Mamadou D. Seck

Multi-perspective modelling of complex phenomena

This conceptual paper discusses the limitations of a single-perspective hierarchical approach to modelling and proposes multi-perspective modelling as a way to overcome them. As it turns out, multi-perspective modelling is primarily a new methodology, using existing modelling techniques but extending the modelling hierarchy with a new epistemological level which integrates the different perspectives. The methodology will be presented in some detail, and its use will be demonstrated by analyzing an example taken from a socio-political context.

A DEVS component library for simulation-based design of automated container terminals

Modeling and simulation in design processes is traditionally used during the analysis of the future system. However, simulation-based design allows the use of modeling and simulation throughout the synthesis phase which offers greater flexibility to quickly compare alternative designs. In case of container terminals, these alternatives are based on different aspects such as layouts, terminal operating systems, and equipments. Container terminals are characterized by a large number of entity types with multiple instances, interacting in various non-trivial ways. A component-based approach makes the construction of a suitable model easier: the designer can focus on the relevant constructs instead of lower level details. However, much effort is needed to achieve compatibility and modularity between the components. DEVS provides the higher level constructs to conceptualize a complex system independently from the underlying implementation. We present a DEVS component library for container terminal design wherein much attention has been put into the conceptual distinction between control and mechanics. This results in a library that can actively support the design process of containers terminals.

From data to simulation models: component-based model generation with a data-driven approach

Model building is time-consuming and requires expertise in different areas. In this paper, we propose a data-driven approach for automatic model generation using pre-built and validated model components (or building blocks). We view this approach as an automated reuse of model components. Issues such as modularity and composability of model components are addressed. Models can be generated by automatically selecting, structuring and configuring the model components. The formulated rules can be structural and behavioral, by which a relational representation of the desired model composite structure is incrementally constructed. An example of generating a rail network model is given to demonstrate the steps.

The simulation-based multi-objective evolutionary optimization (SIMEON) framework

Simulation and optimization have been successfully combined to solve real-world decision making problems. However, there is no formal structure to define the integration between simulation and optimization. This deters the development of simulation-based optimization methods that have a proper balance between the desired features (i.e. generality, efficiency, high-dimensionality and transparency). This research provides two contributions to the problem above by providing: 1) the design of the framework that facilitates the fulfillment of the aforementioned features; 2) the implementation of the framework in Java. The proposed framework is developed based on Zeiglers modeling and simulation framework and the phases of an optimization study in operations research. The test and evaluation show that the desired features are successfully satisfied.

Applying a model driven approach to component based modeling and simulation

Hierarchical component based modeling and simulation holds great promise, especially in terms of modeling efficiency and model reuse. However, in practice, the approach has not yet lived to its potential. After a diagnosis of this state of affairs, a solution inspired from model driven engineering is proposed. The basic architecture of the framework is explained, based on meta-models, models, and their respective relations. Finally a usage workflow is provided, describing how the framework can be used by different actors within a simulation lifecycle.

Model Continuity in Discrete Event Simulation: A Framework for Model-Driven Development of Simulation Models

Most of the well-known modeling and simulation (M&S) methodologies state the importance of conceptual modeling in simulation studies, and they suggest the use of conceptual models during the simulation model development process. However, only a limited number of methodologies refers to how to move from a conceptual model to an executable simulation model. Besides, existing M&S methodologies do not typically provide a formal method for model transformations between the models in different stages of the development process. Hence, in the current M&S practice, model continuity is usually not fulfilled. In this article, a model-driven development framework for M&S is presented to bridge the gap between different stages of a simulation study and to obtain model continuity. The applicability of the framework is illustrated with a prototype modeling environment and a case study in the discrete event simulation domain.

A context-based multi-perspective modeling and simulation framework

Constantly increasing complexity of organizational environments and changing demands of the stakeholders severely affects the strategic capabilities of organizations and reduces their decision making ability dramatically. Large-scale complex systems like energy grids, air-ground traffic control systems and logistics systems are designed in multi-actor environments and hence require various perspectives (e.g. financial, operational, and environmental) to serve different actors. Although this is the case, current simulation based decision support environments lack the capability of covering multiple system perspectives at once and in different levels of details to provide better understanding of the systems. In this paper, the key challenges and preliminary design ideas are discussed to provide a multiresolution modeling capability. We introduce a context-based ‘view’ concept as an enabler to support multi-perspective modeling in multi-actor environments.

A metamodel and a DEVS implementation for component based hierarchical simulation modeling

Component based hierarchical simulation is based on having pre-built, validated simulation model components that can be coupled to form a composed model that represents a system. The component based approach promises reuse of interoperable components and rapid development. Although component based simulation looks like a promising field and the theory originates more than 20 years ago, many studies do not seem to deliver on the promises, and many simulation projects face problems when reusing existing components in practice. In order to provide reusability and interoperability, it is useful to have generic model definitions that are independent from the implementation details. This means that we need to pay attention to conceptual modeling. The conceptual model is a key concept that forms a bridge between the modelers and the developers, but unfortunately there is no commonly accepted conceptual modeling technique for hierarchical simulation. This paper introduces a metamodel for component based hierarchical simulation and initiates a study of defining a formal component based conceptual modeling technique to overcome the problems in hierarchical simulation. This paper also presents a prototype of a simulation model design environment with a Java interpreter which transforms the visual simulation models into DEVS models.

Modeling the global freight transportation system: a multi-level modeling perspective

The interconnectedness of different actors in the global freight transportation industry has rendered such a system as a large complex system where different sub-systems are interrelated. On such a system, policy-related-exploratory analyses which have predictive capacity are difficult to perform. Although there are many global simulation models for various large complex systems, there is unfortunately very little research aimed to develop a global freight transportation model. In this paper, we present a multi-level framework to develop an integrated model of the global freight transportation system. We employ a system view to incorporate different relevant sub-systems and categorize them in different levels. The four-step model of freight transport is used as the basic foundation of the framework proposed. In addition to that, we also present the computational framework which adheres to the high level modeling framework to provide a conceptualization of the discrete-event simulation model which will be developed.

Libros-II: railway modeling with devs

The increasing complexity of railway systems and the high costs incurred by design and operational errors make modeling and simulation a popular methodology in the domain of railway transportation. To successfully support detailed design and operation, a microscopic rail network model is often deemed not only suitable but also mandatory. However, the simulation of large-scale microscopic models is computationally intensive, making it unsuitable for real-time applications. In this paper, a railway simulation library, LIBROS-II, is introduced which offers high performance rail simulation at the microscopic level. The library is specified with the DEVS formalism. Its major components and their specifications are presented. Its performance is assessed through a simple example and contrasted with a typical model using a continuous modeling abstraction of train movement. The result shows that with comparable model detail and accuracy the LIBROS-II model yields a higher performance than the model using differential equations.