LING 388: Language and Computers

Sandiway Fong

Lecture 15

10/13

Administrivia

• Reminder– Homework 5 due next Monday

Today’s Topic

• case study– How to implement the passive construction in a

traditional grammar framework• verb inflection• constraints between auxiliary and main verbs• subcategorization and adjuncts

Example Grammar

• grammar so far – including extra arguments for parse tree – and simple determiner-noun agreement– s(s(Y,Z)) --> np(Y), vp(Z). – np(np(Y)) --> pronoun(Y).– np(np(D,N)) --> det(D,Number), common_noun(N,Number).– det(det(the),_) --> [the].– det(det(a),sg) --> [a].– common_noun(n(ball),sg) --> [ball].– common_noun(n(man),sg) --> [man].– common_noun(n(men),pl) --> [men].– pronoun(i) --> [i].– pronoun(we) --> [we].– vp(vp(Y)) --> unergative(Y). – vp(vp(Y,Z)) --> transitive(Y), np(Z).– unergative(v(ran)) --> [ran].– transitive(v(hit)) --> [hit].

• query– ?- s(X,Sentence,[]). Sentence = Prolog list of words

all rules take one extra argument for the parse treehoweverdet and common_nountake two extra arguments:one for the parse treeand one for Number

only one extra argument for the parse tree

verb classes

Passivization

• in English...• passivization applies only to transitive verbs

– I hit the ball (active)– the ball was hit (passive)

transitive(v(hit)) --> [hit].

• i.e. passivization should only apply to verbs encoded in the grammar using the transitive non-terminal

• not for unaccusative or unergative verbs– I arrived– *I was arrived

unaccusative(v(arrived)) --> [arrived].

– We ran– *We were ran/run

unergative(v(ran)) --> [ran].

Passivization

• simple phrase structure– I hit the ball (active)– the ball was hit (passive) A first pass

(simplistic non-movement account)

s

np vp

v np

det n

the ball

hit

i

s

aux

vp

v

np

det n

the ball hitwas

avoiding empty categories for simplicity (can be added, see later slide): the ball was hit e

[the ball]i was hit ti

Passivization

• phrase structure– the ball was hit (passive)

• rules (active sentence)– s(s(Y,Z)) --> np(Y), vp(Z).– vp(vp(Y,Z)) --> transitive(Y), np(Z).– transitive(v(hit)) --> [hit].

• new rules (passive sentence)– vp(vp(A,V)) --> aux(A), transitive(V).

– aux(aux(was)) --> [was].

s

aux

vp

v

np

det n

the ball hitwas

Passivization1. s(s(Y,Z)) --> np(Y), vp(Z). 2. np(np(Y)) --> pronoun(Y).3. np(np(D,N)) --> det(D,Number),

common_noun(N,Number).4. det(det(the),_) --> [the].5. det(det(a),sg) --> [a].6. common_noun(n(ball),sg) --> [ball].7. common_noun(n(man),sg) --> [man].8. common_noun(n(men),pl) --> [men].9. pronoun(i) --> [i].10. pronoun(we) --> [we].11. vp(vp(A,V)) --> aux(A), transitive(V). 12. vp(vp(Y)) --> unergative(Y). 13. vp(vp(Y,Z)) --> transitive(Y), np(Z).14. unergative(v(ran)) --> [ran].15. transitive(v(hit)) --> [hit].16. aux(aux(was)) --> [was].

• query– ?- s(X,[the,ball,was,hit],[]).

• computation tree– ?- s(X,[the,ball,was,hit],[]).

• ?- np(Y,[the,ball,was,hit],L).• ?- vp(Z,L,[]).

– ?- np(Y,[the,ball,was,hit],L).• Y=np(det(the),n(ball)) L=[was,hit]

– ?- vp(vp(A,V),[was,hit],[]).• ?- aux(A,[was,hit],L’).• ?- transitive(V,L’,[]).

– ?- aux(A,[was,hit],L’).• A=aux(was) L’=[hit]

– ?- transitive(V,[hit],[]).• V=v(hit)

• X=s(np(det(the),n(ball)),vp(aux(was),v(hit)))

Passivization

• We are (free to) modify the parse for the VP constituent to include items not found in the input– sometimes this can be very useful– e.g. there are good linguistic reasons why we might prefer to

write– vp(vp(Aux,vp(V,np(trace))),Number) --> aux(Aux,Number),

transitive(V,Ending), {Ending = en}.

instead, which produces:s

aux

vp

v

np

det n

the ball

hit

was

vp

np

trace

Passive Morphology

• verbal inflection– hit eat– hits eats (-s)– hit ate (-ed)– hit eaten (-en)

• verbal inflection and passive morphology• rule: (passive) be V-en

– was hit (ambiguous between -ed and -en)– *was ate (-ed)– was eaten (-en)

• how to implement this restriction?– vp(vp(A,V)) --> aux(A), transitive(V).

• idea– use an extra argument to indicate the verb form for transitive

other morphological rules(progressive) be V-inge.g. was eating(passive+progressive)e.g. was being eaten

Passive Morphology

• verbal inflection– eat (root)– eats (-s)– ate (-ed)– eaten (-en)

• use an extra argument to signal the inflected form, e.g.– transitive(v(eat),root) --> [eat].– transitive(v(eat-s),s) --> [eats].– transitive(v(eat-ing),ing) --> [eating].– transitive(v(eat-ed),ed) --> [ate].– transitive(v(eat-en),en) --> [eaten].

• original rule– vp(vp(A,V)) --> aux(A), transitive(V).

• modified rule– vp(vp(A,V)) --> aux(A), transitive(V,en).equivalentlyvp(vp(A,V)) --> aux(A), transitive(V,Ending),

{Ending=en}.

Constraint for -en realized by Prolog pattern-matching

Passive Morphology

• grammar rules (partial)– transitive(v(eat),root) --> [eat].– transitive(v(eats),s) --> [eats].– transitive(v(ate),ed) --> [ate].– transitive(v(eaten),en) --> [eaten].– vp(vp(A,V)) --> aux(A), transitive(V,en).– aux(aux(was)) --> [was].

• query– ?- vp(X,[was,eaten],[]).

• computation tree– ?- vp(X,[was,eaten],[]). X=vp(A,V)

• ?- aux(A,[was,eaten],L).• ?- transitive(V,en,L,[]).

– ?- aux(A,[was,eaten],L).• A=aux(was) L=[eaten]

– ?- transitive(V,en,[eaten],[]).• V=v(eaten)

example: was eaten

Passive Morphology

• grammar rules (partial)– transitive(v(eat),root) --> [eat].– transitive(v(eats),s) --> [eats].– transitive(v(ate),ed) --> [ate].– transitive(v(eaten),en) --> [eaten].– vp(vp(A,V)) --> aux(A), transitive(V,en).– aux(aux(was)) --> [was].

• query– ?- vp(X,[was,ate],[]).

• computation tree– ?- vp(X,[was,ate],[]). X=vp(A,V)

• ?- aux(A,[was,ate],L).• ?- transitive(V,en,L,[]).

– ?- aux(A,[was,ate],L).• A=aux(was) L=[ate]

– ?- transitive(V,en,[ate],[]).• No

example: *was ate

attemptedmatch fails

Subject in By-Phrase

• phrase structure– I hit the ball (active)– the ball was hit (passive)– the ball was hit by me (passive + subject in by-phrase)

optional prepositional phrase (PP)is adjoined to the verb phrase (VP)

s

aux

vp

v

np

det n

the ball

hitwas

vp pp

p np

by me

s

aux

vp

v

np

det n

the ball hitwas

Subject in By-Phrase • phrase structure

– I hit the ball (active)– the ball was hit (passive)– the ball was hit by me (passive + subject in by-phrase)

• add PP rules– pp(pp(P,NP)) --> preposition(P), np(NP).– preposition(p(by)) --> [by].

• add VP adjunction rule– vp(vp(VP,PP)) --> vp(VP), pp(PP).

• add pronoun rule– np(np(Y)) --> pronoun(Y).– pronoun(i) --> [i].– pronoun(we) --> [we].– pronoun(me) --> [me].

• there is a Case Constraint – (not implemented here)– by me– *by I– *me hit the ball

s

aux

vp

v

np

det n

the ball

hitwas

vp pp

p np

by me

Other Constraints

• examples– I hit the ball (active)– the ball was hit (passive)– the ball was hit by me (passive + by-phrase)– *the ball were hit by me– *the balls was hit by me – the balls were hit by me

• Subject-Verb Agreement Rule– subject must agree with the verb for number

– np(np(D,N)) --> det(D,Number), common_noun(N,Number).– common_noun(n(ball),sg) --> [ball].– common_noun(n(balls),pl) --> [balls].

– np(np(D,N),Number) --> det(D,Number), common_noun(N,Number).

s

aux

vp

v

np

det n

the ballballs

hitwaswere

Other Constraints

• examples– the ball was hit by me (passive + by-phrase)– *the ball were hit by me– *the balls was hit by me – the balls were hit by me

• Subject-Verb Agreement Rule– subject must agree with the verb for number

– must propagate number feature up the tree!

– np(np(D,N),Number) --> det(D,Number),common_noun(N,Number). – common_noun(n(ball),sg) --> [ball].– common_noun(n(balls),pl) --> [balls].

– s(s(Y,Z)) --> np(Y,Number), vp(Z).

– s(s(Y,Z)) --> np(Y,Number), vp(Z,Number).

s

aux

vp

v

np

det n

the ballballs

hitwaswere

numbernumber number

numbernumber

Grammar so far

• new additions today– verbal inflection and

passive morphology• (passive) be V-en

– PP by-phrase• “by me”

– Subject-Verb Agreement Rule

• “the ball/balls was/were”

• grammar is still not fully implemented– see underscores “-”

for Subject-Verb Agreement

1. s(s(Y,Z)) --> np(Y,Number), vp(Z,Number). 2. np(np(Y),_) --> pronoun(Y).3. np(np(D,N),Number) --> det(D,Number),

common_noun(N,Number).4. det(det(the),_) --> [the].5. det(det(a),sg) --> [a].6. common_noun(n(ball),sg) --> [ball].7. common_noun(n(balls),pl) --> [balls].8. common_noun(n(man),sg) --> [man].9. common_noun(n(men),pl) --> [men].10. pronoun(i) --> [i].11. pronoun(we) --> [we].12. pronoun(me) --> [me].13. pp(pp(P,NP)) --> preposition(P), np(NP,_).14. preposition(p(by)) --> [by].15. vp(vp(VP,PP),_) --> vp(VP,_), pp(PP).16. vp(vp(A,V),Number) --> aux(A,Number),

transitive(V,en). 17. vp(vp(Y),_) --> unergative(Y). 18. vp(vp(Y,Z),_) --> transitive(Y,_), np(Z,_).19. unergative(v(ran)) --> [ran].20. transitive(v(hit),_) --> [hit].21. transitive(v(eat),root) --> [eat].22. transitive(v(eats),s) --> [eats].23. transitive(v(ate),ed) --> [ate].24. transitive(v(eaten),en) --> [eaten].25. aux(aux(was),sg) --> [was].26. aux(aux(were),pl) --> [were].

Grammar built in class: Part 1• s(s(Y,Z)) --> np(Y,Num1), vp(Z,Num2), {Num1 = Num2}. % Partial Subject-Verb agreement• np(np(Y),Number) --> pronoun(Y,Number).• np(np(D,N),Number) --> det(D,Number), common_noun(N,Number).• det(det(the),_) --> [the].• det(det(a),sg) --> [a].• common_noun(n(apple),sg) --> [apple].• common_noun(n(ball),sg) --> [ball].• common_noun(n(man),sg) --> [man].• common_noun(n(men),pl) --> [men].• pronoun(i,sg) --> [i].• pronoun(we,pl) --> [we].• pronoun(me,sg) --> [me].• vp(vp(Y),_) --> unergative(Y). • vp(vp(Y,Z),_) --> transitive(Y,_), np(Z,_).• vp(vp(Aux,vp(V,np(trace))),Number) --> aux(Aux,Number), transitive(V,Ending), {Ending = en}. • vp(vp(VP,NP),Number) --> vp(VP,Number), pp(NP).

Grammar built in class: Part 2• unergative(v(ran)) --> [ran].• transitive(v(hit),root) --> [hit].• transitive(v(hit-s),s) --> [hits].• transitive(v(hit-ing),ing) --> [hitting].• transitive(v(hit-ed),ed) --> [hit].• transitive(v(hit-en),en) --> [hit].• transitive(v(eat),root) --> [eat].• transitive(v(eat-ing),ing) --> [eating].• transitive(v(eat-s),s) --> [eats].• transitive(v(eat-ed),ed) --> [ate].• transitive(v(eat-en),en) --> [eaten].• aux(aux(was),sg) --> [was].• aux(aux(was),pl) --> [were].• pp(pp(P,NP)) --> p(P), np(NP,_).• p(p(by)) --> [by].

Outstanding issues

• The relative order of the VP rules is criticale.g. what happens when the rulevp(vp(VP,PP),Number) --> vp(VP,Number), pp(PP).is moved around in the program for the following query?

?- s(X,[the,balls,were,hit,by,me],[]).

• how to block recursion (iteration) for *the balls were hit by me by the man??- s(X,[the,balls,were,hit,by,me,by,the,man],[]).

• would (less linguistically desirable) ternary branching for the VP adjunct work better computationally?e.g. vp(vp(A,V,PP)) --> aux(A), transitive(V,en), pp(PP).

More to come…

• Grammar also has infinite loops,

i.e. does not terminate properly

• We’ll fix these issues next time