Báo cáo khoa học: "RELATING SYNTAX AND SEMANTICS: THE SYNTACTICO-SEMANTIC LEXICON OF THE SYSTEM VIE-LANG" doc

THE s Y N T A C T I C O - S E M A N T I C L E X I C O N OF THE S Y S T E M V I E - L A N G

I n g e b o r g S t e i n a c k e r , E r n s t B u c h b e r g e r

D e p a r t m e n t of M e d i c a l C y b e r n e t i c s

U n i v e r s i t y of V i e n n a , A u s t r i a

A B S T R A C T

T h i s p a p e r d e s c r i b e s the s t r u c t u r e

and e v a l u a t i o n of the s y n t a c t i c o - s e m a n t i c

l e x i c o n (SSL) of the G e r m a n N a t u r a l

L a n g u a g e U n d e r s t a n d i n g S y s t e m V I E - L A N G

[3] V I E - L A N G u s e s an S I - N e t [2] as

i n t e r n a l r e p r e s e n t a t i o n The S S L c o n t a i n s

the r u l e s a c c o r d i n g to w h i c h the m a p p i n g

b e t w e e n n e t - s t r u c t u r e s and s u r f a c e

s t r u c t u r e s of a s e n t e n c e is c a r r i e d out

T h i s i n f o r m a t i o n is s t r u c t u r e d in a w a y

t h a t it c a n be evaluated from two s i d e s

p r o d u c t i o n - r u l e s t h a t c o n t r o l the

a n a l y s i s S y n t a c t i c and s e m a n t i c f e a t u r e s

of the input s e n t e n c e are e v a l u a t e d and

i n d i v i d u a l s a r e c r e a t e d in the s e m a n t i c

net The g e n e r a t o r uses the s a m e r u l e s to

e x p r e s s s e l e c t e d n e t - s t r u c t u r e s in

a d e q u a t e n a t u r a l l a n g u a g e e x p r e s s i o n s It

is s h o w n h o w b o t h p r o c e s s e s c a n m a k e

e f f e c t i v e use of the SSL The d i f f e r e n t

p o s s i b i l i t i e s for e v a l u a t i n g the S S L a r e

e x p l a i n e d and i l l u s t r a t e d by e x a m p l e s

I O V E R V I E W OF THE S Y S T E M V I E - L A N G

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

In the s y s t e m V I E - L A N G real w o r l d

k n o w l e d g e is r e p r e s e n t e d w i t h i n a s e m a n t i c

net (SN) w h i c h is r e a l i z e d in the

f o r m a l i s m of an S I - N e t [2] The net is

o r g a n i z e d in two l a y e r s

The g e n e r i c layer c o n t a i n s the s t a t i c

k n o w l e d g e of the s y s t e m At the g e n e r i c

level real w o r l d k n o w l e d g e is r e p r e s e n t e d

in the form of c o n c e p t s and roles A

c o n c e p t is d e f i n e d by its a t t r i b u t e s w h i c h

c o n s i s t of two p a r t s : role and v a l u e

r e s t r i c t i o n The v a l u e r e s t r i c t i o n is a

c o n c e p t w h i c h d e f i n e s the r a n g e of

p o s s i b l e f i l l e r s for the a t t r i b u t e , the

role d e f i n e s the r e l a t i o n of the f i l l e r to

the c o n c e p t b e i n g d e f i n e d

G e n e r i c c o n c e p t s are o r g a n i z e d in a

h i e r a r c h y of s u p e r - and s u b c o n c e p t s in

w h i c h a s u b c o n c e p t i n h e r i t s all a t t r i b u t e s

of its s u p e r c o n c e p t s The s e c o n d layer of the n e t c o n t a i n s the d y n a m i c k n o w l e d g e w h i c h c o n s i s t s of

i n d i v i d u a l i z e d c o n c e p t s The p a r s e r

c r e a t e s i n d i v i d u a l s of t h o s e n e t

s t r u c t u r e s w h i c h are a d d r e s s e d by the input w o r d s As m o r e input is a n a l y z e d

m o r e i n d i v i d u a l s and links a r e c r e a t e d

T h e s e i n d i v i d u a l s c o n s t i t u t e the e p i s o d i c

l a y e r of the net

The c o n c e p t u a l c o n t e n t of the n e t is

o r g a n i z e d a c c o r d i n g to the idea o f

s e m a n t i c p r i m i t i v e s [8] w h i c h are

c h a r a c t e r i z e d by t y p i c a l a t t r i b u t e s

A c t i o n p r i m i t i v e s h a v e a t t r i b u t e s w h i c h

c o r r e s p o n d to c a s e s of a c a s e g r a m m a r (AGENT, O B J E C T , R E C I P I E N T , L O C A T I O N , etc.) [4], [ii]

B P a r s i n @ Our p a r s e r b e l o n g s to the c l a s s o f

s e m a n t i c p a r s e r s as s u g g e s t e d by [i], [7]

S i n c e s y n t a x c a r r i e s a lot of i n f o r m a t i o n

in G e r m a n it has to be c o n s i d e r e d in

a n a l y s i s : The s y n t a c t i c role of a

c o n s t i t u e n t c a n n o t be d e t e r m i n e d by

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

e n d i n g s w h i c h i n d i c a t e the s u r f a c e c a s e o f the c o n s t i t u e n t h a v e to be evaluated

The p a r s e r is a d a t a - d r i v e n s y s t e m ,

w h i c h c o m b i n e s s y n t a c t i c and s e m a n t i c

p r o c e s s e s S y n t a x is used as the tool to

g a i n i n f o r m a t i o n c o n c e r n i n g the

c o n s t i t u e n t s of the s e n t e n c e , but the

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

o n e s in o r d e r to c o n f i r m their h y p o t h e s e s

a b o u t a c o n s t i t u e n t To r e c o g n i z e NPs and PPs the p a r s e r u s e s an ATN, w h i c h a c c e p t s

s e m a n t i c a l l y v a l i d i n t e r p r e t a t i o n s o n l y The r e s u l t a n t s t r u c t u r e s i n c l u d e s y n t a c t i c and s e m a n t i c i n f o r m a t i o n a b o u t the

c o n s t i t u e n t T h e s e s t r u c t u r e s a r e then

c o l l e c t e d in a c o n s t i t u e n t list

The s e m a n t i c r e p r e s e n t a t i o n of a

s e n t e n c e is b u i l t by l i n k i n g the

c o n s t i t u e n t s to the p r e d i c a t e T h i s

p r o c e s s is c o n t r o l l e d by the S S L - e n t r y for

the v e r b F i r s t the d o m i n a n t v e r b has to

be d i s a m b i g u a t e d [9] S S L e n t r i e s for

v e r b s c o n t a i n the i n f o r m a t i o n h o w

v e r b - d e p e n d e n t c o n s t i t u e n t s are m a p p e d

onto the c a s e s r e p r e s e n t e d w i t h i n the net

In a last s t e p r e f e r e n t s for m o d i f y i n g

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

A s e n t e n c e is c o n s i d e r e d to h a v e b e e n

p a r s e d s u c c e s s f u l l y a f t e r all c o n s t i t u e n t s

of the s e n t e n c e h a v e b e e n i n c o r p o r a t e d

As a r e s u l t the p a r s e r p r o d u c e s a

c o n f i g u r a t i o n of i n d i v i d u a l s in the n e t -

the s e m a n t i c r e p r e s e n t a t i o n of the input

C G e n e r a t i o n

The task of the g e n e r a t o r is to

c o n v e r t a s e l e c t e d part of the e p i s o d i c

layer of the s e m a n t i c net into s u r f a c e

s e n t e n c e s T h i s p a r t - a root n o d e and

v e r t i c e s and n o d e s a t t a c h e d to it form a

c o h e r e n t g r a p h - is a s s u m e d to h a v e b e e n

d e t e r m i n e d p r e v i o u s l y by the d i a l o g u e

c o m p o n e n t G e n e r a t i o n is a c c o m p l i s h e d in

two steps: s t e p o n e p e r f o r m s a m a p p i n g of

the SN to an i n t e r m e d i a t e s t r u c t u r e (IMS)

c o n t a i n i n g w o r d s t o g e t h e r w i t h s y n t a c t i c a l

and m o r p h o l o g i c a l data, and s t e p two

t r a n s f o r m s the IMS to s u r f a c e s e n t e n c e s by

a p p l y i n g s y n t a c t i c a l t r a n s f o r m a t i o n s ,

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

s y n t h e s i s

To p r o d u c e a s i n g l e s e n t e n c e , the

d o m i n a t i n g v e r b is s e l e c t e d first, as it

p l a y s a c e n t r a l role in a s e n t e n c e The

s e m a n t i c p r i m i t i v e s of w h i c h the SN is

c o m p o s e d i m p l y that there is no o n e - t o - o n e

c o r r e s p o n d e n c e b e t w e e n c o n c e p t s in the n e t

and w o r d s of the l a n g u a g e T h e r e f o r e the

d e c i s i o n w h i c h v e r b to s e l e c t d e p e n d s on

the p a t t e r n of i n d i v i d u a l s in the e p i s o d i c

layer of the net The c r i t e r i a for this

s e l e c t i o n are a t t a c h e d to the g e n e r i c

c o n c e p t of the root n o d e in form of a

d i s c r i m i n a t i o n net (DN) [5] Its t e s t s

e v a l u a t e the filled a t t r i b u t e s of the root

p r i m i t i v e The e v a l u a t i o n of t h i s DN

r e s u l t s not o n l y in a verb, but in a

v e r b - s e n s e

The g e n e r a t o r a c c e s s e s the S S L e n t r y

for this v e r b - s e n s e and c o n t i n u e s by

p r o c e s s i n g the d i f f e r e n t r u l e s of w h i c h it

is c o m p o s e d The r u l e s are e v a l u a t e d from

right to left R i g h t s i d e s m a i n l y deal

w i t h e n t i t i e s in the SN, e s p e c i a l l y

i n d i v i d u a l s If an i n d i v i d u a l is r e l e v a n t

to g e n e r a t i o n , it is put on a s t a c k

( " c u r r e n t individual") W h e n the left

side is p r o c e s s e d , s y n t a c t i c a l d a t a a l o n g

w i t h the r e s u l t of a r e c u r s i v e call of

this part of the g e n e r a t o r is p a s s e d to

a r g u m e n t of t h i s call) is t h e n r e m o v e d from the s t a c k and c o n t r o l is r e t u r n e d to the c a l l i n g p r o c e d u r e , thus a l l o w i n g the

n e x t rule to be p r o c e s s e d The IMS w h i c h

is c r e a t e d d u r i n g this p a r t of the p r o c e s s

f o r m s the input for the s t e p two p r o c e s s o r

w h i c h w i l l f i n a l l y p r o d u c e the o u t p u t

s e n t e n c e [6]

II T H E S Y N T A C T I C O - S E M A N T I C L E X I C O N

By m e a n s of the S S L the m a p p i n g

b e t w e e n s u r f a c e e x p r e s s i o n s in n a t u r a l

l a n g u a g e and s t r u c t u r e s of the

r e p r e s e n t a t i o n is a c h i e v e d For an N L U

d i a l o g u e s y s t e m the r e l a t i o n b e t w e e n

s u r f a c e and r e p r e s e n t a t i o n is of i n t e r e s t

in the c o n t e x t of p a r s i n g and the c o n t e x t

of g e n e r a t i n g The s t r u c t u r e of the S S L

a l l o w s i n t e r p r e t a t i o n by b o t h p r o c e s s e s

A t t r i b u t e s of a c t i o n s r e a l i z e the ideas of a case g r a m m a r T h i s l e a d s to a

c o r r e s p o n d e n c e b e t w e e n roles in the net and s u r f a c e c a s e s w i t h i n the s e n t e n c e

C a s e s of a c a s e g r a m m a r at the o n e hand

s h o w r e g u l a r i t i e s in their r e l a t i o n to

s y n t a c t i c c o n s t i t u e n t s ( s u b j e c t -> A G E N T ) ,

at the o t h e r h a n d the r e l a t i o n b e t w e e n a role and a s u r f a c e case is v e r b - d e p e n d e n t E.g the v e r b ' b e k o m m e n ' (to get) r e l a t e s the s u b j e c t to the role R E C I P I E N T , the

v e r b 'geben' (to give) r e l a t e s the s u b j e c t

to the r o l e S O U R C E The v e r b 'geben'

r e q u i r e s the R E C I P I E N T to be e x p r e s s e d by

a d a t i v e Such d e p e n d e n c i e s are c a p t u r e d

in the e n t r i e s of the SSL w h e r e a s the

r e g u l a r i t i e s are t r e a t e d by d e f a u l t s

A S t r u c t u r e of the SSL The b a s i c unit in the SSL is the

e n t r y for a w o r d - s e n s e A s s o c i a t e d to

e a c h w o r d - s e n s e is an o p t i o n a l n u m b e r of

p a i r s w h i c h we will d e s c r i b e by the t e r m s 'Left Side' (LS) and 'Right Side' (RS) A

p a i r d e s c r i b e s h o w a word (phrase) of the

s e n t e n c e is r e p r e s e n t e d w i t h i n the

s e m a n t i c net

LSs d e s c r i b e f e a t u r e s of the s u r f a c e

s e n t e n c e M o s t f e a t u r e s r e f e r to

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

of a g i v e n s u r f a c e c a s e , i n f i n i t i v e

c o n s t r u c t i o n s , l e x i c a l c a t e g o r i e s , s u r f a c e

w o r d s , a n d some f e a t u r e s i n d i c a t e

s e l e c t i o n a l r e s t r i c t i o n s If a LS

c o n t a i n s m o r e than one f e a t u r e t h e y a r e

c o m b i n e d w i t h an o p e r a t o r One o f the

m o s t f r e q u e n t p a t t e r n s that is used in LSs

c o m b i n e s a s y n t a c t i c f e a t u r e w i t h a net

c o n c e p t w h i c h is i n t e r p r e t e d as

s e l e c t i o n a l r e s t r i c t i o n T h i s c o m b i n a t i o n

r e f l e c t s our g e n e r a l p a r s i n g a p p r o a c h to

c o m b i n e s y n t a x w i t h s e m a n t i c s

RSs r e f e r m o s t l y to s t r u c t u r e s w i t h i n

the s e m a n t i c net T h e r e is no o n e - t o - o n e

c o r r e s p o n d e n c e b e t w e e n w o r d - s e n s e s and

c o n c e p t u a l p r i m i t i v e s To r e p r e s e n t w o r d

(or phrase) m e a n i n g s p r i m i t i v e s a r e l i n k e d

f o r m i n g m o r e c o m p l e x s t r u c t u r e s By

d e f i n i t i o n t h e r e is o n e d i s t i n g u i s h e d

c o n c e p t in e a c h RS 'the r o o t c o n c e p t '

w h i c h is the c e n t r a l e l e m e n t o f the

r e p r e s e n t a t i o n All o t h e r s t r u c t u r e s

r e f e r e n c e d in an RS a r e l i n k e d to it

a c t i o n - p r i m i t i v e s is r e l a t i v e l y s m a l l

(14), the n e t p r o v i d e s p o s s i b i l i t i e s to

e x p r e s s d i f f e r e n c e s b e t w e e n r e l a t e d v e r b s

T h i s is d o n e by f i l l i n g a t t r i b u t e s w i t h

c e r t a i n v a l u e s b y d e f a u l t S u c h an

a t t r i b u t e d o e s n o t c o r r e s p o n d to a

c o n s t i t u e n t of the s e n t e n c e but is 'part'

of the v e r b - s e n s e , e,g 'gehen' (to go)

is r e p r e s e n t e d by the c o n c e p t

C H A N G E OF L O C A T I O N , 'laufen' (to run)

a d d r e s S e s - t h e s a m e c o n c e p t , but its

a t t r i b u t e S P E E D is filled by a d i f f e r e n t

v a l u e

N o t all S S L e n t r i e s are r e l e v a n t to

p a r s e r and g e n e r a t o r - some e n t r i e s are

r e l e v a n t to o n e p r o c e s s o n l y T h i s s h o u l d

not be r e g a r d e d as a disadvantage, o n the

c o n t r a r y , s u c h e n t r i e s s u p p o r t e f f i c i e n t

use of the SSL S i n c e e a c h s u b s y s t e m has

its o w n t y p i c a l w a y of i n t e r p r e t i n g

e n t r i e s (LS and RS), p r o c e s s - s p e c i f i c

e n t r i e s are s i m p l y d i s r e g a r d e d by the

o t h e r s y s t e m

B E v a l u a t i o n of the S S L

P a r s e r and g e n e r a t o r t r e a t the

e n t r i e s in the S S L as p r o d u c t i o n - r u l e s ,

e a c h i n t e r p r e t i n g LS and RS in its o w n

way The p a r s e r w o r k s from LSs to RSs

w h e r e a s the g e n e r a t o r w o r k s in the

o p p o s i t e d i r e c t i o n

i P a r s i n @

The p a r s e r n e e d s to m a p

s u r f a c e - c o n s t i t u e n t s o n t o e l e m e n t s of the

s e m a n t i c net To p r o d u c e the s e m a n t i c

r e p r e s e n t a t i o n of an input w o r d the p a r s e r

a c c e s s e s the SSL e n t r y of t h i s w o r d For

e a c h w o r d t h e r e m a y be s e v e r a l w o r d - s e n s e

e n t r i e s The LSs of all w o r d - s e n s e

e n t r i e s for a word i n c o r p o r a t e the

i n f o r m a t i o n n e c e s s a r y to d i s t i n g u i s h o n e

sense from the o t h e r s The p a r s e r

i n t e r p r e t s the LSs as c o n d i t i o n s t h a t h a v e

to be f u l f i l l e d by the input s e n t e n c e

The S S L c o n t a i n s at least o n e pair LS - RS

for e a c h w o r d - s e n s e In o r d e r to c h o o s e

the c o r r e c t i n t e r p r e t a t i o n the LSs of the

d i f f e r e n t w o r d - s e n s e s are e v a l u a t e d

A f t e r the p a r s e r has c h o s e n a w o r d - s e n s e

by m a t c h i n g s e n t e n c e - p a t t e r n s and

L S - c o n d i t i o n s the a s s o c i a t e d RSs a r e

s e q u e n t i a l l y For the p a r s e r the

s t r u c t u r e s in the RS a r e i n t e r p r e t e d as

r e p r e s e n t a t i o n of the w o r d , t h e r e f o r e the

i n d i c a t e d n e t - s t r u c t u r e s a r e

i n d i v i d u a l i z e d The c o m p l e t e s t r u c t u r e

t h a t has b e e n c r e a t e d a f t e r all RSs h a v e

r e p r e s e n t a t i o n of the i n p u t - w o r d

V e r b - e n t r i e s for e x a m p l e s p e c i f y the r e l a t i o n b e t w e e n s u r f a c e c o n s t i t u e n t s and the c a s e s w h i c h a r e a t t r i b u t e s o f the

a c t i o n c o n c e p t E a c h v e r b - s e n s e c a l l s for

a t y p i c a l s e n t e n t i a l p a t t e r n in w h i c h e a c h

c o n s t i t u e n t h a s to fulfil c e r t a i n s e m a n t i c

r e s t r i c t i o n s The p a r s e r s e l e c t s a

v e r b - s e n s e if the f e a t u r e s of c o n s t i t u e n t s

in the c o n s t i t u e n t list s a t i s f y the

c o n d i t i o n s of the LSs A f t e r h a v i n g

s e l e c t e d one w o r d - s e n s e its RSs a r e

e v a l u a t e d and the c o n s t i t u e n t s are l i n k e d

to the a c t i o n as c a s e - f i l l e r s

The p a r s e r uses the S S L e n t r i e s

to d i s a m b i g u a t e v e r b s The LSs

i n c o r p o r a t e the f a c t o r s b y w h i c h

w o r d - s e n s e s can be d i s c r i m i n a t e d f r o m e a c h

o t h e r For m a n y v e r b s the s e l e c t i o n a l

r e s t r i c t i o n of the d i r e c t o b j e c t is a

d e c i s i v e f a c t o r E.g the v e r b ' b e k o m m e n ' (to get) is i n t e r p r e t e d as

O B J T R A N S iff the s e m a n t i c r e s t r i c t i o n o f the d i r e c t o b j e c t b e l o n g s to the c l a s s

O W N A B L E - O B J E C T (see Fig i) The

m e c h a n i s m s by w h i c h d i s a m b i g u a t i o n is

c a r r i e d out if the LS is n o t m e t is

e x p l a i n e d e l s e w h e r e [10]

( B E K O M M E N (i [(AND (CASE ACC) (RESTR O W N A B L E - O B J E C T ) ) ((IND O B J T R A N S )

(VAL + O B J E C T *))]

[ (T (CASE NOM)) >

((VAL + R E C I P I E N T *))]

[(AND (PP VON) (RESTR P E R S O N I N S T I T U T I O N ) ) ((VAL + S O U R C E *))]))

Fig 1

S S L e n t r y for ' b e k o m m e n ' , w o r d - s e n s e - i

('to g e t an o b j e c t ' )

W h e n the p a r s e r a n a l y s e s the

s e n t e n c e 'Hans b e k o m m t v o n d i e s e r F r a u ein Buch.' (John g e t s a b o o k f r o m t h i s w o m a n )

t h e r e are t h r e e c o n s t i t u e n t s on the

c o n s t i t u e n t list

I n t e r p r e t a t i o n of the f i r s t pair

of the e n t r y for b e k o m m e n - i l e a d s to the

i n s t a n t i a t i o n of the root c o n c e p t O B J T R A N S

(RS: (IND O B J T R A N S ) ) and the c r e a t i o n of

the v a l u e O B J E C T f i l l e d by the

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

The p a r a m e t e r '+' r e f e r s to the

root i n d i v i d u a l f o r all p a i r s o f the

w o r d - s e n s e entry For the p a r s e r the

p a r a m e t e r '*' in the S S L r e f e r s to the

r e p r e s e n t a t i o n of the c o n s t i t u e n t s e l e c t e d

by the LS w h i c h is local to o n e pair

The s e c o n d pair l e a d s to the

i n s t a n t i a t i o n of the v a l u e R E C I P I E N T

f i l l e d by the r e p r e s e n t a t i o n for 'Hans'

and the third one f i n a l l y i n s t a n t i a t e s

S O U R C E f i l l e d by the r e p r e s e n t a t i o n of

'Frau' The r e s u l t i n g r e p r e s e n t a t i o n of

the s e n t e n c e is s h o w n in Fig 2

/ ~ r e c i p i e n t

name

Fig 2

N e t s t r u c t u r e for

'Hans b e k o m m t y o n d i e s e r Frau ein Buch.'

A c t i o n p r i m i t i v e s t y p i c a l l y h a v e

an A G E N T and an O B J E C T a t t r i b u t e In m o s t

c a s e s t h e i r s u r f a c e e q u i v a l e n t s are

s u b j e c t and d i r e c t o b j e c t r e s p e c t i v e l y

T h e r e f o r e it w o u l d be r e d u n d a n t to i n c l u d e

these r e l a t i o n s for e v e r y verb In these

c a s e s o n l y the root c o n c e p t is g i v e n in

the RS (see Fig 3) The m a p p i n g is

c a r r i e d out b y d e f a u l t m e c h a n i s m s w h i c h

are a p p l i e d w h e n e v e r the LSs do not r e f e r

to s u b j e c t or d i r e c t o b j e c t

(ESSEN

(i

[(T) - - > ( ( I N D I N G E S T ) ) ] ) )

Fig 3

S S L e n t r y for 'essen' , w o r d - s e n s e - i

('to eat')

s e l e c t i o n a l r e s t r i c t i o n s a r e c h e c k e d

i m p l i c i t l y The net d o e s n o t a l l o w

i n s t a n t i a t i o n of s t r u c t u r e s t h a t do not

c o r r e s p o n d to the p a t t e r n s g i v e n in the

g e n e r i c c o n c e p t s If t h i s o c c u r s e.g in the s e n t e n c e 'He will eat his hat.' an

e r r o r - m e s s a g e is g e n e r a t e d b e c a u s e the

s e m a n t i c c o n c e p t for 'hat', G A R M E N T , is not c o m p a t i b l e w i t h the r e s t r i c t i o n

S U B S T A N C E for the O B J E C T of the c o n c e p t INGEST At t h i s s t a g e of d e v e l o p m e n t we

do not l o o s e n s e l e c t i o n a l r e s t r i c t i o n s as

s u g g e s t e d by W i l k ' s p r e f e r e n c e s e m a n t i c s [12]

2 G e n e r a t o r

W h e n g e n e r a t i n g a s e n t e n c e , the

g e n e r a t o r s t a r t s b y r e g a r d i n g the r o o t

n o d e w h i c h h a s b e e n p a s s e d to it b y the

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

n o d e w i l l , t o g e t h e r w i t h the a t t r i b u t e s

a t t a c h e d to it, c o r r e s p o n d to a v e r b , so this v e r b is s e l e c t e d first As m e n t i o n e d

a b o v e , a d i s c r i m i n a t i o n net is used to

a c c o m p l i s h t h i s task The DN s e l e c t s a

v e r b - s e n s e a c c o r d i n g to the a t t r i b u t e s of the root n o d e

We w i l l s h o w the f u r t h e r

p r o c e s s i n g by m e a n s of the e x a m p l e s h o w n

in Fig 2 Let us a s s u m e the v e r b - s e n s e 1

a l r e a d y b e e n s e l e c t e d The e n t r i e s of the

S S L a r e t r e a t e d from right to left b y the

g e n e r a t o r , so we s t a r t w i t h (IND

O B J T R A N S ) T h i s w i l l r e s u l t in a null

a c t i o n for the g e n e r a t o r , as an i n s t a n c e

of O B J T R A N S ( O B J T R A N S - I I ) is a l r e a d y k n o w n

as c u r r e n t r o o t n o d e and it h a s b e e n put

as f i r s t e l e m e n t o n t o the s t a c k for the

c u r r e n t i n d i v i d u a l (VAL + O B J E C T *) is

c o n s i d e r e d next + d e n o t e s the root n o d e ,

* the~ i n d i v i d u a l a t t a c h e d to that r o l e of

it w h i c h is s p e c i f i e d by the s e c o n d

p a r a m e t e r , i.e OBJECT T h i s e l e m e n t ,

n a m e l y B O O K - 4 , is put on the stack

N o w the g e n e r a t o r p r o c e e d s w i t h the LS: (CASE ACC) is a r e c u r s i v e call to the g e n e r a t o r w i t h the c u r r e n t i n d i v i d u a l ,

B O O K - 4 , as n e w root n o d e t o g e t h e r w i t h the

i n f o r m a t i o n that the r e s u l t shall bear

a c c u s a t i v e c a s e e n d i n g s The g e n e r a t o r

p r o c e s s e s the DN for the c o n c e p t 'BOOK' and r e t u r n s 'Buch' T h i s l e x e m e t o g e t h e r

w i t h the c a s e i n f o r m a t i o n n o w f o r m s p a r t

of the IMS A f t e r h a v i n g p r o c e s s e d the

c u r r e n t i n d i v i d u a l B O O K - 4 , it is r e m o v e d

O W N A B L E O B J E C T ) r e s u l t s in a n o - o p for the

g e n e r a t ~ r , as t h i s i n f o r m a t i o n has a l r e a d y

b e e n p r o c e s s e d in the DN w h e n d e c i d i n g to use the v e r b - s e n s e ' b e k o m m e n - l ' (see

b e l o w )

The s e c o n d R S - L S - p a i r is t r e a t e d

in a s i m i l a r way: The i n d i v i d u a l a t t a c h e d

99

NOM) c a l l s the g e n e r a t o r w i t h P E R S O N - 9 as

n e w r o o t n o d e and says that the r e s u l t a n t

s t r u c t u r e s h a l l be r e n d e r e d as a

n o m i n a t i v e The DN of P E R S O N s u p p l i e s the

i n f o r m a t i o n that p e r s o n s a r e b e s t

s p e c i f i e d by t h e i r n a m e s (if p r e s e n t in

the n e t - if n o t , o t h e r c r i t e r i a are

c o n s i d e r e d ) , and so the w o r d 'Hans'

c o m p l e t e s the s t r u c t u r e b e i n g p a s s e d to

the IMS

t e s t - a c t i o n - p a i r , Pp c a u s e s a

p r e p o s i t i o n a l p h r a s e , 'yon der F r a u ' , to

be c r e a t e d In G e r m a n , the p r e p o s i t i o n

'yon' i m p l i e s d a t i v e c a s e , so no

a d d i t i o n a l e n t r y (CASE DAT) is r e q u i r e d in

the SSL (Note that this o m i s s i o n e n a b l e s

the p a r s e r to i g n o r e c a s e e r r o r s in the

input s e n t e n c e that do not i n f l u e n c e the

s e m a n t i c s )

3 C r e a t i n g D i s c r i m i n a t i o n N e t s

So far, the use of the S S L h a s

b e e n d e m o n s t r a t e d o n l y p a r t i a l l y : in the

e x a m p l e a b o v e s o m e o f the e l e m e n t s in RSs

and LSs h a v e b e e n t r e a t e d as n o - o p s ,

e s p e c i a l l y I N D I V and RESTR T h e s e

e l e m e n t s , i n s t e a d of b e i n g used in the

p r o c e s s of g e n e r a t i o n , p r o v i d e i n f o r m a t i o n

for b u i l d i n g data s t r u c t u r e s for the

g e n e r a t o r , n a m e l y the a b o v e m e n t i o n e d DNs

AS an e x a m p l e , c o n s i d e r the

e n t r y for ' b e k o m m e n ' (Fig i), ( I N D I V

O B J T R A N S ) i n f o r m s us a b o u t a

c o r r e s p o n d e n c e b e t w e e n the c o n c e p t

O B J T R A N S and the v e r b - s e n s e ' b e k o m m e n - l '

T h i s c o r r e s p o n d e n c e l e a d s to the

i n c o r p o r a t i o n of ' b e k o m m e n - l ' as a l e a f

n o d e in the DN for the c o n c e p t O B J T R A N S

O t h e r c l u e s for c o n s t r u c t i n g the DNs a r e

p r o v i d e d by the VALs, thus g i v i n g t h e m a

d o u b l e usage: (VAL + R E C I P I E N T *) in the

SSL e n t r y for ' b e k o m m e n - l ' (Fig i)

i m p l i e s t h a t an i n d i v i d u a l a t t a c h e d to the

R E C I P I E N T role of an O B J T R A N S i n d i v i d u a l

is a p r e r e q u i s i t e for s e l e c t i n g this

v e r b - s e n s e (The a b s e n c e of a r e c i p i e n t

in the n e t w o u l d lead to the s e l e c t i o n of

' w e g g e b e n ' (to g i v e away).)

III S U M M A R Y

We h a v e s h o w n h o w a l e x i c o n that

i n c l u d e s s y n t a c t i c and s e m a n t i c

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

e f f i c i e n t use by two p r o c e s s e s , p a r s e r and

g e n e r a t o r W h e r e a s b o t h m u s t h a v e a c c e s s

to k n o w l e d g e a b o u t s y n t a x as well as

r e p r e s e n t a t i o n , t h e i r s t a r t i n g p o s i t i o n

d i f f e r s : The p a r s e r is c o n f r o n t e d w i t h

s u r f a c e e x p r e s s i o n s , t h e r e f o r e LSs a r e

e v a l u a t e d first The g e n e r a t o r has to

p r o c e s s n e t s t r u c t u r e s , so it b e g i n s b y

evaluating RSs The r e c i p r o c a l r e l a t i o n

b e t w e e n a n a l y s i s and s y n t h e s i s is r e a l i z e d

in the SSL b y p a i r i n g off LSs and RSs

F l e x i b i l i t y is i n s u r e d by the f a c t t h a t

p a r s e r as w e l l as g e n e r a t o r t r e a t LS and

RS e a c h in an i d i o s y n c r a t i c way

A C K N O W L E D G E M E N T S

T h i s r e s e a r c h w a s s p o n s o r e d by the

A u s t r i a n ' F o n d s zur F o e r d e r u n g der

w i s s e n s c h a f t l i c h e n F o r s c h u n g ' , g r a n t no

4 1 5 8 ( s u p e r v i s i o n R o b e r t T r a p p l )

R E F E R E N C E S

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