Editing High Level Architecture (section)

{{Short description|Standard for distributed simulation}}
{{About|the IEEE standard for distributed simulation|3=High- and low-level}}
{{Use American English|date = March 2019}}
The '''High Level Architecture''' ('''HLA''') is a standard for distributed simulation, used when building a simulation for a larger purpose by combining (federating) several simulations.<ref name="Kuhl">{{cite book |last1=Kuhl |first1=Frederick |last2=Weatherly |first2=Richard |last3=Dahmann |first3=Judith |title=Creating Computer Simulation Systems: An Introduction to the High Level Architecture |date=October 18, 1999 |publisher=Prentice Hall |isbn=0130225118 |edition=1}}</ref> The standard was developed in the 1990s under the leadership of the [[US Department of Defense]]<ref name="Dahmann1997">{{cite book |last1=Dahmann |first1=Judith |title=Proceedings of the 29th conference on Winter simulation - WSC '97 |chapter=The Department of Defense High Level Architecture |pages=142–149 |chapter-url=https://www.informs-sim.org/wsc97papers/0142.PDF |doi=10.1145/268437.268465|year=1997 |isbn=078034278X |s2cid=6047580 }}</ref> and was later transitioned to become an open international IEEE standard. It is a recommended standard within [[NATO]] through [[STANAG]] 4603.<ref>{{cite book |title=STANAG 4603: Modelling and Simulation Architecture Standards for Technical Interoperability: High Level Architecture (HLA) |publisher=NATO}}</ref> Today the HLA is used in a number of domains including defense and security and civilian applications.

The purpose of HLA is to enable interoperability and reuse. Key properties of HLA are:
* The ability to connect simulations running on different computers, locally or widely distributed, independent of their operating system and implementation language, into one Federation.
* Ability to specify and use information exchange data models, Federation Object Models (FOMs), for different application domains.
* Services for exchanging information using a publish-subscribe mechanism, based on the FOM, and with additional filtering options.
* Services for coordinating logical (simulation) time and time-stamped data exchange.
* Management services for inspecting and adjusting the state of a Federation.

HLA forms the basis for developing standardized and extendable FOMs in different communities, for example in aerospace and defense.

The architecture specifies the following components.

[[File:HLA_Federation.png|thumb|right|Components of an HLA federation]]

* A '''Run-time Infrastructure''' (RTI) that provides a standardized set of services through different programming languages. These services include information exchange, synchronization and federation management
* '''Federates''' that are individual simulation systems using RTI services.
* A '''Federation Object Model''' (FOM) that specifies the Object Classes and Interaction Classes used to exchange data. The FOM can describe information for any domain.

Together the above components form a '''Federation'''.

The HLA standard consists of three parts:

#  '''IEEE Std 1516-2010 Framework and Rules''',<ref name="RULES">{{cite book |title=IEEE Standard for Modeling and Simulation (M&S) High Level Architecture (HLA)— Framework and Rules |date=18 August 2010 |publisher=IEEE Computer Society |isbn=978-0-7381-6251-5 |url=https://standards.ieee.org/ieee/1516/3744/}}</ref> which specifies ten architectural rules that the components or the entire federation shall adhere to.
#  '''IEEE Std 1516.1-2010 Federate Interface Specification''',<ref name="IFSPEC">{{cite book |title=IEEE Standard for Modeling and Simulation (M&S) High Level Architecture (HLA)— Federate Interface Specification |date=18 August 2010 |publisher=IEEE Computer Society |isbn=978-0-7381-6247-8 |url=https://standards.ieee.org/ieee/1516.1/3745/}}</ref> which specifies the services that shall be provided by the RTI. The services are provided as C++ and Java APIs as well as Web Services.
# '''IEEE Std 1516.2-2010 Object Model Template Specification''',<ref name="OMTSPEC">{{cite book |title=IEEE Standard for Modeling and Simulation (M&S) High Level Architecture (HLA)— Object Model Template (OMT) Specification |date=18 August 2010 |publisher=IEEE Computer Society |isbn=978-0-7381-6249-2 |url=https://standards.ieee.org/ieee/1516.2/3746/|archive-url=https://web.archive.org/web/20190818170807/https://standards.ieee.org/content/ieee-standards/en/standard/1516_2-2010.html|url-status=live|archive-date=August 18, 2019}}</ref> which specifies the format that HLA object models, such as the FOM, shall use.