Specifying norm-governed computational societies

Abstract

Electronic markets, dispute resolution and negotiation protocols are three types of application domains that can be viewed as open agent societies. Key characteristics of such societies are agent heterogeneity, conflicting individual goals and unpredictable behavior. Members of such societies may fail to, or even choose not to, conform to the norms governing their interactions. It has been argued that systems of this type should have a formal, declarative, verifiable, and meaningful semantics. We present a theoretical and computational framework being developed for the executable specification of open agent societies. We adopt an external perspective and view societies as instances of normative systems. In this article, we demonstrate how the framework can be applied to specifying and executing a contract-net protocol. The specification is formalized in two action languages, the C + language and the Event Calculus, and executed using respective software implementations, the Causal Calculator and the Society Visualizer. We evaluate our executable specification in the light of the presented case study, discussing the strengths and weaknesses of the employed action languages for the specification of open agent societies.

Executable specification of open multi-agent systems

“…(As mentioned earlier in the paper, in [2] we presented a comparison of C + and EC with respect to open MAS specification.) Like EC, C + was employed to express all operations on commitments as well as the effects of the agents' actions.…”

“…The Event Calculus (EC) [40], a formal, intuitive and well-studied action language (see [2] for an EC specification of a contract-net protocol).…”

“…(See [2] for a comparison of their relative strengths.) In this paper we will use EC because an EC implementation (in terms of logic programming) has proved to be more efficient than a C + or nC + implementation (employing the Causal Calculator, a software tool supporting computational tasks regarding the C + language) for the provision of 'run-time services'.…”

“…Such a specification would be similar to that of NetBill presented in the previous sections or to other protocol specifications presented elsewhere [2,1]. We omit the details here to save space.…”

“…In previous publications we were concerned with other aspects of normative systems; in [2] we presented a comparison of action formalisms for open MAS specification while in [1] we presented a specification of a dispute resolution protocol. In these previous papers we discussed the process of role-management but did not formalise it.…”