Rational agents and the processes and states of negotiation

This thesis shows how a verified and unambiguous theory of a protocol with known properties enables rational agents to interact in a negotiation process and to finally satisfy their goals using strategies and plans. This is achieved through an application of an extended form of propositional dynamic logic in the verification, validation and reasoning about interaction protocols in a multi-agent system. Agent interaction, as a key aspect in multi-agent systems and automated negotiation, has lead to a number of proposed agent communication languages and protocols. In contrast to a language, a rational agent can reason about a protocol to strategically plan possible courses of action in a bid to achieve its goals. Existing techniques for specifying protocols have resulted in faulty and ambiguous interaction protocols, leading to contradictory beliefs between agents. There remains a need for formally specifying and validating sharable interaction protocols with desirable properties. This thesis specifies, verifies and analyses protocols for automated negotiation through the application of Artificial Intelligence techniques. To this end, a meta-language called ANML is specified as an extension of propositional dynamic logic. The syntax and the semantics of ANML, including axioms and inference rules that hold in this normal modal system, are defined. Interaction protocols between agents can be concisely and completely specified in ANML allowing representation and reasoning about the states and processes of a negotiation. Examples of protocols for various types of negotiation are given as logical theories in ANML. This thesis verifies interaction protocols proposed in statecharts and AUML, [Odell and al. 2000], and show the inadequacy of these notations for specifying communication in multi-agent systems. For each verified protocol, its correct version is given in ANML. In addition to correctness, a protocol may exhibit safety, liveness or game theoretic properties. Axioms in ANML for a range of safety and liveness