Hessam S. Sarjoughian

A layered modeling and simulation architecture for agent-based system development

The paper proposes a layered architectural framework to support agent based system development in a collaborative, multidisciplinary engineering setting. This architecture is viewed from two distinct perspectives. First, the environment must enable agent based modeling and simulation. Second, it should support concurrent (team oriented) engineering. The main focus is on the proposed layered architecture delineating various needs of an agent based system, thus supporting incremental specification design, implementation, and testing. In our discussions, we distinguish between performing agents and simulated agents. The former refers to agents as they are performing their tasks in real-world settings. The latter refers to agents that have their behavior simulated in a virtual environment. In these terms, the proposed framework is intended to form the basis for environments that support development of agents, in both performance and simulation modes, as well as in hybrid combination (both performing and simulated agents interacting at the same time). The proposed framework is a step toward realization of agent based systems under the umbrella of the simulation based acquisition (SBA) initiative of the US Department of Defense.

CoSMoS: a visual environment for component-based modeling, experimental design, and simulation

An integrated modeling and simulation tool called Component-based System Modeler and Simulator (CoSMoS) is developed. It supports visual development of families of models that have well-defined logical specifications. The logical component-based models persist in relational databases and may be automatically translated into specific target simulation and markup programming languages. The underlying system-theoretic modeling framework of CoSMoS lends itself for the well-known discrete-time, continuous, and discrete-event modeling approaches. Currently, CoSMoS supports developing parallel DEVS-compliant models which can be executed using the DEVS-Suite simulator. The underlying process lifecycle of the CoSMoS enables systematic transitioning from visual model development and design of experiments to simulation execution and experimentation. Simulation data can be used for run-time animation and viewing of time-based trajectories or exported for post processing. This tool helps to simplify simulation-based system design, verification, and validation. The core capabilities of the CoSMoS are exemplified with a conceptual model of an anti-virus network software system.

A simulation framework for service-oriented computing systems

An SOA-compliant DEVS (SOAD) simulation framework is proposed for modeling service-oriented computing systems. A set of novel abstract component models that conform to the SOA principles and are grounded in the DEVS formalism is developed. The approach supports construction of hierarchical composition of service models with feedback relationships. A SOAD Simulator (SOADS) is designed and implemented. An exemplar model of a basic service-oriented computing system is described. A representative experiment capturing throughput and timeliness QoS attributes for the exemplar model is devised, simulated, and described. The paper concludes with the concept of community-based development of the SOAD framework and tools.

Toward Development of Adaptive Service-Based Software Systems

The rapid adoption of service-oriented architecture (SOA) in many large-scale distributed applications requires the development of adaptive service-based software systems (ASBS) with the capability of monitoring the changing system status, analyzing, and controlling tradeoffs among various quality-of-service (QoS) aspects, and adapting service configurations to satisfy multiple QoS requirements simultaneously. In this paper, our results toward the development of adaptive service-based software systems are presented. The formulation of activity-state-QoS (ASQ) models and how to use the data from controlled experiments to establish ASQ models for capturing the cause-effect dynamics among service activities, system resource states, and QoS in service-based systems are presented. Then, QoS monitoring modules based on ASQ models and SOA-compliant simulation models are developed to support the validation of the ASBS design. The main idea for developing QoS adaptation modules based on ASQ models is discussed. An experiment based on a voice communication service is used to illustrate our results.

Exploiting HLA and DEVS To Promote Interoperability and Reuse in Lockheed's Corporate Environment

Joint MEASURE™ (Mission Effectiveness Analysis Simulator for Utility, Research and Evaluation) demonstrates the effective applica tion of HLA-compliant simulation outside the traditional realm of training to analytic studies of mission effectiveness of systems within larger systems of systems configurations. This paper discusses how Joint MEASURE effectively ex ploits both the DEVS modeling and HLA simu lation frameworks to support high performance distributed simulation and thereby, to overcome impediments to interoperability and reuse of Lockheeds models arising from the reluctance of groups to share their code at the source level with others within the corporation.

A co-design modeling approach for computer network systems

Co-design modeling is considered key toward handling the complexity and scale of network systems. The ability to separately specify the software and hardware aspects of computer network systems offers new capabilities beyond what is supported in modeling frameworks and tools such as NS-2 and OPNET. The DEVS/DOC simulation environment supports logical co-design specification based on the distributed object computing (DOC) abstract model. To overcome DEVS/DOCs lack of support for visual and persistent modeling, this paper presents SESM/DOC, a novel approach, which is based on the scaleable entity structure modeler (SESM), a component-based modeling framework. This approach supports logical, visual and persistent modeling. Modelers can develop software and hardware models separately and systematically integrate them to specify a family of computer network system designs. This paper details the SESM/DOC co-design modeling approach with the help of a search engine system example, and presents a discussion for future research directions.

Hybrid discrete event simulation with model predictive control for semiconductor supply-chain manufacturing

Simulation modeling combined with decision control can offer important benefits for analysis, design, and operation of semiconductor supply-chain network systems. Detailed simulation of physical processes provides information for its controller to account for (expected) stochasticity present in the manufacturing processes. In turn, the controller can provide (near) optimal decisions for the operation of the processes and thus handle uncertainty in customer demands. In this paper, we describe an environment that synthesizes discrete-event system specification (DEVS) with model predictive control (MPC) paradigms using a knowledge interchange broker (KIB). This environment uses the KIB to compose discrete event simulation and model predictive control models. This approach to composability affords flexibility for studying semiconductor supply-chain manufacturing at varying levels of detail. We describe a hybrid DEVS/MPC environments via a knowledge interchange broker. We conclude with a comparison of this work with another that employs the Simulink/MATLAB environment.

Software and Simulation Modeling for Real-Time Software-Intensive Systems

Successful development of large-scale complex and distributed real-time systems commonly relies on models developed separately for simulation studies and software implementation. Systems theory provides sound modeling principles to characterize structural and behavioral aspects of systems across time and space. The behavior of these models can be observed using simulation protocols that can correctly interpret time-based logical dynamics. Similarly, object-orientation theories and software architecture principles enable modeling static and dynamic behavior of systems. While models described either in system-theoretic or object-orientated languages may be used for both software design and simulation modeling, each has its own strengths and weaknesses. For example, a class of system-theoretic modeling approach called Discrete-event System Specification (DEVS) provides an appropriate basis to develop simulation models exhibiting concurrent and distributed behavior. Similarly, the Unified Modeling Language with real-time (UML-RT) constructs can be used to develop software design models that can be implemented and executed. Since software models are not suitable to be used as simulation models and simulation models may not adequately lend themselves to serve as software design blueprints, it is important to examine these approaches. We show some of the key shortcomings of these simulation and software design modeling approaches by developing some detailed specifications and implementation of a coffee machine with a focus on their treatment of logical and physical time.

Design and implementation of distributed real-time DEVS/CORBA

In this paper the design and implementation of Distributed Real-Time DEVS/CORBA is discussed as an extension of previously developed DEVS-based modeling and simulation frameworks. The major objective in developing Distributed Real-Time DEVS/CORBA is to establish a framework in which the distributed real-time systems can be designed through DEVS-based modeling and simulation studies, and then migrated with minimal additional effort to be executed in the real-time distributed environment. This environment will provide generic support for developing models of distributed embedded software systems, evaluating their performance and timing behavior through simulation and easing the transition from simulation to actual executions In this paper we describe detailed design and implementation aspects of the environment which was implemented over Visibroier CORBA middleware and ACE/TAO real-time CORBA services.

Simulation of Semiconductor Manufacturing Supply-Chain Systems With DEVS, MPC, and KIB

The dynamics of high-volume discrete-part semiconductor manufacturing supply-chain systems can be described using a combination of Discrete EVent System Specification (DEVS) and model predictive control (MPC) modeling approaches. To formulate the interactions between the discrete process model and its controller, another model called Knowledge Interchange Broker (KIB) is used. A robust and scalable testbed supporting DEVS-based manufacturing process modeling, MPC-based controller design, and the KIBDEVS/MPC interaction model is developed. A suite of experiments have been devised and simulated using this testbed. The flexibility of this approach for modeling, simulating, and evaluating stochastic discrete process models under alternative control schemes is detailed. The testbed illustrates the benefits and challenges associated with developing and using realistic manufacturing process models and process control policies. The simulation environment demonstrates the importance of explicitly defining and exposing the interactions between the manufacturing and control subsystems of complex semiconductor supply-chain systems.