Initial Thoughts and Plans

Thoughts following on from 18 December’s supervisor meeting.

The plan for the near future is to present an argumentative approach to sharing knowledge between collaborative agents. The envisioned approach will be based on sequences of dialogues. Each sequence of dialogues, between two or more agents, seeks to construct or attack a belief/standpoint. An agent may hold a belief until such time that it is put into question (i.e. challenged or attacked) and unsuccessfully defended. A challenge may be to simply express doubt with the intention of understanding the other agent’s standpoint, or to attack the other agent’s beliefs in promotion of an alternative standpoint. In the former case, an unsuccessful defence will result in retraction of the current standpoint. In the latter case, an unsuccessful defence will result in adoption of the promoted standpoint.

A dialogue takes place between two agents and its form will vary depending on whether a belief is being constructed or attacked. In the former case, a dialogue will consist of an enquiry followed by a response. In the latter case, a dialogue will consist of a challenge followed by a justification or acknowledgement of defeat.

The knowledge-base (beliefs) of agents will consist of facts, rules and assumptions; all shareable and defeasible. Intra- and inter-agent knowledge may be conflicting, and the process of sharing knowledge through argumentative discourse aims to resolve these conflicts. Though the joint knowledge of agents may be conflicting a joint argument (built on one line of reasoning) may not be.

As an example of a dialogue used to construct a belief, consider two agents (a1, a2) as follows:
a1 believes 'p holds if q and r hold' and 'q holds'.
a2 assumes 'r holds'.
An enquiry from a1 to a2 in the form “Does p hold given my belief ‘p holds if q and r hold’?” will result in a response from a2 in the form “I do not know if p holds, but I am currently assuming r holds”.
As a result of this dialogue, a1 can choose to adopt a positive standpoint for p given its belief of q and a2’s assumption on r.

As an example of a dialogue used to attack a belief, consider two agents (a1, a3) as follows:
a1 believes 'p holds if q and r hold' and 'q holds', and assumes 'r holds' allowing it to hold a positive standpoint for p.
a3 believes 'r does not hold'.
A challenge from a3 in the form “What is your basis for believing p given that r does not hold?” will result in either a1 finding and presenting another basis for p or acknowledging that it has no sound basis for its standpoint on p.

As an example of a sequence of dialogues used to construct a belief, consider three agents (a1, a4, a5) as follows:
a1 believes 'p holds if q and r hold' and 'q holds'.
a4 believes 'p holds if q and not s hold'.
a5 believes 's does not hold'.
An enquiry from a1 to a4 in the form “Does p hold given my belief ‘p holds if q and r hold’?” will result in a response from a4 in the form “I do not know if p holds, but I do know that ‘p holds if q and not s hold'." This will spark a further enquiry from a1 to a5 in the form “Does p hold given my beliefs ‘p holds if q and r hold’ and ‘p holds if q and not s hold’?” This enquiry will result in a response from a5 in the form “I do not know if p holds, but I do know that s does not hold”. This sequence of dialogues allows a1 to construct a positive standpoint for p on the basis of its belief that 'q holds', a4’s belief that 'p holds if q and not s hold' and a5’s belief that 's does not hold'.

The work will initially assume cooperativeness between agents ignoring elements such as deceitfulness, trust and reliability. Such elements will be considered later to bring in notions of competitiveness. Other open areas include:
- The notions of attack and defence (undercutting, rebuttal etc), and issues surrounding the semantics of beliefs (admissibility etc).
- What is an assumption, a factual truth and a rule? On what basis are they formed and defeated?
- The structure of arguments.
- The communication language and communication protocols: How does an agent know who to contact for particular knowledge? Should dialogues be restricted to one-to-one?
- Agent varieties - tying in with issues of cooperativeness and competitiveness: Are all agents the same with respect to how they enquire, respond, challenge and justify?