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<!-- Deleted image removed: [[Image:Aggregate Level Simulation Protocol (logo).jpg|100px|thumb|ALSP Logo]] -->
The '''Aggregate Level Simulation Protocol (ALSP)''' is a protocol and supporting software that enables simulations to interoperate with one another. Replaced by the '''[[High Level Architecture (simulation)]] (HLA)''', it was used by the US military to link analytic and training simulations.
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==History==
In 1990, the '''[[Defense Advanced Research Projects Agency]] (DARPA)''' employed '''The [[MITRE]] Corporation''' to study the application of distributed interactive simulation principles employed in '''[[SIMNET]]''' to aggregate-level constructive training simulations. Based on prototype efforts, a community-based experiment was conducted in 1991 to extend SIMNET to link the US Army's [https://archive.today/20130822204558/http://www.peostri.army.mil/PRODUCTS/CBS/home.jsp '''Corps Battle Simulation (CBS)'''] and the US Air Force's [https://web.archive.org/web/20041019105713/http://afmsrr.afams.af.mil/index.cfm?RID=SMN_AF_1000000 '''Air Warfare Simulation (AWSIM)''']. The success of the prototype and users' recognition of the value of this technology to the training community led to development of production software. The first ALSP confederation, providing air-ground interactions between CBS and AWSIM, supported three major exercises in 1992.
By 1995, ALSP had transitioned to a multi-Service program with simulations representing the US Army (CBS), the US Air Force (AWSIM), the US Navy ('''RESA'''), the US Marine Corps ([https://web.archive.org/web/20070826203844/http://www.29palms.usmc.mil/dirs/ont/mands/mwts.asp '''MTWS''']), electronic warfare ('''JECEWSI'''), logistics ('''CSSTSS'''), and intelligence ([https://web.archive.org/web/20070825010050/http://www.peostri.army.mil/
==Contributions==
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The first strategy requires few perturbations to existing simulations; interaction is facilitated entirely through the interconnection infrastructure. However, this solution does not scale well. Because of an underlying requirement for scalability, the ALSP design adopted the second strategy. ALSP prescribes that each simulation maps between the representational scheme of the confederation and its own representational scheme. This mapping represents one of the three ways in which a simulation must be altered to participate in an ALSP confederation. The remaining modifications are:
* Recognizing that the simulation
* Modifying the
In stand-alone simulations, objects come into (and go out of) existence with the passage of simulation time and the disposition of these objects is solely the purview of the simulation. When acting within a confederation, the simulation-object relationship is more complicated.
The simulation-object ownership property is dynamic, i.e. during its lifetime an object may be owned by more than one simulation. In fact, for any value of simulation time, several simulations may own different attributes of a given object. By convention, a simulation owns an object if it owns the "identifying" attribute of the object. Owning an
When a simulation creates an object, it reports this fact to the confederation to let other simulations create ghosts. Likewise, when a simulation deletes an object, it reports this fact to enable ghost deletion. Whenever a simulation takes an action between one of its objects and a ghost, the simulation must report this to the confederation. In the parlance of ALSP, this is an interaction.
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# The simulation repeats from step (1).
AIS includes a [[deadlock avoidance]] mechanism using null messages. The mechanism requires that the processes have exploitable [[Combinatorial search#Lookahead|lookahead]] characteristics.
====Object management====
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===ALSP Protocol===
The ALSP protocol is based on a set of orthogonal issues that comprise
====Simulation Protocol====
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* ''Update.'' Objects in ALSP are defined by a unique id number, a class, and a set of attributes associated with a c1ass. As a simulation changes the state its objects, it sends update messages to the ACM that provide initial or changed attribute values. The ACM then distributes the information via AIS to other simulations in that have indicated interest.
* ''Interaction.'' Interactions between objects are identified by kind. Interaction kinds are described by parameters, just as objects are described by attributes. When a
* ''Refresh request.'' A simulation can request an update of a set of attribute values for any object or class of objects by sending a refresh request message to the confederation.
* ''Delete.'' When a simulation causes one of its objects to cease to exist, the simulation sends a delete message to inform other simulations.
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Distributed object ownership presumes that no single simulation must own all objects in a confederation, but many simulations require knowledge of some objects. A simulation uses simulation protocol update messages to discover objects owned by other simulations. If this simulation is interested in the objects, it can ghost them (track their locations and state) and model interactions to them from owned objects.
Locks implement attribute ownership. A primary function of the object management protocol is to ensure that a simulation only updates attributes for which it has acquired a lock. The object manager in the ACM manages the objects and object attributes of the owned and ghosted objects known to the ACM. Services provided by the simulation/ACM protocol are used by the simulations to interact with the
Each attribute of each object known to a given ACM has a status that assumes one of three values:
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* ''Gone.'' The state of control is held elsewhere in the confederation.
From the
* ''Object Registration'' places each object-attribute pair in the locked state. The simulation may optionally specify attributes to be in the unlocked state.
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====Time Management Protocol====
The time management protocol is also a peer-level protocol that sits below the simulation protocol. It provides time management services for synchronizing simulation time among ACMs. The protocol provides services for the distributed coordination of a
The join/resign services and time synchronization mechanisms are described in Section earlier. The save mechanism provides fault tolerance. Coordination is required to produce a consistent snapshot of all ACMs, translators and simulations for a particular value of simulation time.
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The ACM uses simulation message filtering to evaluates the content of a message received from the confederation. The ACM delivers messages to its simulation that are of interest, and pass filtering criteria and discards those that are not of interest. The ACM filters two types of messages: update messages and interaction messages.
''Update messages.'' The ACM evaluates update messages based on the
''Interaction messages.'' An ACM may discard interaction messages because of the kind parameter. The kind parameter has a hierarchical structure similar to the object class structure. The simulation informs its ACM of the interaction kinds that should pass or fail the interaction filter.
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In the case of update messages, distribution of this information allows ACMs to only distribute data on classes (and attributes of classes) that are of interest to the confederation. The ABE also use this information to send only information that is of interest to the components it serves. For interaction messages, the process is similar, except that the kind parameter in the interaction message determines where the message is sent.
==
* Anita Adams, Gordon Miller, and David Seidel, November 1993, [http://ms.ie.org/alsp/biblio/93_annual_report/93_annual_report_pr.html "Aggregate Level Simulation Protocol (ALSP) 1993 Confederation Annual Report"], The MITRE Corporation. A history of the ALSP program in fiscal year 1993.
* William E. Babineau, Philip S. Barry, C. Zachary Furness, [http://ms.ie.org/alsp/biblio/SIW-Fall98/testing.rtf "Automated Testing within the Joint Training confederation (JTC)"], ''Proceedings of the Fall 1998 Simulation Interoperability Workshop'', Orlando, FL, September, 1998.
* MAJ John Bullington and Gordon Miller, September 1996, [http://ms.ie.org/alsp/biblio/MORS_TACSIM/mors_sep96.html "Intelligence Simulation Support to the Joint Training Confederation: Implications for Future Development"], TACSIM Project Office and The MITRE Corporation, published in the September 1996 edition of ''Phalanx, a MORS publication''.
* Lydia P. Dubon, 1993, [
* Laura Feinerman, Gordon Miller, David Prochnow, Richard Weatherly, Annette Wilson, and Anita Adams Zabek, [http://ms.ie.org/alsp/biblio/94_annual_report/94_an_rpt_pr.html "Aggregate Level Simulation Protocol (ALSP) Project 1994 Annual Report"], dated March 1995, The MITRE Corporation. A history of the ALSP program in fiscal year 1994.
* Mary C. Fischer, April 1994, [https://web.archive.org/web/20071013080320/http://ms.ie.org/alsp/biblio/elecsim_94_paper_fischer/elecsim_connie.html "Aggregate Level Simulation Protocol (ALSP) - Managing Confederation Development"], U. S. Army Simulation, Training and Instrumentation Command. A paper presented on the ''1994 Elecsim Internet Conference''.
* Mary C. Fischer, Anita Adams, Gordon Miller, June 1994, [http://ms.ie.org/alsp/biblio/mors_94_fischer/mors_94_fischer.html "Aggregate Level Simulation Protocol (ALSP) - Training for the Future"], U. S. Army Simulation, Training and Instrumentation Command and The MITRE Corporation. A paper presented at the ''Military Operations Research Symposium 62'' meeting at the Air Force Academy in Colorado Springs, Colorado.
* Mary C. Fischer, December 1994, [
* Mary C. Fischer, April 1995, [http://ms.ie.org/alsp/biblio/itec_95_fischer/itec_95_fischer.html "Aggregate Level Simulation Protocol (ALSP) - Future Training with Distributed Interactive Simulations"], U. S. Army Simulation, Training and Instrumentation Command. A paper presented at the ''1995 International Training Equipment Conference'' on 25–27 April 1995 at The Hague in The Netherlands.
* Mary C. Fischer, September 1995, [http://ms.ie.org/alsp/biblio/DRG_Paper/36nato-w.html "Joint Simulated Battlefield"], U. S. Army Simulation, Training, and Instrumentation Command, published in ''Proceedings of the 36th Defence Research Group (DRG) Seminar on Modeling and Simulation'', 5–8 September 1995, Washington, D.C.
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* George J. McFadden, [http://ms.ie.org/alsp/biblio/SIW_Spring00/00S-SIW-032.doc "An Approach to Management of Enumerated Data in Federations"], ''Proceedings of the Spring 2000 Simulation Interoperability Workshop'', Orlando, FL, March, 2000.
* Gordon Miller and Anita Zabek, March 1996, [http://ms.ie.org/alsp/biblio/mors_96_miller/mors_96.html "The Joint Training Confederation and the Aggregate Level Simulation Protocol"], The MITRE Corporation, published in the June 1996 edition of ''Phalanx, a MORS publication''.
* {{cite journal | author1 = Ernest Page | author2 = Brad Canova | author3 = John Tufarolo | title = A Case Study of Verification, Validation and Accreditation for Advanced Distributed Simulation |
* {{cite conference | author1 = David L. Prochnow | author2 = Ernest H. Page | author3 = Mary C. Fischer | title = Management of the Joint Training Confederation Family of Specifications |
* David L. Prochnow, Mary C. Fischer, [https://web.archive.org/web/20081222093252/http://www.sisostds.org/index.php?tg=fileman
* {{cite conference | author1 = David L. Prochnow | author2 = Ernest H. Page | author3 = Bryan Youmans | title = Development of a Federation Management Tool: Implications for HLA |
* David Seidel, March 1993, [http://ms.ie.org/alsp/biblio/89-92_history/89-92_history.html "Aggregate Level Simulation Protocol (ALSP) Program Status and History"], The MITRE Corporation. A history of the ALSP program from its beginning in 1989 through 1992.
* John Tufarolo and Ernest Page, [http://portal.acm.org/ft_gateway.cfm?id=256869&type=pdf&coll=portal&dl=ACM&CFID=3273248&CFTOKEN=54531066 "Evolving the VV&A Process for the ALSP Joint Training Confederation"], ''Proceedings for the 1996 Winter Simulation Conference'', pp. 952–958, Coronado, CA, 8–11 December 1996.
* Richard Weatherly, David Seidel, and Jon Weissman, July 1991, [http://ms.ie.org/alsp/biblio/ssc_91_paper/SSC_91_Paper.html "Aggregate Level Simulation Protocol"], The MITRE Corporation. A paper presented at the ''1991 Summer Computer Simulation Conference'' in Baltimore, Maryland
* Richard Weatherly, Annette Wilson, and Sean Griffin, December 1993, [
* {{Cite
* Annette Wilson and Richard Weatherly, April 1994, [https://web.archive.org/web/20071013081152/http://ms.ie.org/alsp/biblio/elecsim_94_paper/Elecsim_94_mod.html "New Traffic Reduction and Management Tools for ALSP Confederations"], The MITRE Corporation. A paper presented on the ''1994 Elecsim Internet Conference''.
* Annette Wilson and Richard Weatherly, December 1994, [
==References==
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