Modelling and Analysing the Contract Net Protocol - Extension Using Coloured Petri Nets

The Contract Net Protocol is a task allocation protocol that facilitates negotiation between bidders and an auctioneer in a MultiAgent System to form a contract. The extension allows the bidders to interact with more than one auctioneer concurrently, and to update their bids until a bid is granted. This introduces flexibility and ensures better selection of a bid. In this paper, we model the Contract Net Protocol extension with Coloured Petri Nets and show that it terminates correctly. We analyse the terminal states and prove that the agents have consistent beliefs at the end of the negotiations, and that there is no “dead code” in the procedures. Lastly, we show how the number of terminal states and channel bounds are related to the number of bidders.