Some Thoughts about Representing Knowledge in Instructional Systems

T h i s paper examines the p o s s i b i l i t i e s o f a p p l y i n g A I -Me thodo logy deve loped f o r n a t u r a l language q u e s t i o n a n s w e r i n g systems t o c o m p u t e r a i d e d i n s t r u c t i o n a l sys tems. P a r t i c u l a r l y , i t f ocusses on how semant ic n e t s can be ex tended to hand le p r o c e d u r a l know ledge , and how an i n s t r u c t i o n a l model can be expressed in te rms o f g o a l d i r e c t e d p rocesses sepa ra ted f rom s u b j e c t m a t t e r knowledge. I n t r o d u c t i o n F u n c t i o n a l l y , q u e s t i o n a n s w e r i n g systems and c o m p u t e r a i d e d i n s t r u c t i o n a l systems (CAI -sys tems) are s i m i l a r , and i t seems a p p r o p r i a t e t o t r a n s f e r A l t e c h n i q u e s d e ve loped f o r Q/A-systems (11 ,13) t o C A I sys tems. But so f a r , r esea rch on Q/Asystems has n o t g i v e n much t h o u g h t to t he q u e s t i o n s a user c o u l d or shou ld be a s k e d , o r how t h e sys tem ' s r e p l y shou ld be e x pressed as to be e a s i l y u n d e r s t a n d a b l e by t h e u s e r . These f e a t u r e s a re no t o n l y r e q u i r e d i n t u t o r a l d i a l o g u e , b u t shou ld a l s o be p r e s e n t i n any i n t e r a c t i v e sys tem, where a t l e a s t two p a r t n e r s j o i n t l y s t r i v e to ach ieve a g o a l , and each may reques t use o f t h e c a p a b i l i t i e s o f t h e o t h e r . C l e a r l y , a t e a c h e r needs some knowledge o f h i s s t u d e n t ' s knowledge and g o a l s a s i d e f rom knowledge about s u b j e c t m a t t e r . That knowledge is r e f e r r e d to as a usermodel. Other i n t e r a c t i v e a p p l i c a t i o n s l i k e o p e r a t i n g sys tems , debuggers f o r p r o gramming l anguages , o r i n f o r m a t i o n r e t r i e v a l systems would a l s o b e n e f i t f rom e x p l i c i t l y c o n s i d e r i n g a model o f t h e user i n p r e p a r i n g t h e i r messages. We w i l l o u t l i n e (1) how s u b j e c t m a t t e r knowledge may be r e p r e s e n t e d in semant i c n e t s , and t h e n (2) how p l a n n i n g o f i n s t r u c t i o n i s d i r e c t e d b y a n i n s t r u c t i o n a l m o d e l . B u i l d i n g semant ic n e t s i n a s u b j e c t a rea SCHOLAR by C a r b o n e l l (3) and SOPHIE by Brown (2) a r e examples of the use of a semant ic ne t f o r r e p r e s e n t i n g s u b j e c t m a t t e r knowledge and u s i n g i t i n gene r a t i n g p r o b l e m s , o r answer ing q u e r i e s . Simmons has h y p o t h e s i z e d t h a t semant ic n e t s may se rve as the c e n t r a l c o g n i t i v e s t r u c t u r e ( 1 1 ) . We w i l l show how a semant i c ne t o f a s u b j e c t m a t t e r a rea can be b u i l t ( us i ng the n o t a t i o n o f ( 8 ) ) , and how the n o t i o n of a semant ic ne t may be expanded i n o r d e r t o ach ieve q r e a t e r f l e x i b i l i t y i n u s i n g i t . Bas ic o b j e c t s and r e l a t i o n s F i r s t , c e r t a i n concep ts a re d e c i d e d t o b e p r e r e q u i s i t e and known to any s t u d e n t . Some o b j e c t s and r e l a t i o n s a re a l s o used a s p r i m i t i v e s i n t he p r o b l e m s o l v i n g component o f the sys tem. The r e l a t i o n " n o r t h o f " may e i t h e r be assumed b a s i c or e x p l a i n e d t o t h e s t u d e n t i n te rms o f l a t i t u d e , a s w e l l a s computed i n te rms o f l a t i t u d e . I n choos ing b a s i c r e l a t i o n s and o b j e c t s , i t has t o b e c o n s i d e r e d t h a t natu r a l language sen tences may be conve n i e n t l y g e n e r a t e d .