Browsing by Author "Zeigler, Bernard P."

Now showing 1 - 4 of 4
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    Conjoining Wymore’s Systems Theoretic Framework and the DEVS Modeling Formalism: Toward Scientific Foundations for MBSE
    Wach, Paul; Zeigler, Bernard P.; Salado, Alejandro (MDPI, 2021-05-27)
    The objective of this research article is to re-introduce some of the concepts provided by A. Wayne Wymore in his mathematical theory of Model-Based Systems Engineering, discuss why his framework might have not been adopted, and define a potential path to modernize the framework for practical application in the digital age. The dense mathematical theory has never been converted to a practical form. We propose a path to modernization by creating a metamodel of Wymore’s mathematical theory of MBSE. This enables explaining the concepts in simple to understand terms and shows the internal consistency provided by the theory. Furthermore, the metamodel allows for conversion of the theory into software application, for which we show some initial results that open the research to the art of the possible. In recognition of limitation of the theory, we make the case for a merger of the theoretical framework with the enhanced formalism of Discrete Event System Specification (DEVS). This will establish a path toward the scientific foundations for MBSE to enable future implementations of the complementary pairing and their empirical results.
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    Integrated Model Pluralism: An Alternative to a Universal Model Description Language
    Zeigler, Bernard P. (Department of Computer Science, Virginia Polytechnic Institute & State University, 1979)
    This paper elaborates an integrated hierarchy of model description formalisms previously proposed. We discuss the advantages of the hierarchical approach vis a vis a standardized universal model description language. Among the principal advantages are the opportunities provided for concise model specification while at the same time enabling equivalence testing of models expressed in diverse formalisms.
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    Model specification and analysis for discrete event simulation
    Overstreet, C. Michael (Virginia Polytechnic Institute and State University, 1982)
    Several authors assert that any significant improvement in the efficiency in the development and utilization of simulation models requires the assistance of a Model Management System to automate much of the process. This work develops one aspect of such system: tools fundamental to the specification and analysis of discrete event models. A model specification language is developed which allows analysis of a model specification as the specification is being developed. Model analyses are discussed which (1) detect several types of errors in a model specification, (2) automate the generation of many types of documentation useful during model development and the generation of model documentation useful during the model life cycle, (3) improve model implementations by assisting in the choice of a world view and implementation technique. A model specification in this language is called a condition specification (CS). Formal procedures are developed to transform a cs into a model specification in any of the three traditional worldviews of event scheduling, activity scanning, and process interaction. These transformation procedures are supported by a careful definition of the equivalency of model specifications and by a characterization of each of the three world views. Results are proved which show that the approach of each worldview transformation is valid (i.e., result in equivalent model specifications). This is necessary since the transformation procedures may delete parts of a CS. Both the characterization of each world view and the procedures that transform a cs into each world view provide a better understanding of the nature of each worldview than has existed to date. Several necessary properties for error-free model specifications are identified and defined. While useful test procedures for these properties can be developed, most of these properties are shown to be unverifiable in an absolute sense. That is, it is proved that no algorithm is possible which can detect every instance of several important model specification errors.
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    Study of Equivalence in Systems Engineering within the Frame of Verification
    Wach, Paul F. (Virginia Tech, 2023-01-20)
    This dissertation contributes to the theoretical foundations of systems engineering (SE) and exposes an unstudied SE area of definition of verification models. In practice, verification models are largely qualitatively defined based on heuristic assumptions rather than science-based approach. For example, we may state the desire for representativeness of a verification model in qualitative terms of low, medium, or high fidelity in early phases of a system lifecycle when verification requirements are typically defined. Given that fidelity is defined as a measure of approximation from reality and that the (real) final product does (or may) not exist in early phases, we are stating desire for and making assumptions of representative equivalence that may not be true. Therefore, this dissertation contends that verification models can and should be defined on the scientific basis of systems theoretic principles. Furthermore, the practice of SE is undergoing a digital transformation and corresponding desire to enhance SE educationally and as a discipline, which this research proposes to address through a science-based approach that is grounded in the mathematical formalism of systems theory. The maturity of engineering disciplines is reflected in their science-based approach, such as computational fluid dynamics and finite element analysis. Much of the discipline of SE remains qualitatively descriptive, which may suffer from interpretation discrepancies; rather than being grounded in, inherently analytical, theoretical foundations such as is a stated goal of the SE professional organization the International Council on Systems Engineering (INCOSE). Additionally, along with the increased complexity of modern engineered systems comes the impracticality of verification through traditional means, which has resulted in verification being described as broken and in need of theoretical foundations. The relationships used to define verification models are explored through building on the systems theoretic lineage of A. Wayne Wymore; such as computational systems theory, theory of system design, and theory of problem formulation. Core systems theoretic concepts used to frame the relationship-based definition of verification models are the notions of system morphisms that characterize equivalence between pairs, problem spaces of functions that bound the acceptability of solution systems, and hierarchy of system specification that characterizes stratification. The research inquisition was in regard to how verification models should be defined and hypothesized that verification models should be defined through a combination of systems theoretic relationships between verification artifacts; system requirements, system designs, verification requirements, and verification models. The conclusions of this research provide a science-based metamodel for defining verification models through systems theoretic principles. The verification models were shown to be indirectly defined from system requirements, through system designs and verification requirements. Verification models are expected to be morphically equivalent to corresponding system designs; however, there may exist infinite equivalence which may be reduced through defining bounding conditions. These bounding conditions were found to be defined through verification requirements that are formed as (1) verification requirement problem spaces that characterize the verification activity on the basis of morphic equivalence to the system requirements and (2) morphic conditions that specify desired equivalence between a system design and verification model. An output of this research is a system theoretic metamodel of verification artifacts, which may be used for a science-based approach to define verification models and advancement of the maturity of the SE discipline.