SIMULATION: Transactions of The Society for Modeling and Simulation International

Traoré, Mamadou Kaba

doi: 10.1177/0037549712470058pmid: N/A

Bonaventura, Matías; Wainer, Gabriel A; Castro, Rodrigo

doi: 10.1177/0037549711436267pmid: N/A

We introduce CD++Builder, an open-source environment that aims at providing easy-to-use graphical modeling tools to simplify the construction of models and the execution of simulations of complex Discrete Event System Specification (DEVS) models. The architecture and implementation of CD++Builder focuses on providing simple definition and reuse of components, offering easy extensibility to support new features. CD++Builder includes graphical editors for DEVS-coupled models, DEVS-Graphs and C++ atomic models; it provides code templates that are synchronized with their graphical versions, and it greatly simplifies the software installation and update procedures. We show how this environment can be used to build and simulate DEVS models, and we compare the process with previous versions and other simulation tools, showing that CD++Builder can improve model development by creating DEVS models in a completely assisted manner, including advanced graphical interfaces.

Hong, Su-Youn; Kim, Tag Gon

doi: 10.1177/0037549712450361pmid: N/A

Multi-resolution modeling (MRM) represents a real system as a set of models of different resolutions, at different abstraction levels, from the viewpoint of simulation objectives. MRM is a significant technology for complex and large-scale simulation. However, previous research is almost application specific and dependent on a specific simulation algorithm. The concepts separate multi-resolution models from the simulation models, thereby making them adaptable to any existing simulation methodology. This paper proposes a specification of multi-resolution modeling space (MRMS) for multi-resolution system simulation. The proposed specification is based on concepts of decoupling MRM and multi-resolution simulation. This MRMS specification supports MRM in two parts: resolution conversion for dynamically changing simulation model structures and resolution matching interfaces between events in different resolutions. A simple example demonstrates advantages of the proposed specification.

Saadawi, Hesham; Wainer, Gabriel

doi: 10.1177/0037549711424424pmid: N/A

Real-time systems modeling and verification is a complex task. In many cases, formal methods have been employed to deal with the complexity of these systems, but checking those models is usually unfeasible. Modeling and simulation methods introduce a means of validating these model’s specifications. In particular, Discrete Event System Specification (DEVS) models can be used for this purpose. Here, we introduce a new extension to the DEVS formalism, called the Rational Time-Advance DEVS (RTA-DEVS), which permits modeling the behavior of real-time systems that can be modeled by the classical DEVS; however, RTA-DEVS models can be formally checked with standard model-checking algorithms and tools. In order to do so, we introduce a procedure to create timed automata (TA) models that are behaviorally equivalent to the original RTA-DEVS models. This enables the use of the available TA tools and theories for formal model checking. Further, we introduce a methodology to transform classic DEVS models to RTA-DEVS models, thus enabling formal verification of classic DEVS with an acceptable accuracy.

Cicirelli, Franco; Furfaro, Angelo; Nigro, Libero

doi: 10.1177/0037549711434603pmid: N/A

Timing requirements are important aspects in workflow modelling, analysis and enactment. In the last few years, though, many workflow languages and tools have been proposed but only few of them address timing issues during enactment. This paper shows that time stream Petri nets (TSPNs), originally designed for multimedia/hypermedia modelling and analysis, are a well-suited formalism also for supporting the whole lifecycle of workflow processes with timing constraints. A novel approach to modelling, analysis and distributed enactment of workflow processes specified by TSPNs is proposed. Functional and temporal properties of a TSPN model can be checked using exhaustive verification or a DEVS-based simulation tool. Enactment rests on PN-Engine, a decentralized enactment engine based on the service-oriented computing paradigm, which enables execution of workflow processes where the coordinated activities may involve cross-boundary organizations. The approach is illustrated by means of a modelling example concerned with a wine-production process.

Errampalli, Madhu; Okushima, Masashi; Akiyama, Takamasa

doi: 10.1177/0037549712443716pmid: N/A

Microscopic traffic simulation (MTS) has attracted increasing attention in the last two decades as it analyzes individual vehicle/driver behavior more precisely and realistically than other methods. MTS is nothing but a series of human decisions under various traffic situations. Since human element is involved at many stages of simulation, the possibility of approximation/error in the decisions would be high. In this direction, the fuzzy logic technique appropriately takes such approximations into account while modeling drivers’ decisions. Some of the MTS models have considered fuzzy logic in at most one or two models, such as car following, lane change behavior, etc., with limited urban congested conditions. However, human involvement exists beyond these and realistic output from the simulation would not be possible unless the approximations involved at different stages are appropriately and simultaneously considered. In the present study, a Fuzzy Logic based Microscopic Traffic Simulation Model (FLoMiTSiM) to describe human behavior on the urban road network in many possible situations is proposed and appropriately validated using the observed data from the city of Gifu, Japan. To demonstrate the applicability and suitability of the proposed FLoMiTSiM, bus priority policies, namely bus lanes, are evaluated.

Bharathy, Gnana K; Silverman, Barry

doi: 10.1177/0037549712446854pmid: N/A

The philosophical perspectives on model evaluation can be broadly classified into reductionist/logical positivist and relativist/holistic. In this paper, we outline some of our past efforts in, and challenges faced during, evaluating models of social systems with cognitively detailed agents. Owing to richness in the model, we argue that the holistic approach and consequent continuous improvement are essential to evaluating complex social system models such as these. A social system built primarily of cognitively detailed agents can provide multiple levels of correspondence, both at observable and abstract aggregated levels. Such a system can also pose several challenges, including large feature spaces, issues in information elicitation with database, experts and news feeds, counterfactuals, fragmented theoretical base, and limited funding for validation. We subscribe to the view that no model can faithfully represent reality, but detailed, descriptive models are useful in learning about the system and bringing about a qualitative jump in understanding of the system it attempts to model – provided they are properly validated. Our own approach to model evaluation is to consider the entire life cycle and assess the validity under two broad dimensions of (1) internally focused validity/quality achieved through structural, methodological, and ontological evaluations; and (2) external validity consisting of micro validity, macro validity, and qualitative, causal and narrative validity. In this paper, we also elaborate on selected validation techniques that we have employed in the past. We recommend a triangulation of multiple validation techniques, including methodological soundness, qualitative validation techniques, such as face validation by experts and narrative validation, and formal validation tests, including correspondence testing.