6.4, Elements of ABN Agents

Notes take from Argumentation-Based Negotiation (ABN) (2003), by Iyad Rahwan et al.

… how agents are specified, and how they reason about the interaction.

Conceptual elements of a classical negotiating agent (at an abstract level):
- Locution interpretation component, which parses incoming messages.
- Proposal database, wherein proposals may be stored for future reference.
- Proposal evaluation and generation component, which ultimately makes a decision about whether to accept, reject or generate a counterproposal, or even terminate the negotiation.
- Locution generation component, which sends the response to the relevant party or parties.
- Knowledge base of its mental attitudes (such as beliefs, desires, preferences and so on), as well as models of the environment and the negotiation counterpart(s).
In contrast, more sophisticated meta-level information can be explicitly exchanged between the ABN agents (giving rise to the necessity of additional components)…

1, Argument and Proposal Evaluation
We find it useful to distinguish between two types of considerations in argument evaluation:
- Objective – for example, by investigating the correctness of its inference steps, or by examining the validity of its underlying assumptions…
- Subjective – an agent may choose to consider its own preferences and motivations in making that judgement, or those of the intended audience…

Theoretical reasoning: Two agents reasoning about what is true in the world. Here it makes sense to adopt an objective convention that is not influenced by their individual biases and motivations…

Practical reasoning: Two participants engaged in a dialogue for deciding what course of action to take, or what division of scarce resources to agree upon, or what goals to adopt. Here it would make more sense for them to consider their subjective, internal motivations and perceptions, as well as the objective truth about their environment.

Even objective facts may be perceived differently by different participants, and such differences in perception may play a crucial role in whether or not participants are able to reach agreement…

In summary, agents participating in negotiation are not concerned with establishing the truth per se, but rather with the satisfaction of their needs…

One approach to proposal and argument evaluation is to assume agents are benevolent, using the following simple normative rule: “If I do not need a resource, I should give it away when asked.”

There are two types of conflict that would cause an agent to reject a request:
- It has a conflicting intention. In argumentation terms, it refuses the proposal if it can build an argument that rebuts it.
- It rejects one of the elements of the argument supporting the intention that denotes the request. In argumentation terms, it refuses the proposal because it can build an argument that undercuts it.

In order for argumentation to work, agents must be able to compare arguments. That is needed, for example, in order to be able to reject “weak” arguments…

An alternative trend in proposal and argument evaluation is to explicitly take into account the utility of the agent. The basic idea is that the agent would calculate and compare the expected utility in the cases where it accepts and rejects a particular proposal… This can be taken further by factoring the trust the agent has in its counterpart when calculating the expected values… Another approach is to introduce authority…

… The nature of argument evaluation depends largely on the object of negotiation and the way agents represent and update their internal mental states…

Challenges:
- Combining the objective (belief-based) and subjective (value-based) approaches to argument evaluation. For example, how can we combine the objective evaluation of the logical form of an argument with a subjective evaluation of its consequences based on utility, trust, authority, etc.?
- Providing unified argumentation frameworks that facilitate negotiation dialogues involving notions of goals, beliefs, plans, etc…
- … Understanding the space of possible influences ABN agents may (or must be able to) exert in the course of dialogue.

2, Argument and Proposal Generation
… This problem is concerned with generating candidate arguments to present to a dialogue counterpart…

In existing ABN frameworks, proposal generation is usually made as a result of some utility evaluation or planning process… Proposals may be accompanied by arguments, possibly generated using explicit (if-then) rules… or by providing “preconditions” for each argument to become a candidate argument… or, in a planning approach, generated in the process of proposal generation itself (stating the truth about its needs, plans, underlying assumptions, and so on, which ultimately caused the need to arise)…

Rahwan et al. [2] provide a characterisation of the types of arguments an agent can make in relation to the goal and belief structures of its counterpart…

Challenges:
- Providing a unified way of generating arguments by considering both objective and subjective criteria.
- A complete characterisation of the space of possible arguments (which in some frameworks could be infinite)…
- Understanding the influence of different factors, such as the interaction protocol, authority, expected utility, honesty etc. on argument generation. Specifically, how can authority be used in constructing an argument? Should an agent believe in an argument in order to present it? Can agents bluff? Etc.

3, Argument Selection
Given a number of candidate arguments an agent may utter to its counterpart, which one is the “best” argument from the point of view of the speaker?... Note that an agent need not generate all possible arguments before it makes a selection of the most suitable one…

The problem of argument selection can be considered the essence of strategy in ABN dialogues in general… However, there is very little existing work on strategies in multi-agent dialogues… Strategies depend on various factors such as the agents’ goals, the interaction protocol, the agents’ capabilities, the resources available to participants, and so on… Suitable argument selection in a negotiation context must take into account information about the negotiation counterpart…