“Itistypicaltoadoptthedefined(theoretical)modelingapproachwhentheunderlyingmechanismsbywhichaprocessoperatesarereasonablywellunderstood.Whentheprocessistoocomplicatedforthedefinedapproach,theempiricalapproachistheappropriatechoice.”ProcessDynamics,Modeling,andControl,OgunnaikeandRay,Ox