Giving Life to Agent Interactions

Agent UML (AUML) is an extension of the standard objectoriented modelling language UML adapted for agent-based systems. In AUML sequence diagrams are extended to describe specific dynamic aspects of agents including dynamic role assignment, nondeterministic choice in agent decisions and concurrent communication. These diagrams are used to describe agent interaction protocols. We describe some of the problems of extended sequence diagrams in AUML. Not all of these problems are specific to agent sequence diagrams and have been previously identified in UML’s sequence diagrams and Message Sequence Charts (MSCs). Live Sequence Charts (LSCs) are a very expressive extension of MSCs that addresses many of these issues in the context of objectoriented systems. We propose an extension of LSCs for agents and show how it is useful for modelling agent interactions, agent commitments, agent society norms and forbidden behaviour. LSCs have the expressiveness of temporal logic and we show how from an LSC we can derive formulae in a simplified variant of the branching time distributed temporal logic Mdtl.