| HLA is a framework to integrate distributed | | | | Federation Management, Data Management, |
| software entities running in heterogeneous | | | | Object Management, Ownership Management, |
| environment (both hardware and software wise) | | | | Distributed Data Management and Time |
| and communicating with each other over a | | | | Management. Federates together with RTI |
| network to achieve the overall goal ; | | | | constitute a FEDERATION. The RTI allows |
| following certain specifications while doing | | | | creation/destruction of federation, join |
| so.The High Level Architecture (HLA) is a | | | | resign of federates and data exchanges among |
| software architecture for creating computer | | | | federates. It optionally provides filtered |
| simulations out of component simulations. It | | | | data delivery and may handle errors in order |
| was proposed by US DoD and later standardized | | | | of receiving data due to network delays and |
| by IEEE as an open standard IEEE 1516.The | | | | other speed mismatches. These functionalities |
| main aim of HLA is re-usability and | | | | are according to 10 rules (5 rules for |
| interoperability of complex distributed | | | | federation & 5 for federates) of HLA |
| software entities. So, an HLA-compliant Air | | | | standard.Although HLA was developed for |
| Traffic Controller simulation can be used by | | | | military simulations but it is a general |
| many other HLA-compliant applications, no | | | | purpose architecture and can be used building |
| matter in which computing environment they | | | | simple to complex applications. Some of the |
| are developed and running.This architecture | | | | simple applications are chat and multi-user |
| is just a specification and not an | | | | games like Tic-Tac-Toe. Complex applications |
| implementation. It is essentially a | | | | may include distributed war-gaming |
| service-oriented architecture. Any | | | | applications with intense data exchanges |
| HLA-compliant simulation is called a | | | | among participating entities.With this brief |
| FEDERATE. A federate can provide some service | | | | introduction, its time to develop |
| (data) to other federates or it may receive | | | | HLA-compliant applications. You can start |
| required data from other federates. This data | | | | simply by downloading RTI software. It comes |
| exchange intent is maintained in a repository | | | | with sample federates and their source code |
| called FEDERATION OBJECT MODEL (FOM) | | | | to start with. Suggested websites and books |
| implemented in accordance with OBJECT MODEL | | | | are mentioned below.* Suggested Website for |
| TEMPLATE (OMT).A federate may be a PRODUCER | | | | HLA specification |
| or a CONSUMER or both. A producer publishes | | | | |
| its services and consumer subscribes to these | | | | US Defense Modeling and Simulation Office |
| services. The repository acts a service | | | | official website |
| directory and uses standard data exchange | | | | |
| format XML. To communicate with each other, | | | | ( Suggested Book |
| federates need a supporting communication | | | | |
| software called RUN-TIME INFRASTRUCTURE (RTI) | | | | Frederick Kuhl, Richard Weatherly, Judith |
| which is an implementation of six groups of | | | | Dahmann, Creating Computer Simulation Systems |
| services as specified in HLA framework and | | | | - An Introduction to the High Level |
| caters to the requirements of distributed | | | | Architecture., PHI, 2002. |
| simulations. These six groups of services are | | | | |