 Gerald Vreeswijk (Vreeswijk 1997) has built upon Dung’s framework by introducing preference relations among arguments. The relation of relative conclusive force could be determined by such factors as the presence or absence of defeasible rules, the occurrence of a premise of one argument as the conclusion of another, the number of steps in the argument, or the use in the arguments of defeasible rules with varying degrees of reliability. The HERMES system of Karacapilidis and Papadias (Karacapilidis and Papadias 2001) implements numeric weights for reasons for and against a conclusion.