Representing Conversations for Scalable Overhearing

Abstract

Open distributed multi-agent systems are gaining interest in the academic community and in industry. In such open settings, agents are often coordinated using standardized agent conversation protocols. The representation of such protocols (for analysis, validation, monitoring, etc) is an important aspect of multi-agent applications. Recently, Petri nets have been shown to be an interesting approach to such representation, and radically different approaches using Petri nets have been proposed. However, their relative strengths and weaknesses have not been examined. Moreover, their scalability and suitability for different tasks have not been addressed. This paper addresses both these challenges. First, we analyze existing Petri net representations in terms of their scalability and appropriateness for overhearing, an important task in monitoring open multi-agent systems. Then, building on the insights gained, we introduce a novel representation using Colored Petri nets that explicitly represent legal joint conversation states and messages. This representation approach offers significant improvements in scalability and is particularly suitable for overhearing. Furthermore, we show that this new representation offers a comprehensive coverage of all conversation features of FIPA conversation standards. We also present a procedure for transforming AUML conversation protocol diagrams (a standard humanreadable representation), to our Colored Petri net representation.

Petri Net Plans

“…Interactions among agents have also been modeled by PNs in the literature, with a special focus on the formal modeling of conversations using colored PNs [8]. A substantial comparative review of the different approaches, including a colored PN model of multi-agent conversations, where places explicitly represent joint interaction states and messages, can be found in [25]. Poutakidis et al [43] introduced interaction protocols, specified using Agents UML and translated to PNs, to debug agent interaction.…”

A framework for facilitating cooperation in multi-agent systems

“…Gutnik et al [15] proposed a CPN-based representation for overhearing, where an overhearing agent passively tracked many concurrent conversations involving multiple participants based on their exchanged messages. In their work places represent valid joint conversation states and messages, and token colour was used to distinguish concurrent conversations.…”

Collaboration among a satellite swarm

“…They may be represented in a variety of ways, e.g. AUML [32] or Petri-nets [23]. As protocols are originally designed for a single goal, some works aim at endowing them with flexibility [8,26].…”