Information Technology Reference
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There are several reasons for taking interests into account. First, underlying interests
can explain and eliminate conditional preferences. Consider the following example. If
it rains, I prefer to take my umbrella, but if it doesn't, I prefer not to take it. This
is a conditional preference; my preference over taking my umbrella depends on the
circumstance of rain. Underlying interests can explain such conditional preferences: I
prefer to take my umbrella when it rains because I do not want to get wet, and I prefer
not to take it when it's dry because I don't want to carry things unnecessarily. If we
take such interests as criteria on which to base preference, we can eliminate conditional
preferences entirely. We will get back to this in more detail later. Second, interest-based
negotiation is said to lead to better outcomes than position-based negotiation [3,4]. By
understanding one's own and the other party's reasons behind a position and discussing
these interests, people are more likely to find more creative options in a negotiation and
by that reach a mutually acceptable agreement more easily. A well-known example is
that of the two sisters negotiating about the division of an orange. They both want the
orange, and end up splitting it in half. Had they known each other's underlying interests,
they would have reached a better deal: one sister only needed the peel to make a cake
and would gladly have let the other sister have all of the flesh for her juice. Third,
thinking about underlying interests is a very natural, human thing to do. Interests are
what really matters to people, they are what drive them in their decisions and opinions.
Taking underlying interests explicitly into account will result in a better model of human
preferences. Such a model is also suited for explanation of the reasoning and advice of
a support system.
This last point brings us to the motivation for using argumentation to reason about
interest-based preferences. Reasoning by means of arguments is a very human type of
reasoning. People often base their decisions on (mental) lists of arguments in favour
of and against certain decisions. Therefore argumentation is suitable for explanation of
a system's reasoning to a human user. Another advantage of argumentation is that it
is a kind of defeasible reasoning. It is able to reason with incomplete, uncertain and
contradictory information. Finally, argumentation can be used to (try to) persuade the
opponent during negotiation (but this is outside the scope of this paper).
The paper is organised as follows. In Section 2 we introduce and discuss the most
important concepts that we will use throughout the paper. Then, in Section 3, we give
an overview of existing approaches to preferences and underlying interests. We give
some more details about qualitative multi-criteria preferences in Section 4. In Section
5 we motivate the explicit modelling of underlying interests, illustrated with examples.
Our own approach is presented in Section 6. Finally, Section 7 concludes the paper.
2
Concepts
Before we go on, we will clarify some important concepts that we will use. In ne-
gotiation,
issues
are the matters which are under negotiation. An issue is a concrete,
negotiable aspect such as monthly salary or number of holidays. Every issue has a set
or range of possible values. The value of an issue in a given instance can be objectively
determined (e.g.
2400, 30 days). Issues and their possible values typically depend on
the domain. Besides the issues under negotiation, there may be other properties of a
e
