rel ational ▁mapping ▁is ▁an ▁output ▁of ▁the ▁O O ▁design ▁process . ▁However , ▁it ▁is ▁possible ▁to ▁develop ▁the ▁rel ational ▁data ▁model ▁and ▁the ▁object - orient ed ▁design ▁artifact s ▁in ▁parallel , ▁and ▁the ▁growth ▁of ▁an ▁artifact ▁can ▁stim ulate ▁the ▁ref in ement ▁of ▁other ▁artifact s . ▁ ▁Object - orient ed ▁concepts ▁ ▁The ▁five ▁basic ▁concepts ▁of ▁object - orient ed ▁design ▁are ▁the ▁implementation ▁level ▁features ▁that ▁are ▁built ▁into ▁the ▁programming ▁language . ▁ ▁These ▁features ▁are ▁often ▁referred ▁to ▁by ▁these ▁common ▁names : ▁ ▁Object / Class : ▁A ▁tight ▁coupling ▁or ▁association ▁of ▁data ▁structures ▁with ▁the ▁methods ▁or ▁functions ▁that ▁act ▁on ▁the ▁data . ▁This ▁is ▁called ▁a ▁class , ▁or ▁object ▁( an ▁object ▁is ▁created ▁based ▁on ▁a ▁class ). ▁ ▁Each ▁object ▁serves ▁a ▁separate ▁function . ▁ ▁It ▁is ▁defined ▁by ▁its ▁properties , ▁what ▁it ▁is ▁and ▁what ▁it ▁can ▁do . ▁ ▁An ▁object ▁can ▁be ▁part ▁of ▁a ▁class , ▁which ▁is ▁a ▁set ▁of ▁objects ▁that ▁are ▁similar . ▁Information ▁hiding : ▁The ▁ability ▁to ▁protect ▁some ▁components ▁of ▁the ▁object ▁from ▁external ▁entities . ▁This ▁is ▁realized ▁by ▁language ▁keywords ▁to ▁enable ▁a ▁variable ▁to ▁be ▁declared ▁as ▁private ▁or ▁protected ▁to ▁the ▁ow ning ▁class . ▁In herit ance : ▁The ▁ability ▁for ▁a ▁class ▁to ▁extend ▁or ▁override ▁functionality ▁of ▁another ▁class . ▁ ▁The ▁so - called ▁subclass ▁has ▁a ▁whole ▁section ▁that ▁is