A supply chain comprises several different kinds of actors that interact either in an ad hoc fashion (e.g. an eventual deal) or in a previously well-planned way. In the latter, how the interactions develop is described in contracts that are agreed on before the interactions start. This agreement may involve several partners, thus a multi-party contract is better suited than a set of bi-lateral contracts. If one is willing to negotiate automatically such kind of contracts, an appropriate negotiation protocol should be at hand. However, the ones for bi-lateral contracts are not suitable for multi-party contracts, e.g. the way to achieve consensus when only two negotiators are haggling over some issues is quite different if there are several negotiators involved. In the first case, a simple bargain would suffice, but in the latter a ballot process is needed. This paper briefly presents our negotiation protocol for electronic multi-party contracts which seamlessly combines several negotiation styles. It also elaborates on the main negotiation patterns the protocol allows for: bargain (for peer-to-peer negotiation), auction (when there is competition among the negotiators) and ballot (when the negotiation aims at consensus) and presents other patterns that can be built on these basic ones. Finally, it describes an implementation of this protocol based on Web services, and built on the YAWL Workflow Management System. © 2011 World Scientific Publishing Company.203221259Min, H., Zhou, G., Supply chain modeling: Past, present and future (2002) Computers and Industrial Engineering, 43 (1-2), pp. 231-249. , DOI 10.1016/S0360-8352(02)00066-9, PII S0360835202000669Bacarin, E., Madeira, E.R.M., Medeiros, C.B., Contract e-negotiation in agricultural supply chains (2008) Int. Journal of Electronic Commerce, 12 (4), pp. 71-97Bacarin, E., Madeira, E.R.M., Medeiros, C.B., Assembling and managing virtual organizations out of multi-party contracts (2009) ICEIS, pp. 758-769Van Der Aalst, W.M.P., Ter Hofstede, A.H.M., Kiepuszewski, B., Barros, A.P., Workflow patterns (2003) Distributed and Parallel Databases, 14 (1), pp. 5-51Ter Hofstede, A.H.M., Van Der Aalst, W.M.P., Adams, M., Russell, N., (2010) Modern Business Process Automation: YAWL and Its Support Environment, , Springer-Verlag, BerlinVan Der Aalst, W.M.P., Ter Hofstede, A.H.M., YAWL: Yet another workflow language (2005) Information Systems, 30 (4), pp. 245-275. , DOI 10.1016/j.is.2004.02.002, PII S0306437904000304Aalst Der Van, P.W.M., The application of petri nets to workflow management (1998) The Journal of Circuits, Systems and Computers, 8 (1), pp. 21-66Aalst Der Van, P.W.M., Aldred, L., Dumas, M., Ter Hofstede, A.H.M., Design and implementation of the YAWL system (2004) Advanced Information Systems Engineering, Proceedings of the 16th International Conference on Advanced Information Systems Engineering (CAiSE'04 ), 3084, pp. 142-159. , eds. A. Persson and J. Stirna, Lecture Notes in Computer Science, (Springer-Verlag, Berlin)Bacarin, E., Madeira, E.R.M., Medeiros, C.M.B., (2009) Spica's Multi-party Negotiation Protocol: Implementation Using Yawl. Technical Report IC-09-44, , Institute of Computing/UNICAMP, MarchBacarin, E., Van Der Aalst, W.M.P., Madeira, E., Medeiros, C.B., Towards modeling and simulating a multi-party negotiation protocol with colored petri nets (2007) Proc. CPN 07 - 8th Workshop and Tutorial on Practical Use of Coloured Petri Nets and the CPN ToolsArshinder, Kandan, A., Deshmukh, S.G., A framework for evaluation of coordination by contracts: A case of two-level supply chains (2009) Computer & Industrial Engineering, 56 (4), pp. 1177-1191Aalst Der Van, P.W.M., Barros, A.P., Ter Hofstede, A.H.M., Kiepuszewski, B., Advanced workflow patterns (2000) CooplS '00: Proceedings of the 7th International Conference on Cooperative Information Systems, pp. 18-29. , Springer-Verlag, London, UKMulyar, N.A., (2009) Patterns for Process-aware Information Systems: An Approach Based on Colored Petri Nets, , PhD thesis, Technische Universiteit EindhovenFantinato, M., De Toledo, M.B.F., Gimenes S. De, I.M., A feature-based approach to electronic contracts (2006) CEC/EEE'06, pp. 34-41. , IEEE Computer Society, Los Alamitos, CA, USAPanagiotidi, S., Vázquez-Salceda, J., Álvarez Napagao, S., Ortega-Martorell, S., Willmott, S., Confalonieri, R., Storms, P., Intelligent contracting agents language (2008) Proceedings of the Symposium on Behaviour Regulation in Multi-Agent Systems - BRMAS'08, pp. 49-54. , Aberdeen, UK (April)Alberti, M., Chesani, F., Gavanelli, M., Lamma, E., Mello, P., Montali, M., Torroni, P., Expressing and verifying business contracts with abductive logic programming (2008) Int. Journal of Electronic Commerce, 12 (4), pp. 9-38Grosof, B.N., Poon, T.C., SweetDeal: Representing agent contracts with exceptions using semantic web rules, ontologies, and process descriptions (2004) International Journal of Electronic Commerce, 8 (4), pp. 61-97Governatori, G., Dumas, M., Ter Hofstede, A.H.M., Oaks, P., A formal approach to protocols and strategies for (legal) negotiation (2001) ICAIL, pp. 168-177Oren, N., Norman, T.J., Preece, A.D., Argumentation based contract monitoring in uncertain domains (2007) IJCAI, pp. 1434-1439. , ed. Manuela M. VelosoXu, L., A multi-party contract model (2004) SIGecom Exch., 5 (1), pp. 13-23Desai, N., Narendra, N.C., Singh, M.P., Checking correctness of business contracts via commitments (2008) AAMAS '08: Proceedings of the 7th International Joint Conference on Autonomous Agents and Multiagent Systems, pp. 787-794. , Richland, SC, International Foundation for Autonomous Agents and Multiagent SystemsHanson, J.E., Milosevic, Z., Conversation-oriented protocols for contract negotiations (2003) EDOC 00, pp. 40-49Bartolini, C., Preist, C., Jennings, N.R., A software framework for automated negotiation (2005) Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 3390 LNCS, pp. 213-235. , Software Engineering for Multi-Agent Systems III: Research Issues and Practical ApplicationsChiu, D.K.W., Cheung, S.C., Hung, P.C.K., Chiu, S.Y.Y., Chung, A.K.K., Developing e-Negotiation support with a meta-modeling approach in a Web services environment (2005) Decision Support Systems, 40 (1 SPEC. ISS.), pp. 51-69. , DOI 10.1016/j.dss.2004.04.004, PII S0167923604000636Di Noia, T., Di Sciascio, E., Donini, F.M., Mongiello, M., A system for principled matchmaking in an electronic marketplace (2004) International Journal of Electronic Commerce, 8 (4), pp. 9-37Fatima, S.S., Wooldridge, M., Jennings, N.R., Approximate and online multi-issue negotiation (2007) AAMAS, pp. 951-958Kallel, O., Jaâfar, I.B., Dupont, L., Ghédira, K., Multi-agent negotiation in a supply chain - Case of the wholsale price contract (2008) ICEIS, (4), pp. 305-314. , eds. J. Cordeiro and J. FilipeZhang, X., Lesser, V., Meta-level coordination for solving negotiation chains in semicooperative multi-agent systems (2007) AAMAS '07: Proceedings of the 6th International Joint Conference on Autonomous Agents and Multiagent Systems, ACM, pp. 50-57. , New York, NY, USAWeigand, H., Van Den Heuvel, W.-J., Cross-organizational workflow integration using contracts (2002) Decision Support Systems, 33 (3), pp. 247-265. , DOI 10.1016/S0167-9236(02)00015-5, PII S0167923602000155Linington, P.F., Milosevic, Z., Cole, J., Gibson, S., Kulkarni, S., Neal, S., A unified behavioural model and a contract language for extended enterprise (2004) Data & Knowledge Engineering, 51 (1), pp. 5-29Aalst Der Van, P.W.M., Massuthe, P., Stahl, C., Wolf, K., (2007) Multiparty Contracts: Agreeing and Implementing Interorganizational Processes, p. 213. , Technical report, Humboldt-Universitat zu Berlin, Informatik-BerichteUdupi, Y.B., Singh, M.P., Contract enactment in virtual organizations: A commitment-based approach (2006) AAAI, , (AAAI Press)Zuzek, M., Talik, M., Swierczynski, T., Wisniewski, C., Kryza, B., Dutka, L., Kitowski, J., Formal model for contract negotiation in knowledge-based virtual organizations (2008) ICCS 2008, Part III, LNCS 5103, pp. 409-418. , Springer-Verlag, Berlin