Towards Self-Adaptive Discrete Event Simulation (SADES)

Systems that benefit from the ongoing use of simulation, often require considerable input by the modeller(s) to update and maintain the models. This paper proposes automating the evolution of the modelling process for discrete event simulation (DES) and therefore limiting the majority of the human modeller’s input to the development of the model. This mode of practice could be named Self-Adaptive Discrete Event Simulation (SADES). The research is driven from ideas emerging from simulation model reuse, automations in the modelling process, real time simulation, dynamic data driven application systems, autonomic computing and self-adaptive software systems. This paper explores some of the areas that could inform the development of SADES and proposes a modified version of the MAPE-K feedback control loop as a potential process. The expected outcome from developing SADES would be a simulation environment that is self-managing and more responsive to the analytical needs of real systems

Applying the levels of conceptual interoperability model in support of integratability, interoperability, and composability for system-of-systems engineering

The Levels of Conceptual Interoperability Model (LCIM) was developed to cope with the different layers of interoperation of modeling & simulation applications. It introduced technical, syntactic, semantic, pragmatic, dynamic, and conceptual layers of interoperation and showed how they are related to the ideas of integratability, interoperability, and composability. The model was successfully applied in various domains of systems, cybernetics, and informatics

Applying the Levels of Conceptual Interoperability Model in Support of Integratability, Interoperability, and Composability for System-of-Systems Engineering

The Levels of Conceptual Interoperability Model (LCIM) was developed to cope with the different layers of interoperation of modeling & simulation applications. It introduced technical, syntactic, semantic, pragmatic, dynamic, and conceptual layers of interoperation and showed how they are related to the ideas of integratability, interoperability, and composability. The model was successfully applied in various domains of systems, cybernetics, and informatics

An Object-Oriented Framework for Designing Reusable and Maintainable DEVS Models using Design Patterns

Design patterns are well practices to share software development experiences. These patterns allow enhancing reusability, readability and maintainability of architecture and code of software applications. As simulation applies computerized models to produce traces in order to obtain results and conclusions, designers of simulation explored design patterns to make the simulation code more reusable, more readable and easy to maintain, in addition to design complex software oriented simulation modeling. In DEVS (Discrete Event System specification), the designers have successfully designed simulations, frameworks, tools, etc. However, some issues remain still open and should be explored like how a piece of code that implements a set of states, events and transitions may be reused to design a new DEVS model? How may a DEVS model be extended to a new formalism? Etc. In this paper, we address these issues and we propose a set of patterns that may serve as guidelines to designers of DEVS models and its extensions and may contribute to the design of an operational simulation framework. These patterns are inspired partly by the available designs of DEVS community and software engineering developers

An Empirical Survey on Co-simulation: Promising Standards, Challenges and Research Needs

Co-simulation is a promising approach for the modelling and simulation of complex systems, that makes use of mature simulation tools in the respective domains. It has been applied in wildly different domains, oftentimes without a comprehensive study of the impact to the simulation results. As a consequence, over the recent years, researchers have set out to understand the essential challenges arising from the application of this technique. This paper complements the existing surveys in that the social and empirical aspects were addressed. More than 50 experts participated in a two-stage Delphi study to determine current challenges, research needs and promising standards and tools. Furthermore, an analysis of the strengths, weakness, opportunities and threats of co-simulation utilizing the analytic hierarchy process resulting in a SWOT-AHP analysis is presented. The empirical results of this study show that experts consider the FMI standard to be the most promising standard for continuous time, discrete event and hybrid co-simulation. The results of the SWOT-AHP analysis indicate that factors related to strengths and opportunities predominate

Uncertainty and Confidence in Safety Logic

Abstract Reasoning about system safety requires reasoning about confidence in safety claims. For example, DO-178B requires developers to determine the correctness of the worst-case execution time of the software. It is not possible to do this beyond any doubt. Therefore, developers and assessors must consider the limitations of execution time evidence and their effect on the confidence that can be placed in execution time figures, timing analysis results, and claims to have met timing-related software safety requirements. In this paper, we survey and assess five existing concepts that might serve as means of describing and reasoning about confidence: safety integrity levels, probability distributions of failure rates, Bayesian Belief Networks, argument integrity levels, and Baconian probability. We define use cases for confidence in safety cases, prescriptive standards, certification of component-based systems, and the reuse of safety elements both in and out of context. From these use cases, we derive requirements for a confidence framework. We assess existing techniques by discussing what is known about how well each confidence metric meets these requirements. Our results show that no existing confidence metric is ideally suited for all uses. We conclude by discussing implications for future standards and for reuse of safety elements

Methods for Weighting Decisions to Assist Modelers and Decision Analysts: A Review of Ratio Assignment and Approximate Techniques

Computational models and simulations often involve representations of decision-making processes. Numerous methods exist for representing decision-making at varied resolution levels based on the objectives of the simulation and the desired level of fidelity for validation. Decision making relies on the type of decision and the criteria that is appropriate for making the decision; therefore, decision makers can reach unique decisions that meet their own needs given the same information. Accounting for personalized weighting scales can help to reflect a more realistic state for a modeled system. To this end, this article reviews and summarizes eight multi-criteria decision analysis (MCDA) techniques that serve as options for reaching unique decisions based on personally and individually ranked criteria. These techniques are organized into a taxonomy of ratio assignment and approximate techniques, and the strengths and limitations of each are explored. We compare these techniques potential uses across the Agent-Based Modeling (ABM), System Dynamics (SD), and Discrete Event Simulation (DES) modeling paradigms to inform current researchers, students, and practitioners on the state-of-the-art and to enable new researchers to utilize methods for modeling multi-criteria decisions

On the Role of Assertions for Conceptual Modeling as Enablers of Composable Simulation Solutions

This research provides a much needed systematic review of the roles that assertions play in model composability and simulation interoperability. In doing so, this research contributes a partial solution to one of the problems of model composability and simulation interoperability—namely, why do simulation systems fail to achieve the maximum level of interoperability possible? It demonstrates the importance of the assertions that are made during model development and simulation implementation, particularly as they reflect the unique viewpoint of each developer or user. It hypothesizes that it is possible to detect composability conflicts by means of a four-step process developed by the author for capturing and comparing assertions. It demonstrates the process using a well understood example problem—the Falling Body Problem—developing a formal model of assertion, a strategy for assertion comparison, an inventory of forces, and a catalog of significant assertions that might be made for each term in the solution to the problem. Finally, it develops a software application to implement the strategy for comparing sets of assertions. The software successfully detects potential conflicts between ontologies that were otherwise determined to be ontologically consistent, thus proving the hypothesis

Reusing simulation experiments for model composition and extension

This thesis aims to reuse simulation experiments to support developing models via model reuse, with a focus on validating the resulting model. Individual models are annotated with their simulation experiments. Upon reuse of those models for building new ones, the associated simulation experiments are also reused and executed with the new model, to inspect whether the key behavior exhibited by the original models is preserved or not in the new model. Hence, the changes of model behavior resulting from the model reuse are revealed, and insights into validity of the new model are provided