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This paper presents the Process for Agent Specification, Simulation and Implementation (PASSIM), a simulation-based development process for Multi-agent Systems (MASs), which was obtained by integrating the well-known and established Process for Agent Societies Specification and Implementation (PASSI) methodology and a Statecharts-based simulation methodology supporting functional and nonfunctional validation of the MAS being developed. PASSIM can be effectively used as an experimental tool in the context of Agent-Oriented Software Engineering (AOSE) for evaluating the benefits of using simulation for MAS development. To exemplify this process and demonstrate its effectiveness, a case study concerning the analysis, design and simulation of a complex MAS implementing an agent-based e-marketplace is defined and detailed.

Content distribution networks (CDNs) are the most adopted solution for an efficient content delivery over the Internet. They are usually based on caching content, originally produced and stored in origin servers, into surrogate servers which are closer to final users so as to improve the average user perceived latency related to content requests. To further improve the performance of CDNs, new caching techniques should be designed which are not limited to stand-alone surrogate servers but involve coordination among a set of surrogate servers. In this paper we therefore propose the design and evaluation of several distributed architectures for clustering surrogate server: master/slave, multicast-based and peer-to-peer. An agent-oriented modeling and simulation methodology is exploited to model and evaluate the proposed architectures in significant scenarios. The results obtained from simulation show that the designed surrogate clustering architectures allow to improve performance with respect to caching techniques of conventional CDNs.

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