▁of ▁int rees ▁and ▁out trees . ▁ ▁sp - graph ▁ ▁Given ▁preced ence ▁relation ▁in ▁form ▁of ▁a ▁series ▁parallel ▁graph . ▁ ▁bounded ▁height ▁ ▁Given ▁preced ence ▁relation ▁where ▁the ▁longest ▁directed ▁path ▁is ▁bounded ▁by ▁a ▁constant . ▁ ▁level ▁order ▁ ▁Given ▁preced ence ▁relation ▁where ▁each ▁vertex ▁of ▁a ▁given ▁level ▁l ▁( i . e . ▁the ▁length ▁of ▁the ▁longest ▁directed ▁path ▁starting ▁from ▁this ▁vertex ▁is ▁l ) ▁is ▁a ▁prede cess or ▁of ▁all ▁the ▁vertices ▁of ▁level ▁l - 1 . ▁ ▁interval ▁order ▁ ▁Given ▁preced ence ▁relation ▁for ▁which ▁one ▁can ▁associate ▁to ▁each ▁vertex ▁an ▁interval ▁in ▁the ▁real ▁line , ▁and ▁there ▁is ▁a ▁preced ence ▁between ▁x ▁and ▁y ▁if ▁and ▁only ▁if ▁the ▁half ▁open ▁intervals ▁x =[ s _ x , e _ x ) ▁and ▁y =[ s _ y , e _ y ) ▁are ▁such ▁that ▁e _ x ▁is ▁smaller ▁than ▁or ▁equal ▁to ▁s _ y . ▁ ▁quasi - interval ▁order ▁ ▁Qu asi - interval ▁orders ▁are ▁a ▁super class ▁of ▁interval ▁orders ▁defined ▁in ▁Mou k rim : ▁Opt imal ▁sched uling ▁on ▁parallel ▁machines ▁for ▁a ▁new ▁order ▁class , ▁Oper ations ▁Research ▁Let ters , ▁ 2 4 ( 1 ): 9 1 - 9 5 , ▁ 1 9 9 9 . ▁ ▁over - interval ▁order ▁ ▁Over - interval ▁orders ▁are ▁a ▁super class ▁of ▁quasi - interval ▁orders ▁defined ▁in