The Question

Simulation modeling methodology deals with creation and manipulation of models over the lifetime of their use. Motivated by the recognition that the manner in which a simulation model is conceived, developed and used can have a significant impact on the ability of the model to achieve its objectives, modeling methodology has been an active research area since the inception of digital computer simulation.

Over the past forty years the practice of simulation model creation has evolved from coding in general-purpose languages, to model development in special-purpose simulation languages, to model design using higher-level simulation model specification languages and formalisms, to comprehensive theories of simulation modeling and holistic environment support for the modeling task. Thematic in much of the modeling methodological work to date has been the recognition of Dijkstra's principle of the "separation of concerns" which argues for the separateness of specification and implementation (Dijkstra 1972). In many cases, this philosophy has been tempered by the pragmatic observations of Swartout and Balzer (1982), who observe that separation is a worthy goal but not achievable in totality since any specification, S, may be viewed as an implementation of some higher-order specification, S'.

Another argument in favor of the intertwining of specification and implementation is that technological advancements may enable new approaches to accomplishing a task - approaches that were not even conceivable prior to the advent of the technology. Consider, for example, the advent of the assembly line in manufacturing. The potential of the WWW assuch a technology push is cited in a recent article that describes the application of the WWW within the manufacturing process (Erkes et al. 1996), ``Our initial experiments at putting engineering, design and manufacturing services on the Web are so successful that we believe we should rethink the traditional approaches and tools for coordinating large, distributed teams.'' With respect to simulation, a similar revolution seems plausible. Web technology has the potential to significantly alter the ways in which simulation models are developed (collaboratively, by composition), documented (dynamically, using multimedia), analyzed (open, widespread investigation) and executed (using massive distribution).

Is the web such an elixir, demanding that we radically alter our modeling philosophies and approaches? Or is web-based execution merely another implementation detail that can, and should, be abstracted from the model development process?


  1. Dijkstra, E.W. 1976. A Discipline of Programming. Prentice-Hall, Englewood Cliffs, NJ.
  2. Erkes, J.W.; Kenny, K.B.; Lewis, J.W.; Sarachan, B.D.; Sobolewski, M.W; and R.N. Sum, Jr. 1996. ``Implementing Shared Manufacturing Services on the World-Wide Web.'' Communications of the ACM, 39, no. 2 (Feb.):34-45.
  3. Swartout W.; and R. Balzer. 1982. ``On the Inevitable Intertwining of Specification and Implementation.'' Communications of the ACM, 25, no. 7(July):438-440.


Ernest H. Page is a Lead Scientist in modeling and simulation at The MITRE Corporation where he is currently working on the Aggregate Level Simulation Protocol (ALSP) program and is the Principal Investigator for a MITRE Sponsored Research project on web-based simulation. He received the Ph.D., M.S. and B.S. degrees in Computer Science from Virginia Tech in 1994, 1990 and 1988 respectively. He is active within the U.S. DoD modeling and simulation community, serving on the Defense Modeling and Simulation Office (DMSO) Verification, Validation and Accreditation Technology Working Group (1996-) and on the Testing (1995, 1996), Interface Specification (1995) and Time Management (1996) Working Groups within the DMSO High Level Architecture (HLA) initiative. He has also served on the Planning and Review Panel for the Simulation Interoperability Workshops (1997). Dr. Page has served as the Secretary/Treasurer (1995-1997) for the Association for Computing Machinery (ACM) Special Interest Group on Simulation (SIGSIM) and currently holds the position of Vice Chair. He is on the Program Committees for the 1998 SCS International Conference on Web-Based Modeling and Simulation and the 1998 SPIE AeroSense Symposium Technical Conference on Web-Based Simulation. His research interests include discrete event simulation, parallel and distributed systems, and software engineering. He is a member of ACM, SIGSIM, IEEE CS and Upsilon Pi Epsilon. (Address: The MITRE Corporation, 1820 Dolley Madison Boulevard, McLean, VA, 22102-3481, E-mail:

Web-Based Simulation Modeling

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