System Integration and Control in a Speech Understanding System

American journd

of

Computational

Linguistics

Microfiche 3 4 : 5

W I L L I A M H , P A X T O N AND ANN E R O B I N S O N A r t i f i c i a l I n t e l l i g e n c e C e n t e r

S t a n f o y d R e s e a r c h I n s t i t u t e Menlo Park, C a l i f o r n i a 9 4 0 2 5

ABSTRACT

T w o i m p a r t a n t P r o b l a q 8 i n S p e e c h u n d e r s t a n d i q g a r c haw t o

a f t e o t l v t l y i n t e g r a t e multiple & o u r c t s o f K ~ o w 1 e d g . e w i t h i n t h e

8 Y S t t m and haw t a

c o n t r o l

t h t ! ~ c t l v l t l e s sE t D e S Y e t e ~ t o a r r i v e

a t a p p r o p r i r t a L n t e t p r e t a t L b n r t o r u t t c r s n c e s , T h i r p a p e r f i r s t

d @ & c r l b c 8 t h e

r o l e s

p l r y t d b y a c o u s t i c s , s p n t e r , ~ c c a n t l q s , a n d

d l I c O U T 8 e 1 and S h o w s haw a lanQuaOa d e f i n i t i o n i s Used t o l n t e g r r t c t h c r l n t a a r y s t e n i n a w a y t h a t a l l o w s t h e

interactienr

' t o b e e a s i l y v i r i a l t t T h e s e c o n d p a r t o f t h e p a p e r

d e r c t l b e r an e x t e u t i v t t h a t u c a ~ i n t o r m a f ion f r o m t h e r e k n o w l e d g e 8 a u r c t r

in

i t s c o n t r o l s t r a t e g y ,

A c k n o w l e d g m e n t

A S p e e c h u n d e r o t a n d l n g s y s t e m m u s e u s e many k i n d 5 O f

k n ~ w l c d g @ r e a c h P l a y i n g a p a r t i c u l a r r o l e -elurlmsg t h e

i n t e r p r c t a t l e n sf a n u t t e r a n c e , # h i l e t h e d e r o l c r j a r e

i n t c r r c l a t a d , i t I s l m p o r t a n t t o o c a g l e t o s e p a r a t e t h e

k n 0 w I e d g e s o u r c e s s o t h a t I n t e r P e l a t l a n s a r c v l s l b b e a n d s o t h a t

t h e c a n t r l b u e i s n s f r o m t h e v a r i a u s s Q u r e c s c a n b e s t u d i e d o T h e

k n o w l e d g e s o u r c e s u g e d i n t h t s y s t e m b e l n q d e v c l o ~ e d j o i n t l y b y

SPJ a n d S B C c a n b c c h a r a c t e r i z e d b r o a d l y u n d e r t n s h e a d i n g s o f 8 6 0 ~ 6 t i c ~ ~ s y n t a x I s e m a n t l c s p a n d Q i s c Q u s s e ( w s l k c r ? t a l Q p 1 9 9 5 1

P a b l n b a n , 1 8 7 5 3 H e n d r l x , 1 9 7 5 1 D e u t g c h , 19758 loc cum, 1 9 7 5 1

P i t e a , 1 9 7 5 1 ,

T h c a c o u s t i c c o m p o n e n t r e l a t e s 1 f - n q u 1 ~ t b c @ n F i t h e ~ ( ' # ~ r d $

a n d p h r a s e s ) t o t h e s ~ g c c h w a v e f s t ~ , An a c s u s ~ % c - ~ h o n @ t $ c

p r o c e s s o r e n a l y z c s t n c d i g i t i z e d w a v e f o r m t~ e x t r a c t p a r a m c t c r j

b a s e d o n S p c c e h ~ r ~ d U @ t l ~ n c h a r a c t e r i s t i c s a T h e D a r a m e t e f s

i h c l u d c f u n d a m e n t a b L g e q u e n c y ~ v o l e i n 3 L a b e l o f Q r f l & n t f r e q u e n c y p

e n e r g y d a t a , a n d a t h e r s , F o l l o w i n Q p a r a m e t e r l z a t l a n , v a r i s ~ u s

r u l e s @ a @ ~ p p b t a r d t o g e p a ~ r a t c B P I a c 0 ~ 3 t f . c f e a t u r e d ~ 5 e ~ : l ~ t i ~ n o f

t h e u t t c r a n c t , T h e p a r a m e t e r 6 a n d k s a t u r e s a r e ~ u b s @ q u e n ? l y u s e d

b y t h e L a x l c e l m~plpiglca p r o c c d i a z a , he m a p p @ r 1 s c a l l e d fILarhci

t h e p a r s i n g o f an u t t e r a n c e t o q $ v e a. d e e d ~ i c s n s c o r e a s t o

w h e t h e r a p r o g o r e d word o r p h r a s e c o u l d a c t l ~ a l l y h e p r q a e n t i n t~

s P a c i f I c d t i m e r e g i o n ka l % P A C I n p u t , P h o n o l o q l c a l ~ n d

& ~ a ~ s t l e = p h b n ~ t l t r u l e s a r e u s e d b y t h e m a p p e r t o r ~ l q t ~ n h o n s t t c

S y n t u p r o v i d e s r c l i r b l c ~ r e a s o n a b l y i n c x p e n l i v ~ l n d l c a t l a n r

o f i k l e h words o r g r o u p s of w o r d s m a y c a ~ b i n e a n d o f h o * x c i l

t h t y f i t , S y n t a c t i c r u l e r p l v e g e n e r a l p s t t r r n s f o r c o n r t r u c t l n g

n o u n p h r a s e r , c l a u s t r r a n d s c n t e n c g s a ? d ~ r o ~ i d e c e n s l s t e n c y

eRccks t o r s u c h i t e r r a s nurrber a g r e e m e n t , I n t e s t l r : q w o r d or

P h r a r c c ~ m b i n a t i 6 n S t s y n t a c t i c I n f a r m a t i o r ? a l o n e c a n o f t e n r u l e

O u t a c a n d i d a t e w i t h o u t t h e I7ecd t o r n o r e c o s t l y s e r a n t i c a n a

d t t c o u r a c a n a l y S l f i r

T h t s e m r n t l c c o m p o n e n t i n c l u d e s a g e n e r a l p ~ d e l o f - t h e

d o m a i n o f d l g e a u r s e r a n d e s e t o f a 2 g o r i t h v g f o r c a ~ b i n i q g ( o x

t c j c c t l n g l c o n c e p t s i n t h e d o m a i n , F o r t x r m p l c t g i v e n a v e r b a p d

t w o noun p h r a s e r , s e m a n t i c r o u t i n e s c a n b u i l d t h e c o r r e s p o n d i n g

@ctMintie r a l a t i o n b e t w e e n t h e I t e m s i n d i c a t e d b y t h e n o u n

p h r a s e s ,

T h e d f ~ c o u r s e c o m p o n e n t d e a l s w i t h t h e p e l a t t a n s h i p o f t h e

c u r r e n t

u t t e r a n c e

( o r

a p o r t i o n o f L t ) t a t h e d i a l o g c o n t e x t a n d

t a e n t f t i e s

I n

t h e t a s k d s m a i n , D L s c o u r s e f u n c t i o n s U 6 e i n f a r m a t l o n f r o n p r t v i o u s u t t c r a n c a a t o f i l l o u t e l l i p t i c a l

s x p r e s s l o n s a n d t o f i n d r e f e r e n t 8 f a r P r o n o u n s a n d d e r r n i t e n o u n P ~ T L ~ ~ C I I

The Irhguage d e t l n l t i o n is t h e f o e 4 1 p a i n t f o r I n t e g r a t i n g

t h e # @ k n ~ w l ~ d ~ a s o u r c e s , A l a n q u a g e d e f i n i t i o n I n c l u d e s ( 1 ) s e t 8

u s e

deer n o t e x a c t l y

c o r r e s p o n d

to t h e

c o m m o n

u s e ) , The

c a m P o r t t i o n r u b 6 6 i n d i c a t e h o w P h r a s e g C a n b e combined

i n t o

o t i l l

l ~ r g a r p h t a ~ c ~ ~ M e r e ~ ~ @ c ~ s c Z Y ~ a, p h r a r c p I r 4 l t h e r a w o r d

in

t h e i n p u t o x thc r e s u l t o f 8 p p l y l n P a c o m p o s i t i o n r u l e t o constituent p h P e @ c B c Tne r u l e s g i v e t h e L l d t a r P a t t e r n o t

constituents and .rpeclfieations feu c a l c u l a t i n g v a l u e s f o r b a t h t h e a t t r t b u t e l o f t h e t c r u l f l n p Phrase and

i ~ r

f a c t o r s used in

j u d g i n g t h e

r a s u l t ,

f t i t s a t t h e p h r a a ~ l a v e 1 t h a t t h e k n o w l e d g e s o u r c e s a r e t n t r q r a t t d into t h e 8 y s t r m , Thcrc

a r e

t w o a s p e c t s t o t h e ~ O n t f l b u t l D n s t r o m e r e n s o u r c e l t h e v a l u e s d f p r o p e r t i e s o f t h e p h r a h a r c o m p u t e d b y t h e k n o w l e d g e a o u r q e , a n d t n e s a u r c e c 8

a r r @ r r m s n t o f t h e cart6ct:naser o r th1,lo p h r a s e a 8 a n i n t e r p r e t a t i o n

o f t h e i n p o t , T h e r e t w o a o p e c t r a r e r e f l e c t e d

in

t h e a t t r i b u t e

a n d f a c t o r s t a t e m e n t 8 t h a t

,are

a s s o t l a t t d w i t h Bach o f t h e words

a n d Phrase, i n t h e l r h g u a g r d @ t i n i & l o n r T h r a t r f i b u t c s t a t e m e n t s

p r o v i d e l n a t r y e t l o n r for e o m p u t l n q var l o u r p r a p c r t i c c of t h e

Phra*a, T h e r e i n r t r u c t i a h r may

call

W o n a n y o r a l l o f t h e

oaurccs of k n o u l e d u a , ~ s r a x a m p l a _{f o r} a p h f d s e s p a n n i n g a

p a r t i c u l a r r a g m a r i t , a n a e n u s t i c & t t r l b u t a may s p e c i f y t h e ward8

in

t h a t sagrnantl a n

a t t r i b u t e

S u p p l i e d by t h e s y n t a x _{e a n} s P a c l e Y

r

f a r t u r e

r u e h r r t h r v a l c e ( * r e t l v r P or Q g a a o l ~ c C ) ~ an a t t r i b u t a

L b p p l l e d b y

r e m r n t i c r

errn ' I p e c i f y

r

semantic n e t

k d t e r p r e t a t t o n

b u i l t t r o m t h e rernantfcr o f t h e c o n @ t i t u a n t a p a n d _an a t t r i b u t e

r u p p l i e d by the d i e ~ o u r a e componant

c a n i n d i c a t e

a t o f e r c n t or an

P8cfor

s t r t l t l n t n t r

t a l l h o w t o

u.r@

t h e s e a t t r l b u t r r i n

d W m ! t l n i h g t h e l i k e l i h o o d t h a t t h e P h r a r c i t c o r r r e t

$ n t c r p r e t a t l o n o t t h r i n p u t * The r e s u l t o f e o s b l n l n q t h e f a c t o r s

t o r

u

p r r t l c u l & r

p h r i l t 1 e J l c d a r e o r c , T h r u r c of s u c h

g c o r t r

b y t h e e x e c u t i v e

in

d e t e r m l n t n g a v e r a l l i t r a t e q y f l

d e s c r i b e d b t 1 0 ~ 1 Fact098 a r e n o n b i n a r y f t i n c a t h e y c a n h a v e a

range

o f v a l u e r , r L g i d * y e r e

or

'no*

d t ~ i s t ~ n b 6 4 n o t h a v e t c b e

lad@

in

e s r e r s g n g t h e q U a l l t Y o f a P h t . # 8 e e F o r axa@Ple, t h e

cloransre

o f the a c o u r t l c match asy v a r y

@nu

t h i s C B ~b e

r r t l e c t t d 1 t h e c o r r c t P o n d l n g f a c t o r , w e a k e v i d e n c e

from

one

r o u r c e o f k n o w Z t d g c c o u l d l o w e r t h e r c o r a , r hi la s t r o n g e v i d e n c e

f r o m a m t h e r 80urch c w l d c6mpen8ata f o r t h a t a n d a c t u a l l y r a i s e

t h e S C O ~ - 4 ,

In s u m m a t y r a p h t a r e i s 4 e o m p o ~ l t e i n t a r p r a t a t i o n o f a ~ a r t i c u 1 . r p o r t i o n o f

tne

u t t e r r n e i , i n t t g r ~ t i n p c o n t r i b u t L a n s

from

a11 i a l a v a n t k n a w l e d g @

o a u r ~ t ~

r T h i s m e a n 8 t h a t each

p e r t i a n

o t t h e l n p u t

is

l n t t ' r p r e t e d

and e v a l u a t e d b y t h e system

ar fully a @ P 6 0 S f b & ~ r as 800n 4 1 p o ~ ~ l b l e

,

Tne 8 y 8 t w i s n a v c r

f a c e d w i t h t h e problem o f r t X a t l n p ar e o m b l n i n p f r e q m v n t a r y

t h e a r i e r c o n l t t u c t e d I n d e ~ t n d a n t l ~ bY d i f f r ~ r e n t k n o w l r d u s

8eurcl)s~ and

c v r l u a r l a n r

mrdr b y d i f f e r a n t s o u r c e s a r e

L n i r d l r t e l y mrrqcd t o

e ~ n t r o l

and C o O r d l n r t e o v r r @ l l r y a t c m

a c t i v i t y ,

For

Q X I ~ P I C I a8 goon & f

r

d a f i n l r e

n o u n

P h r & I @ i 8

found# t h e a c o u r f i c c o m p o n e n t chcckr t h r

c o r r t t c u l a t l a n

o f t h e

eanrtltuentr,

t h e r y n t r e t i c c o m p o n e n t c h e c k @ f o r a g r ~ e m e n t

i n

r ~ p r a s r n t r t l o n

o f t h e m e a n i n g , a n d t h e d i r e o u r r e component l o o k s

f a r

r

r e f e r e n t ,

T h e f a l l m i n ~ t x @ a p k e l l l u t t t a t Q p haw S e v e r a l k n o w l e d g @

~ b ~ t c e s a t e

u s e d

t o g e t h e r t o h t e t ~ t e t a n d e v a l u a t e p h r a r e e , T h e

Submarine.*

or

' t h e i r

s u b m a r i n a r @

and

t1l;urtrates

t i n t e g r a t i o n

QS

acauotret

r y n t a c t l e ~

r e m a n t i c @

and

d l r c o u r r e

L n f o r m a r f o n ,

R U L E a ~ C I

N P 9 NP d D E T N O M )

8TRfKG 8 A P P E N Q I S T R I N C I B E T ] r ~ T P I N G ( N Q Y ] ) I

N B R

r CfNTCR8ECT(HBR(DET]tM0R[NUM)),

C M U @ G I N T E R B E C T [ C M U (DET) ,CHU ( N O M ) 1,

IEMARTZC6 $EMCA&L(fl$EMMRNP7,SEHANTtCS(NOM]o

M O O O ( D ~ T ) , C C A S ~ ( O ~ T ) ~ ~ N T E R P R E T A T I O N ~ D E T ~ ) ,

DIlCOURSE 8

It

H O O D [ D t T ) EQ VOEC THEN

D I I C A L L ( ~ ~ D I B R W P ~ , $ & M A N ~ : I C S )

ELBY ~ U U N D ~ E P X N E V ,

I M T t R P R E T A T X O N

t IF DI8C0URSE bU H U N D E F I N t D T H E N

D I l C O U R I E

ELSE

SEMIHTXCBt

COIR'T a M A P P E R ( L ~ ~ T W O F D ( D E T ) , V I R ~ T W O R B ~ ~ Q M ) ) ,

N B P 8 IP NULLXWBR] THEN O U T E t b K

b ~ ,

CMU 8 I F

NuLL(cnu1

T H E N O U T e t a E O K ,

6 t M A H T I C 8 + IF NULL(GEMANTIC$).THEN OUT 6 L 8 L O K ,

DXecouPsE

xr

M O Q R ( D E T ) N Q R D E C T H E N O K ELSE

I r N U L L ( D ~ 1 I C O U R L E ) T H E N P O O R ELSE

I Q

A H B I C U O U & ( D I I C O U R ~ C ) T H E N O K ELSE G O O D ?

r r 8 u l t r n t p h r r a l b , which

In

an a c o u s t i c a t t r i . b u t e i n d i c a t i n g t h e

ward8 c a m p o r i ~ g t h i r p h r w e , N B R (nllmber) a n d C M U

( c a ~ n t m m r 8 8 - U n i t ) axe UynZ&ctlc r E t t i b U t g S t a r t h e P h r r a a . e a c h

r t t r l b u t e a o f t h e c o n & t l t u a n r r r he r a v r n t i c r a t t r i b u t e i s a p i e c e o f

s e m a n t i c

n e t t h a t i s c o n s t r u c t e d f r o m t n t r e m a n t l e s o f

t h e c a n r t t t u c n t r b y t h e s t m a n t l e r o u t i n e ( S k M R N P 7 ) a r a o c i a t e d

w l t h t h i s r u l a , I f t h e MOOD a t t - r i b u t a o f t h e D E T c a n ~ t i t u e n t i s

'DEEC, 1 declarative d e t e r m i n e r , t h e n t h e d l s c a u t s e r a u t i n c s

w i l L leak

f o r

a r e f e r e n t

f o r

t h e P h r a s e in t h e d i a l o g c o n t e x t and

8 s r l Q h i t s r a m d n t l c s t r u c t u r e a $ t h e v a l u e of t h e a t t r i b u t e

PXSCOURSE, T h e I N T E R P R E T A T I O N o f t h e p h r a s e 1 6 e f t h e r t h e

r e f e r e n t f o u n d b y d l ~ c ~ u r r t

o r

t h e s e m a n t i c n e t s t r u c t u r e

I n

c a s e

no

direct r e f e r e n c e is f o u n d @

T h e f r c t o i statements u s e t h e s e a t t r i b u t e s i n c a r n p ~ t f n s

c a n t r t b u t i a n r tawardr t h e s e a r a

f o r

t h e P h r a s e , A s h a $ b e e n

a e n t l o n e d ~

t h e r e f c 4 r m p e o f a e c a p t a B l c v a l u e r f o r f a c t o r r ,

Par r i m p l l c i t y , S y m b o l i e v a l u e r a r e u s e d ( V E F Y C O O P , G O O D , OL,

POOR# B A D t and O U T ] ,

Zn

t h e cxamPlt r u l e r t h e r e

a r e

f a c t o r s deterrnlned b y s a e h a f t h e major k n o w l e d g e s o u r c e s , T h e C a A R T

factor

r e f l e c t s rp a c o u s t i c :crt o f t h e c o a r t l c u l a t i o n o f t h e

k a r t w ~ z d o f t h e c l e t ~ ~ m i n t f a n d t h e f i r s t w o r d o f t h e n o m i n a i l

N e R and C M U

a r c

r y n t i c t l c f a c t o r 8 t h a t w i l l e l i m i n a t e t h e p h r a s e

i t e i t h e r a t t r i b u t 4 1% i n e o m p r t l b l c b t t v c c n t h e c o n r t i t u c n t s .

T h e ranantic f a c t o r * i l l r l l m i n a t e t h e P h F r g c i f n o r e m a n t i e

I n t r r p t + t s t l a n c a n b e t a r m u l a t a d , W h i l e t h e c u r r e n t r e m a n t i c

camgonsnt b a t 6 not h r v a a m e t r i c f o r d @ t h r m i n i n g t h e l i k e l i h o o d o f

@n

i n t c r p r e t d b t l o n o t h e r th.n w h e t h e r o r n o t a S e m a n t i c

r s p r e r t n t a t i o n

can

b e b u t i t ,

i t

i r p o s ~ i b l e t o i n t m d u c c a u c h a

trctor i& n o n b i n a r y , ~f t h e determiner 1 s d e c l a r a t i v e , t h e

d l s e o u r s e h&8 t r i e d t o f i n d a r e f e r e n t , I f n o referent War

f a u n d , t h e f a c t o r

is

g i v e n

r

low v a l u e , * P O O R p r b u t t h e p h r a s e is

not

d i a c s r d e d , I f s c v c r r l p o r r l b l s

r e f e r e n t s

were f o u n d , t h e p h F 8 8 e 1 6 k e p t and t h e

s c o r e

i s not lowered because t h e a m b i g u i t y

can

p e r h a g s b e r e s o l v e d l a t e r , I t j u s t o n e r e f e r e n t war f o u n d ,

I t i s taken ao e v i d e n c e t h a t t h e phraoa 1 s a

c o r r e c t

i n t e r p r e t a t i - a n

f o r

t , h a t P o r t t a n o f the U t t e r a n c e a n d t h e factor"

i s g i v e n a h i g h e r value 'GOOR@,

The example d i s c u s e a d i#bOv@ s h o w s h o w t h e l a n g u a ~ , ~

definition s y g t o m c a n b e u s e d t o i n t e g r a t e a v a r i e t y o f k n o w l e d g e

rourccr

in

a W r y t h a t k e e p s t h e c a n t r i b u t l o n r a n d i n t e r a c t i o n s o f

t h e d i t f w e n t s a u t c r r e a r i l y v i s & b l t r Tns t e p r e r c n t a t l o n

c o m ~ l n c r p r o c e d u r a l I n f a t m e t i o n ( i n t h e e x p r t s l i a n a

f o r

c ~ l c u l a t i n g a t t x l b u t t and f a c t o r V a l u e s 1 e n d d e c l a r a t i v e i n f o r r n r t l a n ( i n t h e c o n s t i t u e n t p a t t e r n ) i n a f o r m d e s i g n e d t o

r i m p l i f y t h c task o f w r i t i n g a large! d e f i n i t i o n c o n t a i n i n g many

rules, Howrvrr, b r f o r e f h c r u i c c c a n a c t u a l l y a e U s r d , t h r ~ m u a t

bcs convert c d

t o

a d i t f c r c n t r a p r a o e n r a t i o n d ~ e i g n e d w i t h

a f f i c d e n c y

In

m i n d , T h i s t W h n 8 l a t i 0 n i s d o n a b y s l a n g u a g e

d e f i n i t i o n compile'l:' t h a t

c e m t r u c t r

a n i n t e r n a l r c p r c r e n t a t i o n o f t h e l a n g u a g e d e f i n i t i o n t h a t d e p e n d % in an i n t r i c a t e w a y on

The a x h c u t i v t maker a d i r t l n c ' t l o n between t h o

phrases

b c l n p

b u i l t a n d t h e tarlcr r k q u i r c d t o b u i l d t h e s e p h r a s e s , A d a t a

S t r U e t U r e r c a l l e d t h e

'parre

net', t d p r e e a n t s t h e g r o w i n g

collcctlon

of p h r a s e # , s n d

another

s t r u c t u r e ,

c a l l e d t h e 'task

q U e u t @ , Cnc0de8 t h e

r l t c r n r t l v e

o p e r r t i * n t a v a i l a b l e f o r t a k l n g

another S t e p toward U n d e r s t a n d i n g t h e i n p u t , E a c h e n t t v i n t h e

t a r K queue s p e c l t i e r r

proccdurt

t o be p e r f o r m e d a t a p a r t i c u l a r

locatton

(node)

In

t h e

p a r s e net,

T h e ~e%torrnancc o t such a

p r o c t d ~ ~ C t y p i c a l l y entails b o t h m o d i f y i n g t h e p a r s e

net

a n d

S e h @ d U l L n g

n a w

t a s k 8 t o

makc

f u r t h e r r n o d l t l c a t t o n s , E a c h t a s k

has

r s s o c l ~ t e d

w i t h i t r p r i o r i t y

f o r

pctf"ormlng I t . T h e m e t h o d

f o r determining p r i a r i t i e r i s d e s c r i b e d b e l o w ,

Taskr

can

include

l p a k l n g

f o r

a

n e w w o r d

or

p h r a s e to f i n i s h

an

1ncomBlett

Phraoa

[one

m t s s f n g

s o m e

o f i t r c o n s t i t u t n t s ] and f r y i n g t o u r e

r

word

or

c o m p l e t e d

phrase

in

a l a r g e r

p h r a s e ,

This

men8

t h a t t h e r y r t e m can work b o t h ' t a p

d o w n r

a n d ' b o t t o m

u p e l b t c a U l t i t can l o o k i n a g o a l - d r i v e n manner f o r m l r r i n g

eonstltutnts

o f

h l g h e r l e v e l p h r a i e s t and i t a l t o c a n a c c e p t

word8

from

t h e

aceurtlcr

t o b u l l d i n t o l r r g a r p h r b r c r in r

d a t a - d r i v e n

mannerr

A S

an

exampkc, C O n s i d t t t h e s i m p l e g r a m m a r

S 8 NP VP

VP

F VP NP I V E R B

V E R B

s

awn

I

l a s t

Assume t h a t , t h e word @ t h e y o h a s been7 f o u n d i n i t L a l l y e i t h e r

b y t h e a c o u s t i c s d i r e c t l y

or

as a r e s u l t of c o n f i r m i n g a

D r e d i e t l a n made b y The l a n g u a g e ? e r t n i t L o n , .They4 c o n s t i t u t e s a

c o m p l t t e NP, T h i s NP cah b e g u t i n t o t h e S rule, c a u $ i n g t h e

p a r t i a l l y f i l l e d phsase 'they V P * t o b e a d d e d t o t h e p a r s e n e t , A l r e a d ~ ~ S o m e o f t h e a t t r i b u t e s a n d f a c t o r s _{t o r} t h e S r u l e c a n b e d r t e r m l n e d , and

r

score c o m p u t e d

_{f o r}

t h i s p h r a s e , B u l l d i n g t h i s p a r t i a l phrase l o a d s t o t h e c r e a t i o n o f a ntw task4 t o look

f o r

a

VP f a l l o W L n g t h e hP, That t a s k

in

t u r n l e a d s t o two a l t e r n a t i v e

8 u b t a g K ~ I Laak f o r a VP N P o r l o o k f a r a V E R B , P r i a r L t L r s f a r

b o t h t h e s e t a s k s a r e computed and t h e y a r e p u t on t h e t a $ k queue

t o b e P r o C @ $ S a d r Tho e x e c u t i v e t h e n r e m o v e s t h e n e x t t a s k _{f r o v}

t h e queue and continues,

In

Penepalc d e c l d i n $ w h i c h t a s k t o perform i s o f g r e a t

Importance, b c c a u r e o n l y a s u b s e t o t t h e s c n c d u L e d t a w s w i l l

actUallY Prove

r o

be

neeassarY

t o U n d e r s t a n d t h e i n g u t ; t h e

ethers w i l l b e * f a l s e s t e p s * l e a d i n g t o d e a d a n q s , ~ d e a i l y r i n

d c c l d i n g wh-ich task t o d o 1 t h e e x e c u t i v e w o u l d a l w a y s C h o o s e one

o f t h e n t e c s o a r y f a 8 k s a n d n e v e r t a k e a f a l s e s t e p , The u t t e r a n c e would b a u n d a r r t o a d w i t h t h e u n n e c e s s a r y t a s k s s t i l l

l e f t $h t h e

Queue,

T a a P ~ r g e c h t h i s i d e a l r t h c a c t u a l s y s t e m

m u s t

s p e n d rome

nf

i t s e f f o r t

I n

c h o d a i n g t a s k s , S u c h o f f o r g i s

well spent i f i t p r o d u c c a a net decrease

in

p r o c e s s i n g t i m e , In

o t h e r W o r d r r t h e etticitncY of t h e s y s t e m w i l l b~ 1rnPcoVed b y

d e c i $ i o n n r e g a r d i n g t h e o r d e r i n w h i c h t a s k s a r e p e r f o t m e d , i f

r t t p r t h a t

w a u l d

o t h e r w i s e h s v c been taken, Since a c + o u a t i c

uncertainty

in

$ p a t c h undersfanding makes t n t p o t o n t l a i f o r

rartlng

effort

en

unnecessary

operattons

p a r t i c u l a r l y _{l a r g e ,} t h e

system can a f f o r d t o carry ,out r a t h e r complex c o m p u t a t i o n s

In

d e c i d i n g what t o d o

next

and S t i l l o b t a i n a l a r g e imrovcment i n

overa$l

e f f f c l t n c y . I n t h e

c u r r e n t

system, t h e d e c i s i o n s a r e based

on

t h e rclativt p r i o r i t i e s a s s i g n e d t o t h e v a r l o u s t a s k s

Waiting

In

the queue, Taska ere aSS*oclated w i t h p h t a s e r , a n d

task p z l o r l t i e r l r r q t l y d e p e n d

a n

h o w important t h e s y s t e m f e e l s

i t i s t o

P r o c e s s

t h e P h r a s e ,

In a d d i t i o n t o t h e

s c o r e s

of Phrases, w h i c h c o m b i n e a

variety o f f a c t o r s b u t awe LndePendant o f t h e l a r g e r g e n t e n t i a l

C O n t U t r t h e

system

form8 another arstrsmcnt o f t h e q u a l i t y of

t h e phrase c a l l e d t h e p h r a s e ' v a l u e e , which d e p e n d s o n t h e

context

o f proPoScd

c o m p l e t e

l n t c r ~ r e t r t i o n r f o r t h e e n t i r e

utteratwe,

The p h r a ~ t

value

i s an estimate o f t h e h i g h c a t s c o r e

€ o r e l l

posslbla

intetprrtationr

s p a n n i n g t h e u t t e r a n c e t h a t

I n c l u d e the P h t a S t , The t l t l n a t t 1 8 tzornputcd b y m e a n s a t a

h e u r i s t i c

a t a r c h

o f t h e space a t por.8 l b l e r e n t c n t i a l c o n t e x t s

t l t a b l i l h e d d u r i n g t h c P r e V i Q U S t a r k s P e r t a r m e d b y t h e c x e e u t l v c ,

The ~ ~ 1 6 f i f ~

o f

a t a g k

I s

i n t t i a l l y r u t t o t h e v a l u e o f i t s aSS@cia0cd Phrrstt b u t t h r P r i o r l t y 1 8 l o w c r c d i t t h e t s a r

conflicts

w i t h the c x c c u t f v c @ s

c u o r t n t

' f o c u r of a e t i v i t y " , T h e phrarr V l f u @ t h a t dttcrmln.8 t h e initial p r L o r l t y r e f l e c t 8 an

te)rtlon t o i t s context, b u t i t does not r e f l e c t i t s competition,

I f a P h r a s e h e 8 e h i g h OalUe, o t h e r S i m i l a r P h r a s e s a r e a l s o l i k e l y t o have h i g h v a l b e s , I f values a l o n e d e t e r m i n e d

p r l o r l t l e s , t h e n e v e n a f t e r s u c c e s s f u l l y c o m p l e t i n g a P h r a s e , t h e

s y s t e m w o u l d t e n d t o c a n t l n u t l o o k i n g f o r m i n o r v a r i a t i o n s In t h e

lame area r a t h e r t h a e m o v i n g

on

t o Look f a r ways t o c o n s t r u c t a c g m p l a t e i n t e r p r e t a t t o n , The a f a c u p d f a c t i v i t y c mechanism

p r o v l d t s a way

f o r

p h r a s e s t o i n h i b i t t h e e x e c u t i v e f r o m l o o k i n g

f o r

c b m p t @ l n p p h r a l t s t h a t w o u l d n e c e ~ s a r i l y f c p l a c c them. T h i s

f o c u s i n g 11 b t o u g h g a b o u t b y l a w e x f n q t h a p r i o r i t y o f t a s k s t h a t

l o o k f a r r ~ ~ l a e c m c n t s f o r a n y o f e S e t a t f o c u s ~ h r a s e s ~ / u n t i l

t h e p o t e n t i a l replacement p r a m l s e s t o l c a d t o e a i g n i f l c a n t

irnpravcmcnt in V a l u e f o r t h e f i n a l i n t e r p r e t a t i o n d T h e e f f e c t i s

t o b i a s t h e s x e c u t - i v c t o w a r d b u l l d i n g UP a complete

i n t e r ~ x e t a t l o n u s i n g phrases i n f o c u s r a t h e r t h a n exploring

competing i n t e r p r t t a t i a n s t h a t wauld n o t use f o c u s p h r a s e s , X f t h e focus 8 wrong, t h e attempts t o e x t e n d i t t o a complete

I n t e r p r e t a t i o n w i l l b e unrucceS4fUl. E v e n t u a l l y a t a o k t h a t

e a n f l i c t s w i t h tne r o c u s w i i r D e c a m e t h e h i g h o s t p r ' i d i i t y

c > P e r r t l a n f a r t h e e,xtcutl,vrc t o P s t f a r q in a p l t e o f t h e b i a s 4 9 r i n 8 t I t r A t a r e s u l t t h e f o c u s W i l l b e m o d l f l ~ d s o t h a t i t

I s

consistent

w i t h t,he n e w t a s k , and tha, e x e c u t i v e w l l L t h e n , c a n c e n t r a t e a n urlna t h e r a V l $ e d ssr a z P h r a s e s ,

I n a d d i t i o n t o e a l e u l r t l n q p r i o t l t L e s o f t a s k s o n t h e b a s t a

o f P h r r r t v a l u e 6 a n d focus o f a c t i v i t y 4 t h e e x e c u t i v e m u s t c n r u r c

s

used e t f ~ c t l v e l y ,

T h i s

i r d o n e b y s t r u e t u r i n q t h e p a r s e n e t

and

t h e

t a s k s

t h a t o p e r a t e on it

in

a w r y t h a t b r i n g s t o g e t h e r r e l a t e d a c t f v l t i e r a n d c a o r d i n s t e s t h r m t o t l l m l p c t c d u p l i c a t i o n

o f effort, B y a v o i d i n g d u p L L c r t i o n , the r y t t t m rcduleeb t h e f U

e f f e c t s o f t h e f a l s e s t e p 8 It w i l l i n e v i t a b t y t a K e , W o r k d a n e o n a f a l s e p a t h f r not

n e c e r s e r i l y

w a r t e d r s l n c r i t m a y p r o d u c e a Phrase t h a t

can

b e u s t d

in

soma o t h e r Way, f o r e x a m p l e r a RPiraSe

eonrftucttd

ir p a r t of an u n s u c c e r r f u l s e a r c h f o g ant! t y p e of Sentence may l a t e r appear

in

f h c tlnal i n t e r p r e t a t i o n s S P a r t o f

a d l f i a r e n t kind o f s t n t s n c c e A l S O r f a l s e s t e p s a r c n o t repeated, s i n c e t h e s y s t e m o n l y makes o n e a t t e m p t t o b u i l d a p a r t t e u l a r t y p e o f P h f r s e

Ln

a P % r t l ~ U l ~ t Zoca,tion i n t h e

utterancar

r t g a r d l @ s s a t how m a n y l a r g e r p h r a s e s m i g h t i n c l u d e

i t , M l a t a k t a

are

intvttabls, b u t a t l e a s t t h e o y t t t m w i l l n o t

make tbf &&me rn1~rrre t w g c e i n a n t par$-

Ta SUmwarl~t!, t h e l a n g u a g e d e f i n i t i o n I s d e s i g n e d t o

facilftrre t h e I n t W r r i i ~ n o f m a n y k n o w l e d g e s a ~ t c @ $ r P u l e s in t h e language dtflnftion c d n t a l n a t t t i b u t e s a n d f a c t o r s f r o m a l l o f there

~ o ~ t c e s ,

The a t t r i b u t e s a r e U r t d t a i n d i c a t e

p a r t i t u t a r

p r o p t t t i t l o f p h r a s e s t and f a c t o r s t h e n U r t t h c ~ c a t t r i b u t e s t o

detrrmtnr

t h . # c o r e o f t h e p h r a s e , T h e e x t e r n a l r e p r e l e n t a t i o n

o f t h e language, d e r l g n c d t o r e a s y U 8 t b y p e o p l e , i n c o n v e r t e d b y

a languapc d e f i n i t i o n c o m p i l e r i n t o a n i n t e r n a l r e p r a r e n t r t l o n , d e r l ~ n t d

t o r

e f f i c i e n t use b y t h @ r x e c u t l v r , I n a s t e p b y s t e p

manner,

t h r e m e u t L v c u s e r t h i s information t o c r e a t e , r v r l u r t e ,

o u t taker t h e form o f a s r l g n i n g p r f a r i t i o s t o a l t e r n a t i v e tasks,

P r l a r i t i e ~ r a t l t c t b a t h t h e e x p e c t e d values o f c a m p l t t e

i n t a r p t e t a t i o n 8 t o w a r d Which t h e t a s k w o u l d l a r d a n d t h e r e l a t i o n

o f t h e t a s k t o t h e c u r r e n t f o c u s

o f

a e t l v l t y , Flnallyr t h e

e n t i r e p r o c e s s i s o r g a n i z e d s o t h a t i n f o r m a t i a n g a i n a d In

P e r f o r m i n g e t ~ 6 K 1 6 S h a r e d and r e c o r d t d in r u c h a way t h a t It does not h a v e t o b e t e d f s c o v e r t d ,

R e f e r e n c e s

Deutsch, Barbara G , E s t a b l l s h l n g C o n t e x t i n T a a k m o r l e n t e d

D i m l o g g , P r e s e n t e d a t t h e T h i r t e e n t h Annual M e e t i n g o f t h e A s s o c i a t i o n f o r C o m p u t a t l o n s l L i n u u i r t i c s , B o s t o n , M a s s a c h u s e t t s ,

30 O c t o b e r 1 N o v e m b e r 1 9 7 5 ,

H c n d r l x , G a r y G

,

a e m a n t i e Processing f o r S p e e c h

U n d a r r t e n d i n g

,

Presented a t t h e T h i r t e e n t h A n n u a l M e e t i n g o f

t h e A s s o c i a t i o n f o r C o m p u t e t l ~ n a l L i n Q u i s t i c s r B o s t o n r M a s s Q c h u r e t t f i r 36 O c t o b e r

-

1 f i o V @ m b t ? 1 9 7 5 ,

R i t c a , H, B a r r y , A u t o m a t i c S p e e c h u n d e r s t a n d i n g S y s t e m s , p r o c e e d i n g s , E l e v e n t h Annual I E E E Computer S o c i e t y 6 0 n f e r e n e e ,

Washington, D , C , r 9 - 1 1 S e p t e m b e r 1 9 7 5 (

~ o b i n r o n r Jane J, A T u n e a b l e ~ e r f o r m a n c e Grammar, P r t s r n t e d a t t h e T h i r t e e n t h A n n u a l M e e t i n g o f t h e A r s ~ c i a t i a n f o r

C o m ~ U t r t l , o n a ~ h l n g u l s t l c r , B a o t o n r M a S S a c h U S e t t 6 r 30 O c t o b e r 1

NoVsmbtr 1 9 7 5 ,

S l a c u r , J o n r t h r q , S p e e c h C c n c r a t l o n f r o m S e m a n t i c N e t s , Prerentad a t t h e T h i r t e e n t h _Annual Mt4Btlmg o f t h e A s a b C i a t i o n f o r

~omputation.1 L i n g \ l i r t i c r , e a r , t o n r M a r ~ a c h u a a t ' t r , 30 ~ c t o b c i r a 1

November 1 9 7 5 ,

walker, D o n a l d E,, c t a l , S p e e c h U n d e r a t a n d l n g R ~ s e a r c h ,