A PROLOG Implementation of Lexical Functional Grammar

L e x i c a l f u n c t i o n a l grammar (LFG) i s a n a t t e m p t t o s o l v e p r o b l e m s t h a t a r i s e i n t r a n s f o r m a t i o n a l grammar and A T N f o r m a l i s m s ( B r e s n a n , 1982 ) . A n o t h e r p o w e r f u l f o r m a l i s m f o r d e s c r i b i n g n a t u r a l l anguages f o l l o w s f r o m a method f o r e x p r e s s i n g grammars i n l o g i c , due to Co lmeraue r (1970) and K o w a l s k i (1974) c a l l e d d e f i n i t e c l a u s e grammars (DCG) (War ren , P e r e i r a , 1980 ) . B o t h f o r m a l i s m s a r e a n a t u r a l e x t e n s i o n o f c o n t e x t f r e e grammars (CFG). The a im o f t h i s pape r i s t o show how LFG can be t r a n s l a t e d i n t o DCG t h a t t h e p r o c e d u r a l s e m a n t i c s o f PROLOG p r o v i d e s a n e f f i c i e n t t o o l f o r L F G i m p l e m e n t a t i o n s i n t h a t i t a l l o w s t h e c o n s t r u c t i o n o f f u n c t i o n s t r u c t u r e s ( f s t r u c t u r e s ) d i r e c t l y d u r i n g t h e p a r s i n g p r o c e s s . I . e . i t i s n o t n e c e s s a r y t o have a s e p a r a t e compon e n t w h i c h f i r s t d e r i v e s a s e t o f f u n c t i o n a l equa t i o n s f r o m t h e p a r s e t r e e , and s e c o n d l y g e n e r a t e s a f s t r u c t u r e b y s o l v i n g t h e s e e q u a t i o n s . I . L e x i c a l f u n c t i o n a l grammar LFG c o n s i s t s o f a s t a n d a r d c o n t e x t f r e e grammar (CFG) a n n o t a t e d w i t h f u n c t i o n a l schemata , d e t e r m i n i n g t h e a s s i g n m e n t o f g r a m m a t i c a l f u n c t i o n s t o t h e C F G r u l e s . The c r u c i a l e l e m e n t s o f t h e t h e o r y a r e t h e g r a m m a t i c a l f u n c t i o n s i n v o l v e d b o t h i n t h e r e p r e s e n t a t i o n o f l e x i c a l i t e m s and i n t h e C F G r u l e s . The g r a m m a t i c a l f u n c t i o n s assumed i n Bresnan a r e c l a s s i f i e d i n s u b c a t e g o r i z a b l e ( o r g o v e r n a b l e ) f u n c t i o n s , namely SUBJ, OBJ, 0BJ2 , OBL COMP, XCOMP, and n o n s u b c a t e g o r i z a b l e o n e s , ADJ and XADJ. The s u b c a t e g o r i z a b l e f u n c t i o n s a r e t h e o n l y ones t o w h i c h l e x i c a l i t e m s can make r e f e r e n c e . The r o l e o f t h e g r a m m a t i c a l f u n c t i o n s i n v o l v e d i n t h e f u n c t i o n a l e q u a t i o n s i s t o p r o v i d e a mapping b e t ween s u r f a c e c a t e g o r i a l s t r u c t u r e and s e m a n t i c p r e d i c a t e a rgument s t r u c t u r e . The e n c o d i n g o f f u n c t i o n a s s i g n i n g e q u a t i o n s i n t o t h e CFG i s done a s f o l l o w s : ( i ) l e x i c a l e n t r i e s : a l e x i c a l i t e m i s a s s o c i a t e d w i t h one o r more s e m a n t i c p r e d i c a t e s ( f o r i t s d i s t i n c t senses o r mean ings) t o g e t h e r w i t h t h e i r a rgument l i s t s , w h i c h c o n s i s t s o f t h e s y n t a c t i c a l l y s u b c a t e g o r i z e d f u n c t i o n s o f t h e l e x i c a l f o r m . T h i s r e p o r t d e s c r i b e s work done i n t h e Depar tmen t o f L i n g u i s t i c s a t t h e U n i v e r s i t y o f S t u t t g a r t . I t was s u p p o r t e d i n p a r t b y t h e German S c i e n c e F o u n d a t i o n p r o j . R o 2 4 5 / 1 2 . 694 U. Reyle and W. Frey