Arguing over Goals for Negotiation: Adopting an Assumption-Based Argumentation Decision Support System - Efficient Decision Support Systems: Practice and Challenges from Current to Future - page 212

representing knowledge, goals, and decisions. Preferences are attached to goals. These
concrete data structures consist of information providing the backbone of arguments. Due to
the abductive nature of practical commonsense reasoning, arguments are built by reasoning
backwards. Moreover, arguments are defined as tree-like structures. Our framework is
equipped with a computational counterpart (in the form of a formal mapping from it into
a set of assumption-based argumentation frameworks). Indeed, we provide the mechanism
for solving a decision problem, modeling the intuition that high-ranked goals are preferred
to low-ranked goals which can be withdrawn. Thus, we give a clear semantics to the
decisions. In this way, our framework suggests some decisions and provides an interactive
and intelligible explanation of this choice. Our implementation, called MARGO, is a
tool for multi-attribute qualitative decision-making as required, for instance in agent-based
negotiation or in service-oriented agents. In a more practical context, our framework is
amenable to industrial applications. In particular, MARGO has been used within the the
ArguGRID project 1 for service selection and sevice negotiation.
The paper is organised as follows. Section 2 introduces the basic notions of argumentation
in the background of our work. Section 3 defines the core of our proposal, i.e. our
argumentation-based framework for decisionmaking. Firstly, we define the framework which
captures decision problems. Secondly, we define the arguments. Thirdly, we formalize
the interactions amongst arguments in order to define our AF (Argumentation Framework).
Finally, we provide the computational counterpart of our framework. Section 4 outlines
the implementation of our AF and its usage for service-oriented agents. Finally, section 5
discusses some related works and section 6 concludes with some directions for future work.

2. Background
Our argumentation approach is based on Dung's abstract approach to defeasible
argumentation (Dung, 1995). Argumentation is abstractly defined as the interaction amongst
arguments, reasons supporting claims, which can be disputed by other arguments. In his
seminal work, Dung considers arguments as atomic and abstract entities interacting through
a binary relation over these interpreted as “the argument x attacks the argument y ”. More
formally, an abstract argumentation framework (AAF for short) is defined as follows.
Definition 1 (AAF) . An abstract argumentation framework is a pair aaf = A , attacks

where .When

( a , b ) ∈ attacks , we say that a attacks b . Similarly, we say that the set S of arguments attacks b
when a ∈ S .
This framework is abstract since it specifies neither the nature of arguments nor the semantics
of the attack relation. However, an argument can be viewed as a reason supporting a claim
which can be challenged by other reasons.
According to this framework, Dung introduces various extension-based semantics in order to
analyse when a set of arguments can be considered as collectively justified.

A

is a finite set of arguments and attacks ⊆A×A is a binary relation over

A

Definition 2 (Semantics) . Let aaf = A , attacks be an abstract argumentation framework.

For S ⊆A a set of arguments, we say that:

• S is conflict-free iff

∀ a , b ∈ S it is not the case that a attacks b ;

1 http://www.argugrid.eu