This paper proposes an agent infrastructure (Theatre) centered on Java for distributed simulations over High-Level Architecture/RunTime Infrastructure (HLA/RTI). The architecture rests on actors (agents) as the basic building blocks. Actors have a public message interface and encapsulate a state of local variables and a behavior patterned as a finite state machine. Actors interact with one another by asynchronous message passing. At the system level, theatres are used as the execution platforms for actors. Theatres naturally map on to HLA federates. Actors can migrate between theatres for load-balancing concerns, or in response to (re)configuration operations of dynamic structure systems. The paper introduces Theatre and demonstrates its application to a complex simulation model based on unmanned aerial vehicles (UAVs). The case study is an open agent-based distributed model where mobile agents follow communication patterns established at runtime.
This work centres on a control framework for general multi-agent systems, which separates the design of agents behaviours (the application layer) from crosscutting control concerns (the control layer) regulating message exchange and processing. The goal is to support modelling and execution of a multi-agent system whose evolution is transparently governed by a pluggable control structure. A library of different control structures, including pure-concurrent and time-sensitive (real-time and simulation) strategies, was developed. The paper describes the developed control framework and focusses on the achievement of control strategies compliant with agent mobility and resource availability. The control design rests on a minimal actor computational model extended with actions, which are independent computational tasks able to execute in parallel. The approach enables model continuity, that is, the same model is used from analysis by simulation to implementation and real-time execution. The framework is prototyped on top of the JADE agent infrastructure. Usability and effectiveness of the resultant approach are demonstrated by a case study based on a complex closed queue network of services. On-going and future work is finally pointed out in the conclusions.
3334F. CICIRELLI AND L. NIGRO sidering the availability of dedicated processing units. Flexibility of control design is also advocated to deal with problems of mechanism design [2] where a suitable control strategy is required to regulate/coordinate the decision process in a group of agents during the allocation of scarce resources. This paper proposes an original and flexible control framework for distributed multi-agent systems. The approach makes it possible to transparently aggregate a given control module extracted from a library to a multi-agent system. One of the challenging goals in this work is to support model continuity [3] whose aim is to favour the use of a same model from property analysis (possibly based on parallel/distributed simulation) to real-time execution. A particular implementation of the approach, devoted to the schedulability analysis of real-time systems, is described in [4].The proposed control framework purposely depends on a minimal computational actor model [5][6][7]. The actor model actually used in this paper is novel in that it owns a notion of actions, which are a key for transparently switching from simulation to real execution. Actions naturally map on to processing units (PUs) managed by a given control strategy. PUs model computational resources of the external environment of the application. Both the availability and the behaviour of processing units can affect, in an orthogonal way, the execution of the application. In particular, the evolution of a realized multi-agent system constitutes an emerging property of the interaction between the application and its environment, mediated by the provided control layer.For demonstration purpose, the framework is prototyped in JADE [8, 9]. JADE was chosen because it is a representati...
IP multicast has fueled an assortment of large-scale applications over the Internet ranging from interactive video conferencing to whiteboards to video recording on-demand systems. Such applications are mainly based on the lightweight session model and on Internet standard protocols. In particular, video recording on-demand systems allow a remote client to request (i) recording of an advertised multimedia session and (ii) playback of sessions previously archived. They are primarily designed for serving the needs of a single user wishing, for instance, to watch a movie or to attend a recorded seminar. No groupware support is normally offered. As an example, a number of remotely located classmates, that belong to the same academic course, can access a media server containing archived course lessons, select a lesson and go over it collaborating with each other. In this paper, we introduce the cooperative playback systems, which enable explicitly grouped users to jointly work and cooperatively control playbacks of on-demand multimedia sessions. We also present a multicast control streaming protocol based on an extension of RTSP adapted on top of LRMP, and illustrate our Java-enabled cooperative playback system, ViCRO C .
This work is concerned with modelling, analysis and implementation of embedded control systems using RT-DEVS, i.e. a specialization of classic discrete event system specification (DEVS) for real-time. RT-DEVS favours model continuity, i.e. the possibility of using the same model for property analysis (by simulation or model checking) and for real time execution. Special case tools are reported in the literature for RT-DEVS model analysis and design. In this work, temporal analysis of a model exploits a translation in Uppaal timed automata for exhaustive verification. For large models a simulator was realized in Java which directly stems from RT-DEVS operational semantics. The same concerns are at the basis of a real-time executive. The paper describes the proposed RT-DEVS development methodology and clarifies its implementation status. The approach is demonstrated by applying it to an embedded system example which is analyzed through model checking and implemented in Java. Finally, research directions which deserve further work are indicated.
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