For decades, building simulations of complex systems—whether in engineering, defense, or science—has been limited by incompatible software tools and inconsistent methods. A new study proposes a practical solution rooted in mathematically grounded systems theory. Researchers Professor Bernard Zeigler from RTSync Corp., Dr. Robert Kewley from simlytics.cloud, and Professor Gabriel Wainer from Carleton University have shown that a modeling approach called DEVS, short for Discrete Event System Specification, can serve as a common standard for simulating a wide variety of systems, no matter how different they may seem.
Professor Zeigler and his team focused on three key features of DEVS: closure under coupling, universality, and uniqueness. These features may sound technical, but they offer real-world benefits. Closure under coupling means that smaller models can be combined into larger ones while still remaining within the DEVS framework, like stacking Lego blocks to build a bigger restackable structure. “Any system constructed by wiring up multiple DEVS models can be mathematically represented as a single DEVS model that gives the same results when simulated.” Professor Zeigler explained. This means that even very complex systems can be treated in the same way as simple ones, making simulations easier to manage and scale up.
Professor Zeigler’s team also highlighted DEVS universality, which is its ability to describe any system that works through events happening at specific times, known as discrete events. For example, whether it’s a train schedule, a manufacturing line, or an online transaction system, DEVS can model it. “DEVS representation is also unique, meaning the fundamental, simplest version of any such system has an exact match within the DEVS models,” said Professor. Wainer. This allows DEVS to pull diverse models together under one consistent standard.
Their research provides practical steps for adapting older or non-standard systems to work with DEVS. By “wrapping” these systems—adding a compatible interface so they can communicate like DEVS models—they can work alongside other DEVS components. This approach is especially helpful for organizations like the U.S. Department of Defense, which often uses older simulation tools. As Dr. Kewley pointed out, “This removes a major barrier to widespread adoption of DEVS within organizations with large legacy simulation investments”.
This approach supports the Department of Defense’s Modular Open Systems Approach, or MOSA, a design strategy that emphasizes building systems from separate, interchangeable parts that are easy to update and combine. The researchers suggest that DEVS can be the foundation for this approach by making sure that all components of a system, no matter how they were created, can work together smoothly. A concept called the DEVS Bus helps achieve this by allowing different tools and systems to talk to each other in a shared simulation environment.
Professor Zeigler’s study also looked at two useful techniques: flattening and deepening. Flattening means simplifying complex models by removing nested layers, so all parts are on the same level, which helps simulations run faster. Deepening is the opposite—it introduces more structure by organizing parts into larger reusable modules, making them easier to manage and build upon. “Flattening eliminates structure by reducing message traffic and increasing simulation efficiency; deepening can introduce hierarchical structure to enhance modularity, reuse, and scalability,” Professor Zeigler said.
Professor Zeigler and his team finish by outlining how DEVS could evolve. They propose creating standard DEVS modules, improving simulation tools, and making sure DEVS works well with widely-used platforms like FMI, which stands for Functional Mock-up Interface, a standard for model exchange and co-simulation. All these efforts aim to build a flexible and reliable DEVS-based system where models can be reused, adapted, and combined with ease.
By grounding their approach in well-established theory and providing easy-to-use methods for connecting different systems, the researchers believe DEVS offers a practical way forward. As software becomes more interconnected and complex, having a reliable way to simulate and test it holistically is more important than ever—and this study offers a strong, mathematically-backed solution.
Dr. Doowhan Kim, president of RTSync, emphasized that DEVS has consistently proven itself to provide the rigor and modularity that industry demands for scalable, trustworthy simulation environments. He said, “RTSync is leading the effort to commercialize DEVS-based platforms such as real-world digital twins and cloud-based simulation infrastructures.” At the same time, organizations such as the International Standards Organization (ISO) are working to standardize DEVS, ensuring interoperability and credibility across defence, science, and industrial sectors. Together, these efforts mark DEVS’s transition from academic research to a globally recognized backbone for scientific investigation and engineering innovation.
Journal Reference
Zeigler B., Kewley R., Wainer G., “DEVS Closure Under Coupling, Universality, and Uniqueness: Enabling Simulation and Software Interoperability from a System-Theoretic Foundation.” Computers, 2025. DOI: https://doi.org/10.20944/preprints202510.1207.v1
About the Authors
Bernard P. Zeigler is Professor Emeritus of Electrical and Computer Engineering at the University of Arizona, where he taught until his retirement. Alongside that role, he serves as Chief Scientist for a spin-off company originally launched from his laboratory at the Arizona Center for Integrative Modeling and Simulation (ACIMS). He earned his B.S. in Engineering Physics from McGill University, an M.S. in Electrical Engineering from MIT, and a Ph.D. in Computer/Communication Sciences from the University of Michigan. He is best known for developing the DEVS structure for modeling and simulation, and he holds fellow status in major professional societies. His work spans academic research and commercial applications of modeling in systems engineering and software environments.
Robert Kewley is Director and Systems Engineer at Simlytics.cloud LLC, where he focuses on applying simulation and modeling methods to complex systems, including operational, cloud-based, and “system of systems” environments. His career includes roles in defense systems engineering and simulation education. He has authored work in data-driven modeling, federated simulations, and distributed model frameworks. At Simlytics, he leads efforts to integrate older and newer technologies so they can be used together in flexible simulation platforms. Kewley’s background blends technical depth in systems engineering with a practical orientation toward industrial and organizational challenges.
Gabriel Wainer is a Professor in the Department of Systems and Computer Engineering at Carleton University in Ottawa, Canada, and directs the Advanced Real-Time Simulation Lab. He holds a Ph.D. from the University of Buenos Aires/Aix-Marseille University, and has held visiting positions at research institutions in Argentina, France and Canada. His research spans modeling and simulation methods, real-time systems, cellular models, and parallel or web-based simulation environments. He has published extensively, led major grants, and served in editorial and conference leadership roles. Wainer continues to shape how simulation tools are developed, integrated and taught.
