tion, the time frame of the negotiation,
and the issues on which the negotiation
is being conducted. The number of parties participating in the negotiation process can be two (bilateral negotiations)
or more (multilateral negotiations).
For example, in a market there can be
one seller but many buyers, all involved
in negotiating over a certain item. On
the other hand, if the item is common,
there may also be many sellers taking
part in the negotiation process.
The negotiation environment also
consists of a set of objectives and issues
to be resolved. Various types of issues
can be involved, including discrete
enumerated value sets, integer-value
sets, and real-value sets. A negotiation
consists of multi-attribute issues if the
parties have to negotiate an agreement
that involves several attributes for each
issue. Negotiations that involve multi-attribute issues allow making complex
decisions while taking into account
18 The negotiation environment can consist of non-coopera-tive negotiators or cooperative negotiators. Generally speaking, cooperative
agents try to maximize their combined
joint utilities (see Zhang40) while noncooperative agents try to maximize
their own utilities regardless of the
other sides’ utilities.
Finally, the negotiation protocol de-
figure 1. Variations of the negotiation settings.
e: Guessing Heuristic
fines the formal interaction between
the negotiators—whether the negotiation is done only once (one-shot) or repeatedly—and how the exchange of offers between the agents is conducted.
A common exchange of offers model
is the alternating offers model.
addition, the protocol states whether
agreements are enforceable or not, and
whether the negotiation has a finite or
infinite horizon. The negotiation is said
to have a finite horizon if the length of
every possible history of the negotiation is finite. In this respect, time costs
may also be assigned and they may increase or decrease the utility of the negotiator.
Figure 1 depicts the different variations in the settings, along with the location of each system that is described
in the section “Tackling the Challenges.” For example, point D in the cube
represents bilateral negotiations with
multi-attribute issues and repeated
interactions, while point B represents
multilateral negotiations with a single
attribute for negotiation and a one-shot encounter.
The negotiation domain encompasses the negotiation objectives and
issues and assigns different values to
each. Thus, an agent may be tailored
to a given domain (for example, the
Diplomat agent22 described later is
tailored to a specific domain of the
Diplomacy game) or domain independent (for example, the QOAgent24 also
figure 2. example of virtual humans’ negotiations.
The information model
The information model dictates what
is known to each agent. It can be a
model of complete information, in
which each agent has complete knowledge of both the state of the world and
the preferences of other agents; or it
can be a model of incomplete information, in which agents may have only
partial knowledge of either the states
of the world or the preferences of other
agents (for example, bargaining games
with asymmetric information), or they
may be ignorant of the preferences of
the opponents and the states of the
33 The incomplete information
can be modeled in different ways with
respect to the uncertainty regarding
the preferences of the other party. One
approach to modeling the information
is to assume that there is a set of differ-