6.3, External Elements of ABN Frameworks

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

1, Communication Language & Domain Language
A negotiation framework requires a language that facilitates such communication. Elements of the communication language are usually referred to as locutions or utterances or speech acts.

Basic (traditional) locutions include propose, accept and reject. ABN locutions would allow agents to pass meta-information either separately or in conjunction with other locutions.

In addition, agents often need a domain language for referring to concepts of the environment, the different agents, proposals, and so on.

In multi-agent systems, two major proposals for agent communication have been advanced:
- the Knowledge Query and Manipulation Language (KQML) [1];
- the Foundation for Intelligent Physical Agents’ Agent Communication Language (FIPA ACL) [2], for which the contents of the messages can be in any domain language.

FIPA ACL has been given semantics in the form of pre- and post-conditions of each locution… While it offers the benefits of being a more or less standard agent communication language, it fails to capture all utterances needed in a negotiation interaction… While such locutions may be constructed by injecting particular domain language statements within locutions similar to those of FIPA ACL, the semantics of these statements fall outside the boundaries of the communication language…

In negotiation, the domain language must, at least, be capable of expressing the object of negotiation… There is also a meta-language for explicitly expressing preferences…

Challenges (in the design of domain and communication languages for ABN):
- There is a need to provide rich communication languages with clear semantics [3]… There are oppurtunities for extending the model of [3] with a richer argumentation system.
- The building of common, standardised domain languages that agent designers can use in order to plug their agents into heterogeneous environments [4, 5]… There is a need for exploring the suitability of these domain languages for supporting ABN and understanding how arguments can be expressed and exchanged.

2, Negotiation Protocol
… a negotiation framework should also specify a negotiation protocol (a formal set of conventions governing the interaction among participants) in order to constrain the use of the language. This includes the interaction protocol as well as other rules of the dialogue, as follows:
- Interaction protocol: specifies, at each stage of the negotiation process, who is allowed to say what… It might be based solely on the last utterance made, or might depend on a more complex history of messages between agents.
- Rules for admission.
- Rules for participant withdrawal.
- Termination rules.
- Rules for proposal validity.
- Rules for outcome determination.
- Commitment rules.

In ABN, the negotiation protocol is usually more complex (larger number of locutions and rules) than those in non-ABN. This leads to computational complexity arising from processes such as checking the locutions for conformance with the protocol given the history of locutions.

… Interaction protocols can be either specified in an explicit accessible format (finite state machines, dialogue games [3]), or be only implicit and hardwired into the agents’ specification (specified using logical constraints expressed in the form of if-then rules).

Challenges:
- As faced in the design of argumentation protocols in general, there is a need for qualities such as fairness, clarity of the underlying argumentation theory, discouragement of disruption by participants, rule consistency, and so on.
- Termination… It is not clear whether results strongly dependent on particular underlying logical systems can be generalised to a variety of protocols without regard to the internal agent architecture.
- Guaranteed success (i.e. terminating with agreement)…
- Conformance checking (i.e. whether a particular utterance is acceptable, given the history and context of interaction)…
- The design of admission rules in negotiation protocols… To our knowledge, no ABN framework includes external rules that govern admission to the negotiation dialogue… More work needs to be done on investigating the effect of different admission rules on the outcome of negotiation…

3, Information Stores
In some ABN frameworks, there is no explicit centralised information store available. Instead, agents internally keep track of past utterances. However, in many negotiation frameworks there is a need to keep externally accessible information during interaction…

Commitment store: A type of information store used as a way of tracking the claims made by participants in dialogue games… Note that commitment stores should not be confused with the interaction history…

The representation and manipulation of information stores is not a trivial task, and has significant effects on both the performance and outcomes of negotiation dialogues. In particular, information store manipulation rules have a direct effect on the types of utterances agents can make given their previous utterances, the properties of the dialogue, and the final outcome.

Some of the key questions that need to be addressed in an ABN framework are:
- Under what conditions should an agent be allowed to retract its commitments and how would this affect the properties of dialogues?
- Under what conditions should an agent be forced to retract its commitments to maintain consistency?
- Specific to negotiation dialogues, do commitments to providing, requesting and exchanging resources require different treatments in other types of dialogue, such as persuasion or information seeking?