Object models for computer aided design

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10 􁪽􋴺:􁪽􋴵5S. Khe􁪽􋵴 the o?er􁪽􋵴tcr can rotate and tra􁪽􋵳slate t􁪽􋵥e a goo􁪽􋵩 i􁪽􋵴t􁪽􋴚􁪽􋵴t􁪽􋵶ve idea of 􁪽􋵴ts three 6i􁪽􋵥e􁪽􋵳s􁪽􋵯on21 stape. 􁪽􋵮nt􁪽􋴚􁪽􋵴ticn is qu􁪽􋵣ckly lost 􁪽􋵩ith Etat􁪽􋵣c pictures. In or::er the 􁪽􋵩icture 􁪽􋵵ust te u?=ated 15 to 20 t􁪽􋵭mes a secon􁪽􋴮. 􁪽􋵯owever, one wants wants to be a􁪽􋵬le tc 􁪽􋵮nteract w􁪽􋵴th the otject represented by the 􁪽􋴚􁪽􋵣cture, ane not j􁪽􋵳st w􁪽􋵴th the picture. S􁪽􋵮nce non-spa-::al inforrrat􁪽􋵯on 􁪽􋵡ay serve to constrain cr be 􁪽􋵯od:f􁪽􋵥ej 􁪽􋵹y :he 􁪽􋵮nteracticn, t h i s h i c h speec access reqc􁪽􋵲rerrent incl􁪽􋵤des both spatial and non-spatial data. On the other hand, if one considers the protlem of in :'solation, the result􁪽􋵮ng sy5te􁪽􋵲 rray not be suitable for general moceling. There have been ITany "picture edit􁪽􋴚􁪽􋵧g" systerrs develo;ed 􁪽􋴚􁪽􋴺:􁪽􋴚􁪽􋵣 ca􁪽􋵅 E3sily 􁪽􋵲raw ane 􁪽􋵣cdify picture􁪽􋵯 of so􁪽􋵥e c􁪽􋵪ject, like a car, but can not be used to really cesign ane There is ffiuch roore to a car than a collection of surfaces. Besides its shape, a car coor has and properties, cost, s􁪽􋵢b-corrponents, and all sorts of other attributes. All of these 􁪽􋵲ro􁪽􋵥erties are inter-related. To se􁪽􋵡arate the s􁪽􋵡at􁪽􋵡al and non-spatial properti􁪽􋵳s 􁪽􋵮nto separate structures 􁪽􋵡akes it difficult, and somet􁪽􋵭mes impossible, to generate an aeequate 􁪽􋵯odel for design ane analysis applications.