Object models for computer aided design

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t􁪽􋵥e srrall e􁪽􋵪ject spaCE than 􁪽􋴚􁪽􋵩 is in the 􁪽􋵊Jch larger 􁪽􋴻;: a c e i r. ....,:-.:. cr. e r'. t i : i. e 5 ex i 5: i r: Vi: .z..􁪽􋴺: • 172 f i l e :: :-: e a C 'y' a n t a 9 e s 0 f t his " 1 0 C 2 1 i z a t i 0 r. " are also ce􁪽􋵣c􁪽􋵳strited by the problere of generating a new Ficture in :􁪽􋴚􁪽􋴚􁪽􋴚􁪽􋴚􁪽􋵓Se tc SC􁪽􋶬€ user interac􁪽􋵩io􁪽􋴮. v;ith ctject rr.o􁪽􋵥els it :5 senerally possible to transfer all the objects needed fer a ;:artic􁪽􋵬lar design task into the prosralT WCrkS?2ce. T􁪽􋵥e 9raphic processer can process these structures entirely in 􁪽􋵡ain me􁪽􋵯ory. It is thus relatively easy to 􁪽􋵰pcate the picture in real t i me (i.e. so the operator cannot perceive a celay). T􁪽􋵩i5 sort of real tiDe response woulj 􁪽􋵥e much 􁪽􋵣cre difficult 􁪽􋵩ithcut otject structures. \'I􁪽􋵩ith other systeros :'t 􁪽􋵳s􁪽􋵡al1y cannot be guaranteed that all of the i r: me i n r e r o r v , S8 c r.e c r rr c r e c i s « e c c e s s e s rt a v be re c e s s a r v t c S􁪽􋵣ch disk accesses 􁪽􋵡ake real ti􁪽􋵥e response extrerrely difficult to ac:-::'eve. 􁪽􋵥e ta􁪽􋵥e also clai􁪽􋵥ed t􁪽􋵡at ebjects provide 􁪽􋴚􁪽􋵃Ch3r.is􁪽􋵦 for partitioning the IToce1 1;-;to e:-::1:ies. fecause otjects m􁪽􋵹y have a 􁪽􋵯ore co􁪽􋵰plex iriter;"lal s􁪽􋵲rGct􁪽􋵲r􁪽􋴬, 3 sin􁪽􋵬le otjec: can represent i treader class cf : :-. i :-: 􁪽􋵅 E : :. a r. can "record", or "iterr" in other !􁪽􋵲 rro􁪽􋵴t ot􁪽􋵥er 5cherres an􁪽􋴿 ?rc;erties 􁪽􋵨hat ccccr a