DEVS and HLA: Complementary paradigms for modeling and simulation?

The HLA represents a major advance in M&S methodology as a standard mandate d by the U.S. Department of Defense (DoD) to promote simulation interoperab ility and reuse. However; as currently formulated for acceptance as an IEEE standard it standardizes certain aspects of the M&S process while leaving others unspecified. On the other hand the Discrete Event System Specificati on (DEVS) methodology has been under development since the '70s and formali zes certain aspects of the M&S process while not addressing others. In this paper, we critically examine the current state of both the HLA and DEVS sp ecifications. We point out the strengths and limits/omissions of each. We p ose the question to each: Are the limits and omissions appropriate at this stage of development or do they represent more fundamental limitations that constitute a barrier to future development? Particularly: since it has the power of mandate, any fundamental limitations on HLA might lead to defacto non-acceptance of the standard with negative consequences on the course of M&S methodology We argue that the limits of each are indeed critical limit ations bur that a combination of HLA and DEVS can better overcorne these ba rriers to widespread adoption than can either alone. Finally, we suggest a roadmap for such a combination and point out the possibilities for employin g it in such expanding initiatives as Simulation-Based Acquisition.