Intelligent systems, e.g. decision support systems often contain inconsistent and conflicting information. The methods of the classical logics could not be applied for such knowledge bases (KB), as there no mechanisms for detection and solving conflicts. In addition classical methods of inference do not have mechanisms of ‘revision’ of previously made conclusions. It is proposed to use the mechanism of argumentation for dealing with conflicts and inconsistency.
Argumentation is a good way to deal with inconsistent knowledge bases. Argumentation is usually considered as the process of constructing the assumptions of solving the analyzed problem. Typically, this process involves the construction of hypothesis, the detection of conflicts and the search of admissible solutions. In contrast to the classical logic, in the theory of argumentation there may be arguments "for" and "against" certain assumptions. It is necessary to show that there are more arguments "for" than “against” some assumption to confirm it. Thus, one argument is not enough to say assumption is plausible, but the superiority of arguments over counterarguments already does this.
There are several formalizations of the arY. Shoham , the G.A.W. Vreeswijk’ssystem and systems based on defeasible reasoning (J. L . Pollock)  and some others. We’ll consider the development of defeasible argumentation systems that use the first order logic as an underlying language and based on the theory of defeasible reasoning proposed by John Pollock .