DISTRIBUTED SIMULATION WITH JAVAGPSS BASED ON THE HIGH LEVEL ARCHITECTURE

This paper focuses on the High Level Architecture for reusable and interoperable distributed simulation, platform independence, and how classical simulation tools can fit into this new arena. The current integration efforts focus on GPSS/H and SLX; in this paper the GPSS/H track is described. The experiences using the standard GPSS/H version and the reasons for a Java implementation of GPSS/H, JavaGPSS, are sketched. The introduction of JavaGPSS and the incorporation of distributed simulation mechanisms based on HLA into this tool build the main issue of the remainder of this paper. New application areas are mentioned as an outlook on this new dynamic technology. 1 DISTRIBUTED SIMULATION In the past few years, the field of distributed simulation, driven by the rapid expansion and acceptance of the Internet and its multimedia front-end, the WWW, has become one of the most promising and challenging technologies in modeling and simulation. The large number of different approaches to distribute and interoperate simulations (e.g. Aggregate Level Simulation Protocol ALSP, Distributed Interactive Simulation DIS) has now lead to a unifying approach, the High Level Architecture (HLA), which has the challenging vision to support its predecessors and different time regimes. 2 HIGH LEVEL ARCHITECTURE The High Level Architecture is a simulation interoperability standard currently being developed by the US Department of Defense (DMSO 1997). The architecture is defined by : 1. rules which govern the behavior of the overall distributed simulation (Federation) and their members (Federates) (DoD 1996). 2. an interface specification, which prescribes the interface between each federate and the Runtime Infrastructure (RTI), which provides communication and coordination services to the federates. Federation communication only takes place between each federate and the RTI, not between federates themselves. The RTI as the central coordination software component as well as the federates can be located on any networked computer on an Intranet or the Internet (DoD 1997). 3. an Object Model Template (OMT) which defines the way how federations and federates have to be documented (using the Federation Object Model, FOM and the Simulation Object Model, SOM, resp.). The OMT uses a tabular approach which is well suited for automated tools and conversion into the OMT data interchange format (OMT DIF). OMTs promote the reuse of single federates or federations as a whole. Federations can be viewed as a contract between federates on how a common federation execution is intended to be run (DoD 1997a). The time management services provided by HLA allow the transparent running of federates under different time regimes (e.g. real time, time stepped, event driven) (DMSO 1997a). Even though it originates from military application surrounding, the architecture seems to be very well suited for civilian applications, too. Together with web-enabled simulation and animation components, an exciting new variety of applications and collaboration modes could be developed (Picture 1). RTI Interface Other Federates Simulation Federates Animation Federates Runtime Infrastructure (RTI) Picture 1 HLA-based Simulation and Animation