Modelling and visualising agent conversations

The notion of conversations, and their associated conversation protocols, as abstract representations to be used to characterise extended agent message exchanges has been discussed in the agent community for several years now. However, there is still no consensus on an appropriate formal specification for these abstractions. This paper describes a proposed formalism based on Petri Nets that is to be used for the modelling of complex, concurrent conversations between agents in a multi-agent system. The approach described in this paper can be used both to define simple conversation protocols and to define protocols for more complex conversations composed of a number of simpler conversations. With this method it is possible (a) to capture the concurrent characteristics of a conversation, (b) to capture the state of a complex conversation during runtime, and (c) to reuse a given conversation structure for processing multiple concurrent messages. It is also possible to monitor a conversation and to visualise, both online and off-line, the progress of a conversation. A prototype implementation of a system supporting predefined conversation protocols as Petri Net models developed for the New Zealand Distributed Information Systems research platform is described.