| OCR Text |
Show 166 :: is 2 iport2t feature of the 5yste :at it ca be :;e:2ete relatively easily o s sITall ccpcter. Ke have said that cbjects provide a 0re efficiet desi te tc be hi?hly inter-relate. For e x err.p Le , all e:hanism for ic;lerre:ing data bases fer corrputer aided esign a;lications t2n has been achieved without this ccncet. The data structres needed i corrputer aided cf te :eFresentatiens ef the pelyhedron (see chapter 3) h2e cre lik fields tan data fields. The 0: these inter-entity links thus becomes an important efficiency i£sue. I object rr.oo e Ls t as r e are two levels of "entities" (0e:ts ad a:trites) with a differet linkage et2i2 ost f e inter-entity links are 2::rcte lave! (e.g. fsces, ecges, ?olyedro). 3ecause otjects are closec, these liks can be iGleroented very efficiently. In the iffip1eroentation cecuentd in A?pencix I, esch attricte has one 16 c; fie: fer linking into he a:triute list to whic each attribute rrst belong and a single 16 bit field fer each attritte list header or attribute pointer field in the c;:' , l:!ce attr:'bt..;tes are bet..:ncec ar.a the whole cject resides ir. 2 rrerrory 2t ece, these links can be fcrterore, he:e iE o r.eed for |
