3 research outputs found
Graduality in Argumentation
Argumentation is based on the exchange and valuation of interacting
arguments, followed by the selection of the most acceptable of them (for
example, in order to take a decision, to make a choice). Starting from the
framework proposed by Dung in 1995, our purpose is to introduce 'graduality' in
the selection of the best arguments, i.e., to be able to partition the set of
the arguments in more than the two usual subsets of 'selected' and
'non-selected' arguments in order to represent different levels of selection.
Our basic idea is that an argument is all the more acceptable if it can be
preferred to its attackers. First, we discuss general principles underlying a
'gradual' valuation of arguments based on their interactions. Following these
principles, we define several valuation models for an abstract argumentation
system. Then, we introduce 'graduality' in the concept of acceptability of
arguments. We propose new acceptability classes and a refinement of existing
classes taking advantage of an available 'gradual' valuation
"Minimal defence": a refinement of the preferred semantics for argumentation frameworks
Dung's abstract framework for argumentation enables a study of the
interactions between arguments based solely on an ``attack'' binary relation on
the set of arguments. Various ways to solve conflicts between contradictory
pieces of information have been proposed in the context of argumentation,
nonmonotonic reasoning or logic programming, and can be captured by appropriate
semantics within Dung's framework. A common feature of these semantics is that
one can always maximize in some sense the set of acceptable arguments. We
propose in this paper to extend Dung's framework in order to allow for the
representation of what we call ``restricted'' arguments: these arguments should
only be used if absolutely necessary, that is, in order to support other
arguments that would otherwise be defeated. We modify Dung's preferred
semantics accordingly: a set of arguments becomes acceptable only if it
contains a minimum of restricted arguments, for a maximum of unrestricted
arguments.Comment: 8 pages, 3 figure