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 216

3.1 Walk-through example
We consider e-procurement scenarios where buyers seek to purchase earth observation
services from sellers (Stournaras, 2007). Each agent represents a user, i.e. a service requester
or a service provider. The negotiation of the fittest image is a complex task due to the
number of possible choices, their characteristics and the preferences of the users. Therefore,
this usecase is interesting enough for the evaluation of our argumentation-based mechanism
for decision-making (Bromuri et al., 2009; Morge & Mancarella, 2010). For simplicity, we
abstract away from the real world data of these features and we present here an intuitive
and illustrative scenario.
In our scenario, we consider a buyer that seeks to purchase a service s (

from a seller .
The latter is responsible for the four following concrete instances of services: s ( a )

x

)

, s ( b ) ,

s ( c )

. These four concrete services reflect the combinations of their features (cf
Tab. 1). For instance, the price of s ( a )

and s ( d )

is high ( Price ( a , high ) ), its resolution is low

( Resolution ( a , low ) ). According

to the preferences and the constraints of the user represented by the buyer : the cost must be
low ( cheap ); the resolution of the service must be high ( good ); and the delivery time must be
low ( fast ). Additionally, the buyer is not empowered to concede about the delivery time but
it can concede indifferently about the resolution and/or the cost. According to the preferences
and constraints of the user represented by the seller : the cost of the service must be high;
the resolution of the service must be low; and the delivery time must be high ( slow ). The
seller is not empowered to concede about the cost but it can concede indifferently about
the resolution or/and the delivery time. The agents attempt to come to an agreement on
the contract for the provision of a service s (

) and its delivery time is high ( DeliveryTime ( a , high )

) . Taking into account some goals, preferences

and constraints, the buyer (resp. the seller ) needs to interactively solve a decision-making
problem where the decision amounts to a service it can buy (resp. provide).

x

Service Price Resolution DeliveryTime
s ( a )

high low high

s ( b ) high high high

s ( c ) high low low

s ( d ) low low low

Table 1. The four concrete services and their features

The decision problem of the buyer can be captured by an abstract argumentation framework
which contains the following arguments:
• d 1 - He will buy s ( d ) if the seller accepts it since the cost is low;

• d 2 - He will buy s ( d ) if the seller accepts it since the delivery time is low;

• c - He will buy s ( c ) if the seller accepts it since the delivery time is low;

Due to the mutual exclusion between the alternatives, c attacks d 1 , c attacks d 2 , d 1 attacks c
and d 2 attacks c . We will illustrate our concrete argumentation framework for decisionmaking
with the decision problem of the buyer.

3.2 Decision framework
Since we want to provide a computational model of argumentation for decision making
and we want to instantiate it for particular problems, we need to specify a particular
language, allowing us to express statements about the various different entities involved