yaRTI, a Ada 95 HLA run-time infrastructure

HLA stands for High Level Architecture. It is a standard developed by the US Department of Defense to achieve the interoperation and the reuse of simulations. The formal definition of the HLA comprises three main parts: the HLA rules, the HLA interface specification (I/F Spec) and the HLA Object Model Template (OMT). A HLA Run-Time Infrastructure is a middleware that implements the I/F Spec, allowing a set of simulations (a federation) to interoperate. The standardization process for the HLA is in progress (IEEE P1516). For the time now, the DoD has sponsored the development of RTI prototypes, and commercial products begin to appear. All are developed in C or C++. yaRTI is the first pure Ada 95 implementation of the HLA I/F Spec, taking advantage of the powerful distribution and tasking features of the language. The paper mainly focuses on a general description of the HLA, a more precise description of the I/F Spec, the presentation of the architecture of yaRTI and the major implementation characteristics, the main issues encountered and the lessons learned.