > (<v-class-1> t a)((x0 = x1) ((x0 tense) = past)))

(<v-class-1> < -- > (t a b e)(((x0 root) = taberu))

Japanese morphologytabe-sase-rare-taeat-caus-pass-past(<v-class-1> < -- > (t a b e)

(((x0 root) = taberu))) (<v-class-1> < -- > (<v-class-1> s a s e)

(((x1 pass) = *undefined*) ((x1 tense) = *undefined*) (x0 = x1) ((x0 caus) = +)))

(<v-class-1> < -- > (<v-class-1> r a r e)(((x1 tense) = *undefined*) (x0 = x1) ((x0 pass) = +)))

(<v-class-1> < -- > (<v-class-1> t a)((x0 = x1) ((x0 tense) = past)))

Tabeta eat-pastTabe-sase-ta eat-caus-pastTabe-rare-ta eat-pass-pastTabe-sase-rare-ta eat-caus-pass-past

*tabe-rare-sase-ta eat-pass-caus-past*tabe-ta-sase-rare eat-past-caus-pass*tabe-ta-rare-sase eat-past-pass-caus*tabe-rare-ta-sase eat-pass-past-caus*tabe-sase-ta-rare eat-caus-past-pass*tabe-rare-sase eat-pass-caus*tabe-ta-sase eat-past-caus

Word-based Parsing(<N> < -- > (sushi) (((x0 = root) = sushi)))Instead of: (<N> < -- > (s u s h i) (((x0 = root) = sushi)))For parsing: (parse-list list of symbols $)e.g. (parse-list ‘(a bird flies $))

Grammar Exercise (4)

• Start grammar exercise (4): mlb.gra• Files are in /afs/cs/project/cmt-55/lti/Lab/Modules/ GNL-721/2007/• Test file: mlb-test.lisp

Next Class: Nov 26

• Return bird2.gra• Return Assignment #1• Grammar Writing Project Evaluation

Criteria• Finish mlb.gra• Start a new exercise

Carnegie Mellon School of Computer Science Copyright © 2007, Carnegie Mellon. All Rights Reserved....

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