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