The High Level Architecture (HLA) was developed to provide a common architecture for distributed modeling and simulation. Initial HLA development began within the US Department of Defense (DoD) in the mid-1990s. International standardization was achieved in 2000, when the HLA was established as a set of Institute of Electrical and Electronics Engineers (IEEE) standards. Today, the HLA is used worldwide to link constructive and virtual simulations as well as interfaces to live components. HLA federations support a wide variety of applications including training, testing, and acquisition analysis.

Subsequent to the 2000 IEEE standardization of the core HLA standard [the HLA Framework and Rules, the HLA Interface Specification, and the HLA Object Model Template (OMT)] many improvements have been proposed. Several of the proposals incorporate emerging technologies. Among the proposed changes are HLA applications programming interfaces which allow dynamic linking (allowing federations to change run-time infrastructures easily), a web enabled HLA interface, fault tolerance services, and additional flexibility in update rates. Proposed changes to the OMT include additional metadata to characterize HLA federates and federations; additional information about the computing hardware, network, and HLA services used by federates; and an update of the data interchange format to take advantage of advances in the Extensible Markup Language (XML). As part of the periodic review of IEEE standards, the HLA standards have been opened for revision with balloting anticipated in 2006.

This paper will provide a brief background on the HLA and then discuss the process used to update the IEEE versions of the HLA specifications. Each of the major improvements that have been made in that process is described. Finally, information is provided on how readers can participate in the evolution of the HLA standards.