ALVEN: A Study on Motion Understanding by Computer

1.0 INTRODUCTION The main goa l o f t h i s r e s e a r c h , f rom an AI v i e w p o i n t is the development o f a framework f o r Mo t ion Unders tand ing by Computer. Th is f rame­ work i s expected t o p r o v i d e : (a) A r e p r e s e n t a t i o n of knowledge f o r mot ion concep ts , based on frames [Minsky75] and semant ic networks [Brachman79] . (b) The d e s c r i p t i o n of bas i c mot ion concepts such as v e r b s , shape t r a n s f o r m a t i o n s and tempora l i n f o r m a t i o n i n terms o f the knowledge r e p r e s e n t a ­ t i o n proposed, based on past work i n mot ion r e ­ p r e s e n t a t i o n [ B a d l e r 7 5 ] , [ T s o t s o s 7 6 ] ; (c ) The development o f a l g o r i t h m s f o r the a n a l y ­ s i s o f p i c t o r i a l da ta in terms o f a mot ion knowledge base. These a l g o r i t h m s w i l l be e x p e c t ­ ed to genera te a d e s c r i p t i o n of the o b j e c t s and mot ions found i n the p i c t o r i a l da ta a t d i f f e r e n t l e v e l s o f a b s t r a c t i o n , f rom d e t a i l e d LV w a l l k i n e m a t i c s to summary s ta tements us ing E n g l i s h ­ l i k e v e r b s . The r e c o g n i t i o n c o n t r o l s t r u c t u r e is based on the concept o f c o m p e t i t i o n and c o ­ o p e r a t i o n among l o c a l hypotheses [Zucker78] both a t t he low (image) l e v e l [Rose fe l d ,Zucke r , Humel76l and a t h i g h e r ( concep tua l ) l e v e l s . ALVEN (A L e f t V e n t r i c u l a r Wa l l Mo t ion A n a l y ­ s i s Computer C o n s u l t a n t ) , i s a system f o r the a n a l y s i s o f c inecard ioang iog rams ( f i l m s o f the human l e f t v e n t r i c l e ) . Given such a f i l m , the sys tem's j o b i s to generate a concep tua l des ­ c r i p t i o n o f the shapes and mot ions e x h i b i t e d in the f i l m b y the l e f t v e n t r i c u l a r w a l l , n o t i n g a b n o r m a l i t i e s and unusua l occu r rences . From a med i ca l p o i n t of v i e w , ALVEN*s impor ­ tance i s based on i t s a b i l i t y t o p r o v i d e an assessment o f the human l e f t v e n t r i c l e ( h e r e i n ­ a f t e r LV ) , as a f u n c t i o n i n g musc le . The aim of the research i s t w o f o l d : (a) To produce a system t h a t can a i d in the a n a l y s i s o f c i neca rd ioang iog rams , and wh ich p r o ­ duces c o n s i s t e n t and o b j e c t i v e d e s c r i p t i o n s o f l e f t v e n t r i c u l a r w a l l dynamics, (b) To p r o v i d e a framework f o r the r e p r e s e n t a t i o n of med ica l knowledge about the dynamics of the human l e f t v e n t r i c l e . ALVEN is a f i r s t s tep towards a c h i e v i n g these o b j e c t i v e s . Past d e s c r i p t i o n s of ALVEN may be found in [Tso tsos78 ] and [ T s o t s o s 7 9 ] . 2 .0 REPRESENTATION OF KNOWLEDGE 2 .1 What Needs to be Represented? The main concern o f t h i s r e p r e s e n t a t i o n a l f o rma l i sm is how mot ion concepts are to be r e p r e ­ sented and o rgan ized i n t o a genera l mo t ion con ­ cept and p r o b l e m s p e c i f i c concept knowledge base. There are s e v e r a l types of mot ion concepts : a) speed of an o b j e c t b ) t r a j e c t o r y o f mot ion c ) d e s c r i p t i v e mot ion verbs d ) q u a l i t a t i v e t r a j e c t o r y d e s c r i p t i o n s d i r e c t i o n a l s e) changes of an o b j e c t ' s p r o p e r t i e s f ) tempora l concep ts : d u r a t i o n , s t a r t and end t i m e , r e l a t i v e t i m i n g o f e v e n t s . In a d d i t i o n , the r e p r e s e n t a t i o n must be f l e x i b l e enough t o handle " f u z z y " d a t a , d i f f e r e n t l e v e l s o f a b s t r a c t i o n i n c l u d i n g l i n g u i s t i c l e v e l s , and to rep resen t enough i n f o r m a t i o n f o r a p p r o x i ­ mate r e g e n e r a t i o n o f analyzed m o t i o n s . 2.2 R e p r e s e n t a t i o n a l B u i l d i n g B locks The bas ic e n t i t i e s o f the r e p r e s e n t a t i o n are c a l l e d frames and are used to model a b s t r a c t concepts such as t h a t of HEART or BEATing. The i n s t a n t i a t i o n s o f the a b s t r a c t concepts o f the r e a l w o r l d a re model led i n the r e p r e s e n t a t i o n by frame tokens (o r s imp l y t o k e n s ) . The INSTANCE-OF r e l a t i o n s h i p r e l a t e s tokens to the frames o f wh ich they are i n s t a n c e s . Thus, " J o h n ' s LV" , an i ns tance which rep resen t s a p a r t i c u l a r l e f t v e n ­ t r i c l e , i s r e l a t e d t o "LV" th rough the INSTANCEOF r e l a t i o n s h i p . * Th is paper is a summary of [Tso tsos79 ] .