Live, virtual, and constructive
Encyclopedia
Live, Virtual, and Constructive (LVC) Simulation
is a broadly used taxonomy
for classifying Models and Simulation
(M&S). However, categorizing
a simulation
as a live, virtual, or constructive environment is problematic since there is no clear division between these categories. The degree of human participation in a simulation is infinitely variable, as is the degree of equipment realism. The categorization of simulations also lacks a category for simulated people working real equipment. The LVC categories are defined as follows:
Other associated terms are as follows:
LVC-IA bridges M&S technology to the people who need and use the information
gained through simulation
. To accomplish this a LVC-IA provides the following:
For over a decade, the ultimate goal of the DoD in M&S is to create a LVC-IA to assembly models and simulations quickly, which create an operationally valid LVC environment to train, develop doctrine and tactics, formulate operational plans and assess warfighting situations. A common use of these LVC environments will promote closer interaction between operations and acquisition communities. These M&S environments will be constructed from composeable
components interoperating through an integrated architecture. A robust M&S capability enables the DOD to meet operational and support objectives effectively across the diverse activities of the military services, combatant commands and agencies.
The number of available architectures have increased over time. M&S trends indicate that once a community of use develops around an architecture, that architecture is likely to be used regardless of new architectural developments. M&S trends also indicate that few, if any, architectures will be retired as new ones come online. When a new architecture is created to replace one or more of the existing set, the likely outcome is one more architecture will be added to the available set. As the number of mixed-architecture events increase over time, the inter-architecture communication problem increases as well.
M&S has made significant progress in enabling users to link critical resources through distributed architectures.
In the mid 1980s, SIMNET
became the first successful implementation of a large-scale, real-time, man-in-the-loop simulator networking for team training and mission rehearsal in military operations. The earliest successes that came through the SIMNET program was the demonstration that geographically dispersed simulation systems could support distributed training by interacting with each other across network connections.
The Aggregate Level Simulation Protocol
(ALSP) extended the benefits of distributed simulation to the force-level training community so that different aggregate-level simulations could cooperate to provide theater-level experiences for battle-staff training. The ALSP has supported an evolving “confederation of models” since 1992, consisting of a collection of infrastructure software and protocols for both inter-model communication through a common interface and time advance using a conservative Chandy-Misra based algorithm.
At about the same time, the SIMNET protocol evolved and matured into the Distributed Interactive Simulation
(DIS) Standard. DIS allowed an increased number of simulation types to interact in distributed events, but was primarily focused on the platform-level training community. DIS provided an open network protocol standard for linking real-time platform-level wargaming simulations.
In the mid 1990s, the Defense Modeling and Simulation Office
(DMSO) sponsored the High Level Architecture
(HLA) initiative. Designed to support and supplant both DIS and ALSP, investigation efforts were started to prototype an infrastructure capable of supporting these two disparate applications. The intent was to combine the best features of DIS and ALSP into a single architecture that could also support uses in the analysis and acquisition communities while continuing to support training applications.
The DoD test community started development of alternate architectures based on their perception that HLA yielded unacceptable performance and included reliability limitations. The real-time test range community started development of the Test and Training Enabling Architecture (TENA) to provide low-latency, high-performance service in the hard-real-time application of integrating live assets in the test-range setting. TENA, through its common infrastructure, including the TENA Middleware and other complementary architecture components, such as the TENA Repository, Logical Range Archive, and other TENA utilities and tools, provides the architecture and software implementation and capabilities necessary to quickly and economically enable interoperability
among range systems, facilities, and simulations.
Similarly, the U.S. Army started the development of the Common Training Instrumentation Architecture (CTIA) to link a large number of live assets requiring a relatively narrowly bounded set of data for purposes of providing After Action Reviews (AARs) on Army training ranges in the support of large-scale exercises.
Other efforts that make the LVC architecture space more complex include universal interoperability software packages such as OSAMS or CONDOR developed and distributed by commercial vendors.
As of 2010 all of the DoD architectures remain in service with the exception of SIMNET. Of the remaining architectures: CTIA, DIS, HLA, ALSP and TENA, some are in early and growing use (e.g., CTIA, TENA) while others have seen a user-base reduction (e.g., ALSP). Each of the architectures is providing an acceptable level of capability within the areas where they have been adopted. However, DIS, HLA, TENA, and CTIA-based federations are not inherently interoperable with each other. when simulations rely on different architectures, additional steps must be taken to ensure effective communication between all applications. These additional steps, typically involving interposing gateways or bridges between the various architectures, may introduce increased risk, complexity, cost, level of effort, and preparation time. Additional problems extend beyond the implementation of individual simulation events. As a single example, the ability to reuse supporting models, personnel (expertise), and applications across the different protocols is limited. The limited inherent interoperability between the different protocols introduces a significant and unnecessary barrier to the integration of live, virtual, and constructive simulations.
, a technical system that interacts directly with people. The following table identifies the 1996 challenges associated with the technical, cultural and managerial aspects. In addition, the challenges or gaps found in a 2009 study are also included. The table shows there is little difference between the challenges of 1996 and the challenges of 2009.
(JCID) lifecycle. See the "M&S in the JCID Process" figure. A LVC-IA is also considered an Ultra Large Scale (ULS) system due to the use by a wide variety of stakeholders with conflicting needs and the continuously evolving construction from heterogeneous parts. By definition, people are not just users but elements of a LVC simulation.
During the development of various LVC-IA environments, attempts to understand the foundational elements of integration, composability and interoperability emerged. As of 2010, our understanding of these three elements are still evolving, just as software development continues to evolve. Consider software architecture; as a concept it was first identified in the research work of Edsger Dijkstra in 1968 and David Parnas in the early 1970s. The area of software architecture was only recently adopted in 2007 by ISO as ISO/IEC 42010:2007. Integration is routinely described using the methods of architectural and software patterns. The functional elements of integration can be understood due to universality of integration patterns, e.g. Mediation
(intra-communication) and Federation
(inter-communication); process, data synchronization
and concurrency pattern
s.
A LVC-IA is dependent on the Interoperability and Composability attributes, not just the technical aspects, but the social or cultural aspects as well. There are sociotechnical challenges, as well as ULS system challenges associated with these features. An example of a cultural aspect is the problem of composition validity. In an ULS the ability to control all interfaces to ensure a valid composition is extremely difficult. The VV&A paradigms are challenged to identfy a level of acceptable validity.
(LCIM) which identified seven levels of interoperability among participating systems as a method to describe technical interoperability and the complexity of interoperations. Zeigler's Architecture for M&S extends on the three basic levels of interoperability; pragmatic, semantic, and syntactic. The pragmatic level focuses on the receiver’s interpretation of messages in the context of application relative to the sender’s intent. The semantic level concerns definitions and attributes of terms and how they are combined to provide shared meaning to messages. The syntactic level focuses on a structure of messages and adherence to the rules governing that structure. The linguistic interoperability concept supports simultaneous testing environment at multiple levels. The LCIM associate the lower layers with the problems of simulation interoperation while the upper layers relate to the problems of reuse and composition of models. They conclude “simulation systems are based on models and their assumptions and constraints. If two simulation systems are combined, these assumptions and constraints must be aligned accordingly to ensure meaningful results”. This suggests that levels of interoperability that have been identified in the area of M&S can serve as guidelines to discussion of information exchange in general. The Zeigler Architecture provides an architecture description language
or conceptual model in which to discuss M&S. The LCIM provides a conceptual model as a means to discuss integration, interoperability and composability. The three linguistic elements relates the LCIM to the Ziegler conceptual model. Architectural and structural complexity an area of research in systems theory to measure the cohesion
and coupling
and is based on the metrics commonly used in software development projects. Zeigler, Kim, and Praehofer presents a theory of modeling and simulation which provides a conceptual framework and an associated computational approach to methodological problems in M&S. The framework provides a set of entities and relations among the entities that, in effect, present a ontology of the M&S domain.
In Improving the Composability of Department of Defense Models and Simulation, the factors associated with the ability to provide composability are as follows:
The development & use costs associated with LVC can be summarized as follows:
In contrast, the fidelity
of M&S is highest in Live, lower in Virtual, and lowest in Constructive. As such, DoD
policy is a mixed use of LVC through the Military Acquisition
life cycle, also known as the LVC Continuum. In the LVC Continuum figure to the right, the JCIDS process is related to the relative use of LVC through the Military Acquisition
life cycle.
Simulation
Simulation is the imitation of some real thing available, state of affairs, or process. The act of simulating something generally entails representing certain key characteristics or behaviours of a selected physical or abstract system....
is a broadly used taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
for classifying Models and Simulation
Modeling and simulation
Modeling and simulation is the use of models, including emulators, prototypes, simulators, and stimulators, either statically or over time, to develop data as a basis for making managerial or technical decisions. The terms "modeling" and "simulation" are often used interchangeably.The use of...
(M&S). However, categorizing
Categorization
Categorization is the process in which ideas and objects are recognized, differentiated and understood. Categorization implies that objects are grouped into categories, usually for some specific purpose. Ideally, a category illuminates a relationship between the subjects and objects of knowledge...
a simulation
Simulation
Simulation is the imitation of some real thing available, state of affairs, or process. The act of simulating something generally entails representing certain key characteristics or behaviours of a selected physical or abstract system....
as a live, virtual, or constructive environment is problematic since there is no clear division between these categories. The degree of human participation in a simulation is infinitely variable, as is the degree of equipment realism. The categorization of simulations also lacks a category for simulated people working real equipment. The LVC categories are defined as follows:
- Live - M&S involving real people operating real systems, e.g. a pilot flying a jet.
- Virtual - M&S involving real people operating simulated systems. Virtual simulations inject a Human-in-the-LoopHuman-in-the-LoopHuman-in-the-Loop is defined as a model that requires human interaction. HITL is associated with Virtual Modeling & Simulation in the Live, Virtual, and Constructive taxonomy. HITL models may conform to Human factors requirements as is the case of a Mockup...
into a central role by exercising motor controlMotor controlMotor control are information processing related activities carried out by the central nervous system that organize the musculoskeletal system to create coordinated movements and skilled actions...
skills (e.g., flying a simulated jet), decision makingDecision makingDecision making can be regarded as the mental processes resulting in the selection of a course of action among several alternative scenarios. Every decision making process produces a final choice. The output can be an action or an opinion of choice.- Overview :Human performance in decision terms...
skills (e.g., committing fire control resources to action), or communication skills (e.g., as members of a C4I team).
- Constructive - M&S involving simulated people operating simulated systems. Real people stimulate (provide inputs) to such simulations, but are not involved in determining the outcomes. See Cognitive modelCognitive modelA cognitive model is an approximation to animal cognitive processes for the purposes of comprehension and prediction. Cognitive models can be developed within or without a cognitive architecture, though the two are not always easily distinguishable.In contrast to cognitive architectures, cognitive...
.
Other associated terms are as follows:
- LVC EnterpriseEnterprise application integrationEnterprise Application Integration is defined as the use of software and computer systems architectural principles to integrate a set of enterprise computer applications.- Overview :...
- The overall enterprise of resources in which LVC activities take place. - LVC IntegrationEnterprise application integrationEnterprise Application Integration is defined as the use of software and computer systems architectural principles to integrate a set of enterprise computer applications.- Overview :...
- The process of linking LVC simulations through a suitable technology or protocol to exploit simulation interoperabilityInteroperabilityInteroperability is a property referring to the ability of diverse systems and organizations to work together . The term is often used in a technical systems engineering sense, or alternatively in a broad sense, taking into account social, political, and organizational factors that impact system to...
within a federated simulation environment such as the high level architecture (simulation) or Eurosim. - LVC Integrating ArchitectureEnterprise application integrationEnterprise Application Integration is defined as the use of software and computer systems architectural principles to integrate a set of enterprise computer applications.- Overview :...
(LVC-IA) - The aggregate representation of the foundational elements of a LVC Enterprise, including hardwareHardware-in-the-loop simulationHardware-in-the-loop simulation is a technique that is used in the development and test of complex real-time embedded systems. HIL simulation provides an effective platform by adding the complexity of the plant under control to the test platform...
, softwareComputer softwareComputer software, or just software, is a collection of computer programs and related data that provide the instructions for telling a computer what to do and how to do it....
, networksComputer networkA computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....
, databaseDatabaseA database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...
s and interfaces, policiesSeparation of mechanism and policyThe separation of mechanism and policy is a design principle in computer science. It states that mechanisms should not dictate the policies according to which decisions are made about which operations to authorize, and which resources to...
, agreements, certifications/accreditations and business rules. LVC-IA is intrinsically an Enterprise ArchitectureEnterprise architectureAn enterprise architecture is a rigorous description of the structure of an enterprise, which comprises enterprise components , the externally visible properties of those components, and the relationships between them...
, given the system-of-systemsSystem of systemsSystem of systems is a collection of task-oriented or dedicated systems that pool their resources and capabilities together to create a new, more complex system which offers more functionality and performance than simply the sum of the constituent systems...
environment it must support.
LVC-IA bridges M&S technology to the people who need and use the information
Information
Information in its most restricted technical sense is a message or collection of messages that consists of an ordered sequence of symbols, or it is the meaning that can be interpreted from such a message or collection of messages. Information can be recorded or transmitted. It can be recorded as...
gained through simulation
Simulation
Simulation is the imitation of some real thing available, state of affairs, or process. The act of simulating something generally entails representing certain key characteristics or behaviours of a selected physical or abstract system....
. To accomplish this a LVC-IA provides the following:
- IntegrationSystem integrationIn engineering, system integration is the bringing together of the component subsystems into one system and ensuring that the subsystems function together as a system...
through simulation equipment, interoperability tools and support personnel. See also Enterprise integrationEnterprise integrationEnterprise integration is a technical field of Enterprise Architecture, which focused on the study of topics such as system interconnection, electronic data interchange, product data exchange and distributed computing environments....
and Enterprise architectureEnterprise architectureAn enterprise architecture is a rigorous description of the structure of an enterprise, which comprises enterprise components , the externally visible properties of those components, and the relationships between them...
. Integration creates network-centricNetwork centricsNetwork Centrics is the emerging discipline of applying and enhancing networking and computing concepts and implementation technologies in a variety of social, business, content distribution, and communication domains involving interactions amongst the domain entities...
linkages to collect, retrieve and exchange dataData exchangeData exchange is the process of taking data structured under a source schema and actually transforming it into data structured under a target schema, so that the target data is an accurate representation of the source data. Data exchange is similar to the related concept of data integration except...
among live instrumentationInstrumentationInstrumentation is defined as the art and science of measurement and control of process variables within a production, or manufacturing area....
, virtual simulators and constructive simulations as well as between the joint military and specific service commandUnited States armed forcesThe United States Armed Forces are the military forces of the United States. They consist of the Army, Navy, Marine Corps, Air Force, and Coast Guard.The United States has a strong tradition of civilian control of the military...
systems. Integration also bridges together data managementEnterprise Information IntegrationEnterprise Information Integration , is a process of information integration, using data abstraction to provide a unified interface for viewing all the data within an organization, and a single set of structures and naming conventions to represent this data; the goal of EII is to get a large set of...
, exercise managementMilitary exerciseA military exercise is the employment of military resources in training for military operations, either exploring the effects of warfare or testing strategies without actual combat...
, exercise collaboration and updating training support systems. - InteroperabilityInteroperabilityInteroperability is a property referring to the ability of diverse systems and organizations to work together . The term is often used in a technical systems engineering sense, or alternatively in a broad sense, taking into account social, political, and organizational factors that impact system to...
through common protocolsCommunications protocolA communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications...
, specifications, standards and interfaces to standardize LVC components and tools for mission rehearsals and trainingTrainingThe term training refers to the acquisition of knowledge, skills, and competencies as a result of the teaching of vocational or practical skills and knowledge that relate to specific useful competencies. It forms the core of apprenticeships and provides the backbone of content at institutes of...
, testingTest (assessment)A test or an examination is an assessment intended to measure a test-taker's knowledge, skill, aptitude, physical fitness, or classification in many other topics . A test may be administered orally, on paper, on a computer, or in a confined area that requires a test taker to physically perform a...
, acquisitionSimulation Based AcquisitionThe Director for Test Systems Engineering and Evaluation , which was disestablished by US Secretary of Defense on 7 June 1999 and part of its functions are now with the Director, Operational Test and Evaluation , commissioned in 1995 a one year study completed in 1996 to assess the effectiveness...
, analysisAnalysisAnalysis is the process of breaking a complex topic or substance into smaller parts to gain a better understanding of it. The technique has been applied in the study of mathematics and logic since before Aristotle , though analysis as a formal concept is a relatively recent development.The word is...
, experimentExperimentAn experiment is a methodical procedure carried out with the goal of verifying, falsifying, or establishing the validity of a hypothesis. Experiments vary greatly in their goal and scale, but always rely on repeatable procedure and logical analysis of the results...
ation, and logisticsLogisticsLogistics is the management of the flow of goods between the point of origin and the point of destination in order to meet the requirements of customers or corporations. Logistics involves the integration of information, transportation, inventory, warehousing, material handling, and packaging, and...
planningStrategic planningStrategic planning is an organization's process of defining its strategy, or direction, and making decisions on allocating its resources to pursue this strategy. In order to determine the direction of the organization, it is necessary to understand its current position and the possible avenues...
. - ComposabilityComposabilityComposability is a system design principle that deals with the inter-relationships of components. A highly composable system provides recombinant components that can be selected and assembled in various combinations to satisfy specific user requirements...
through common and reusableReusabilityIn computer science and software engineering, reusability is the likelihood a segment of source code that can be used again to add new functionalities with slight or no modification...
components and tools such as enterprise after action reviewAfter Action ReviewAn after action review is a structured review or de-brief process for analyzing what happened, why it happened, and how it can be done better, by the participants and those responsible for the project or event. After-action reviews in the formal sense were originally developed by the U.S...
, adapters, correlated terrain databasesDigital elevation modelA digital elevation model is a digital model or 3-D representation of a terrain's surface — commonly for a planet , moon, or asteroid — created from terrain elevation data....
, Multilevel securityMultilevel securityMultilevel security or Multiple Levels of Security is the application of a computer system to process information with different sensitivities , permit simultaneous access by users with different security clearances and needs-to-know, and prevent users from obtaining access to information for...
for multinational playersMultinational forceA Multinational force is a multinational operation which may be defensive, aggressive, or peacekeeping.Multinational forces include:* Multinational Force and Observers * Multinational Force in LebanonNATO:* IFOR* SFOR...
and hardware/software requirements.
History
Prior to 1990, the field of M&S was marked by fragmentation and limited coordination between activities across key communities. In recognition of these deficiencies, Congress directed the Department of Defense (DoD) to “... establish an Office of the Secretary of Defense (OSD) level joint program office for simulation to coordinate simulation policy, to establish interoperability standards and protocols, to promote simulation within the military departments, and to establish guidelines and objectives for coordination [sic] of simulation, wargaming, and training.” (ref Senate Authorization Committee Report, FY91, DoD Appropriations Bill, SR101-521, pp. 154–155, October 11, 1990) Consistent with this direction, the Department of Modleing and Simulation Office (DMSO) was created, and shortly afterwards many DoD Components designated organizations and/or points of contact to facilitate coordination of M&S activities within and across their communities.For over a decade, the ultimate goal of the DoD in M&S is to create a LVC-IA to assembly models and simulations quickly, which create an operationally valid LVC environment to train, develop doctrine and tactics, formulate operational plans and assess warfighting situations. A common use of these LVC environments will promote closer interaction between operations and acquisition communities. These M&S environments will be constructed from composeable
Composability
Composability is a system design principle that deals with the inter-relationships of components. A highly composable system provides recombinant components that can be selected and assembled in various combinations to satisfy specific user requirements...
components interoperating through an integrated architecture. A robust M&S capability enables the DOD to meet operational and support objectives effectively across the diverse activities of the military services, combatant commands and agencies.
The number of available architectures have increased over time. M&S trends indicate that once a community of use develops around an architecture, that architecture is likely to be used regardless of new architectural developments. M&S trends also indicate that few, if any, architectures will be retired as new ones come online. When a new architecture is created to replace one or more of the existing set, the likely outcome is one more architecture will be added to the available set. As the number of mixed-architecture events increase over time, the inter-architecture communication problem increases as well.
M&S has made significant progress in enabling users to link critical resources through distributed architectures.
In the mid 1980s, SIMNET
SIMNET
SIMNET was a wide area network with vehicle simulators and displays for real-time distributed combat simulation: tanks, helicopters and airplanes in a virtual battlefield. SIMNET was developed for and used by the United States military...
became the first successful implementation of a large-scale, real-time, man-in-the-loop simulator networking for team training and mission rehearsal in military operations. The earliest successes that came through the SIMNET program was the demonstration that geographically dispersed simulation systems could support distributed training by interacting with each other across network connections.
The Aggregate Level Simulation Protocol
Aggregate Level Simulation Protocol
The Aggregate Level Simulation Protocol is a protocol and supporting software that enables simulations to interoperate with one another. Replaced by the High Level Architecture , it was used by the US military to link analytic and training simulations.ALSP consists of:#ALSP Infrastructure...
(ALSP) extended the benefits of distributed simulation to the force-level training community so that different aggregate-level simulations could cooperate to provide theater-level experiences for battle-staff training. The ALSP has supported an evolving “confederation of models” since 1992, consisting of a collection of infrastructure software and protocols for both inter-model communication through a common interface and time advance using a conservative Chandy-Misra based algorithm.
At about the same time, the SIMNET protocol evolved and matured into the Distributed Interactive Simulation
Distributed Interactive Simulation
Distributed Interactive Simulation is an IEEE standard for conducting real-time platform-level wargaming across multiple host computers and is used worldwide, especially by military organizations but also by other agencies such as those involved in space exploration and medicine.-History:The...
(DIS) Standard. DIS allowed an increased number of simulation types to interact in distributed events, but was primarily focused on the platform-level training community. DIS provided an open network protocol standard for linking real-time platform-level wargaming simulations.
In the mid 1990s, the Defense Modeling and Simulation Office
Defense Modeling and Simulation Office
The Defense Modeling and Simulation Office is "the catalyst organization for Department of Defense modeling and simulation and ensures that modeling and simulation technology development is consistent with other related initiatives."...
(DMSO) sponsored the High Level Architecture
High Level Architecture
A high-level architecture is a general purpose architecture for distributed computer simulation systems. Using HLA, computer simulations can interact to other computer simulations regardless of the computing platforms...
(HLA) initiative. Designed to support and supplant both DIS and ALSP, investigation efforts were started to prototype an infrastructure capable of supporting these two disparate applications. The intent was to combine the best features of DIS and ALSP into a single architecture that could also support uses in the analysis and acquisition communities while continuing to support training applications.
The DoD test community started development of alternate architectures based on their perception that HLA yielded unacceptable performance and included reliability limitations. The real-time test range community started development of the Test and Training Enabling Architecture (TENA) to provide low-latency, high-performance service in the hard-real-time application of integrating live assets in the test-range setting. TENA, through its common infrastructure, including the TENA Middleware and other complementary architecture components, such as the TENA Repository, Logical Range Archive, and other TENA utilities and tools, provides the architecture and software implementation and capabilities necessary to quickly and economically enable interoperability
among range systems, facilities, and simulations.
Similarly, the U.S. Army started the development of the Common Training Instrumentation Architecture (CTIA) to link a large number of live assets requiring a relatively narrowly bounded set of data for purposes of providing After Action Reviews (AARs) on Army training ranges in the support of large-scale exercises.
Other efforts that make the LVC architecture space more complex include universal interoperability software packages such as OSAMS or CONDOR developed and distributed by commercial vendors.
As of 2010 all of the DoD architectures remain in service with the exception of SIMNET. Of the remaining architectures: CTIA, DIS, HLA, ALSP and TENA, some are in early and growing use (e.g., CTIA, TENA) while others have seen a user-base reduction (e.g., ALSP). Each of the architectures is providing an acceptable level of capability within the areas where they have been adopted. However, DIS, HLA, TENA, and CTIA-based federations are not inherently interoperable with each other. when simulations rely on different architectures, additional steps must be taken to ensure effective communication between all applications. These additional steps, typically involving interposing gateways or bridges between the various architectures, may introduce increased risk, complexity, cost, level of effort, and preparation time. Additional problems extend beyond the implementation of individual simulation events. As a single example, the ability to reuse supporting models, personnel (expertise), and applications across the different protocols is limited. The limited inherent interoperability between the different protocols introduces a significant and unnecessary barrier to the integration of live, virtual, and constructive simulations.
Challenges
The current status of LVC interoperability is fragile and subject to several reoccurring problems that must be resolved (often anew) whenever live, virtual or constructive simulation systems are to be components in a mixed-architecture simulation event. Some of the attendant problems stem from simulation system capability limitations and other system-to-system incompatibilities. Other types of problems arise from the general failure to provide a framework which achieves a more complete semantic-level interoperability between disparate systems. Interoperability, Integration and Composeablity have been identified as the most technical challenging aspects of a LVC-IA since at least 1996. The Study on the Effectiveness of Modeling and Simulation in the Weapon System Acquisition Process identified cultural and managerial challenges as well. By definition a LVC-IA is a socialtechnical systemSociotechnical systems
Sociotechnical systems in organizational development is an approach to complex organizational work design that recognizes the interaction between people and technology in workplaces. The term also refers to the interaction between society's complex infrastructures and human behaviour...
, a technical system that interacts directly with people. The following table identifies the 1996 challenges associated with the technical, cultural and managerial aspects. In addition, the challenges or gaps found in a 2009 study are also included. The table shows there is little difference between the challenges of 1996 and the challenges of 2009.
| Type | 1996 Challenges | 2009 Challenges |
|---|---|---|
| Technical |
|
|
| Cultural |
|
|
| Managerial |
|
|
Approaches to a Solution
A virtual or constructive model usually focuses on the fidelity or accuracy of the element being represented. A live simulation, by definition represents the highest fidelity, since it is reality. But a simulation quickly becomes more difficult when it is created from various live, virtual and constructive elements, or sets of simulations with various network protocols, where each simulation consists of a set of live, virtual and constructive elements. The LVC simulations are socialtechical systems due to the interaction between people and technology in the simulation. The users represent stakeholders from across the acquisition, analysis, testing, training, planning and experimentation communities. M&S occurs across the entire Joint Capabilities Integration Development SystemJoint Capabilities Integration Development System
The Joint Capabilities Integration and Development System, or JCIDS, isthe formal United States Department of Defense procedure which definesacquisition requirements and evaluation criteria for future defenseprograms...
(JCID) lifecycle. See the "M&S in the JCID Process" figure. A LVC-IA is also considered an Ultra Large Scale (ULS) system due to the use by a wide variety of stakeholders with conflicting needs and the continuously evolving construction from heterogeneous parts. By definition, people are not just users but elements of a LVC simulation.
During the development of various LVC-IA environments, attempts to understand the foundational elements of integration, composability and interoperability emerged. As of 2010, our understanding of these three elements are still evolving, just as software development continues to evolve. Consider software architecture; as a concept it was first identified in the research work of Edsger Dijkstra in 1968 and David Parnas in the early 1970s. The area of software architecture was only recently adopted in 2007 by ISO as ISO/IEC 42010:2007. Integration is routinely described using the methods of architectural and software patterns. The functional elements of integration can be understood due to universality of integration patterns, e.g. Mediation
Data transformation
In metadata and data warehouse, a data transformation converts data from a source data format into destination data.Data transformation can be divided into two steps:...
(intra-communication) and Federation
Federation (information technology)
A Federation is multiple computing and/or network providers agreeing upon standards of operation in a collective fashion. The term may be used when describing the inter-operation of two distinct, formally disconnected, telecommunications networks that may have different internal structures...
(inter-communication); process, data synchronization
Synchronization (computer science)
In computer science, synchronization refers to one of two distinct but related concepts: synchronization of processes, and synchronization of data. Process synchronization refers to the idea that multiple processes are to join up or handshake at a certain point, so as to reach an agreement or...
and concurrency pattern
Concurrency pattern
In software engineering, concurrency patterns are those types of design patterns that deal with multi-threaded programming paradigm.Examples of this class of patterns include:* Active Object* Balking pattern* Double checked locking pattern...
s.
A LVC-IA is dependent on the Interoperability and Composability attributes, not just the technical aspects, but the social or cultural aspects as well. There are sociotechnical challenges, as well as ULS system challenges associated with these features. An example of a cultural aspect is the problem of composition validity. In an ULS the ability to control all interfaces to ensure a valid composition is extremely difficult. The VV&A paradigms are challenged to identfy a level of acceptable validity.
Interoperability
The study of interoperability concerns methodologies to interoperate different systems distributed over a network system. Andreas Tolk introduced the Levels of Conceptual Interoperability ModelConceptual interoperability
Conceptual interoperability is a concept in simulation theory.From the early ideas of Harkrider and Lunceford, simulation composability has been studied in more detail...
(LCIM) which identified seven levels of interoperability among participating systems as a method to describe technical interoperability and the complexity of interoperations. Zeigler's Architecture for M&S extends on the three basic levels of interoperability; pragmatic, semantic, and syntactic. The pragmatic level focuses on the receiver’s interpretation of messages in the context of application relative to the sender’s intent. The semantic level concerns definitions and attributes of terms and how they are combined to provide shared meaning to messages. The syntactic level focuses on a structure of messages and adherence to the rules governing that structure. The linguistic interoperability concept supports simultaneous testing environment at multiple levels. The LCIM associate the lower layers with the problems of simulation interoperation while the upper layers relate to the problems of reuse and composition of models. They conclude “simulation systems are based on models and their assumptions and constraints. If two simulation systems are combined, these assumptions and constraints must be aligned accordingly to ensure meaningful results”. This suggests that levels of interoperability that have been identified in the area of M&S can serve as guidelines to discussion of information exchange in general. The Zeigler Architecture provides an architecture description language
Architecture description language
Different communities use the term architecture description language. Some important communities are the system engineering community, the software engineering community and the enterprise modelling and engineering community...
or conceptual model in which to discuss M&S. The LCIM provides a conceptual model as a means to discuss integration, interoperability and composability. The three linguistic elements relates the LCIM to the Ziegler conceptual model. Architectural and structural complexity an area of research in systems theory to measure the cohesion
Cohesion (computer science)
In computer programming, cohesion is a measure of how strongly-related each piece of functionality expressed by the source code of a software module is...
and coupling
Coupling (computer science)
In computer science, coupling or dependency is the degree to which each program module relies on each one of the other modules.Coupling is usually contrasted with cohesion. Low coupling often correlates with high cohesion, and vice versa...
and is based on the metrics commonly used in software development projects. Zeigler, Kim, and Praehofer presents a theory of modeling and simulation which provides a conceptual framework and an associated computational approach to methodological problems in M&S. The framework provides a set of entities and relations among the entities that, in effect, present a ontology of the M&S domain.
Composability
Petty and Weisel formulated the current working definition: "Composability is the capability to select and assemble simulation components in various combinations into simulation systems to satisfy specific user requirements." Both a technical and user interaction is required indicative of a sociotechnical system is involved. The ability for a user to access data or access models is an important factor when considering composability metrics. If the user does not have visibility into a repository of models, the aggregation of models becomes problematic.In Improving the Composability of Department of Defense Models and Simulation, the factors associated with the ability to provide composability are as follows:
- The complexity of the system being modeled. The size (complexity) of the M&S environment.
- The difficulty of the objective for the context in which the composite M&S will be used. The flexibility of exploration, extensibility.
- The strength of underlying science and technology, including standards.
- Human considerations, such as the quality of management, having a common community of interest, and the skill and knowledge of the work force.
LVC requires Integratablity, Interoperability, and Composability
Page et al. suggest defining Integratability contending with the physical/technical realms of connections between systems, which include hardware and firmware, protocols, networks, etc., Interoperability contending with the software and implementation details of interoperations; this includes exchange of data elements via interfaces, the use of middleware, mapping to common information exchange models, etc., and Composability contending with the alignment of issues on the modeling level. As captured, among others, by Tolk, successful interoperation of solutions of LVC components requires integratability of infrastructures, interoperability of systems, and composability of models. LVC Architectures must holistically address all three aspects in well aligned systemic approaches.Economic Drivers
To produce the greatest impact from its investments, the DoD needs to manage its M&S programs utilizing an enterprise-type approach. This includes both identifying gaps in M&S capabilities that are common across the enterprise and providing seed moneys to fund projects that have widely-applicable payoffs, and conducting M&S investment across the Department in ways that are systematic and transparent. In particular, “Management processes for models, simulations, and data that … Facilitate the cost effective and efficient development of M&S systems and capabilities….” such as are cited in the vision statement require comprehensive Departmental M&S best-practice investment strategies and processes. M&S investment management requires metrics, both for quantifying the extent of potential investments and for identifying and understanding the full range of benefits resulting from these investments. There is at this time no consistent guidance for such practice.The development & use costs associated with LVC can be summarized as follows:
- Live - Relatively high cost since it is very human resourceHuman resourcesHuman resources is a term used to describe the individuals who make up the workforce of an organization, although it is also applied in labor economics to, for example, business sectors or even whole nations...
/materielMaterielMateriel is a term used in English to refer to the equipment and supplies in military and commercial supply chain management....
intensive and not particularly repeatable. - Virtual - Relatively medium cost since it is less human resourceHuman resourcesHuman resources is a term used to describe the individuals who make up the workforce of an organization, although it is also applied in labor economics to, for example, business sectors or even whole nations...
/materielMaterielMateriel is a term used in English to refer to the equipment and supplies in military and commercial supply chain management....
intensive, some reuse can occur, and repeatability is moderate. - Constructive - Relatively low cost since it is the least human resourceHuman resourcesHuman resources is a term used to describe the individuals who make up the workforce of an organization, although it is also applied in labor economics to, for example, business sectors or even whole nations...
/materielMaterielMateriel is a term used in English to refer to the equipment and supplies in military and commercial supply chain management....
intensive, reuse is high, and repeatability is high.
In contrast, the fidelity
Fidelity
"Fidelity" is the quality of being faithful or loyal. Its original meaning regarded duty to a lord or a king, in a broader sense than the related concept of fealty. Both derive from the Latin word fidēlis, meaning "faithful or loyal"....
of M&S is highest in Live, lower in Virtual, and lowest in Constructive. As such, DoD
United States Department of Defense
The United States Department of Defense is the U.S...
policy is a mixed use of LVC through the Military Acquisition
Military acquisition
Military acquisition is the bureaucratic management and procurement process dealing with a nation's investments in the technologies, programs, and product support necessary to achieve its national security strategy and support its armed forces...
life cycle, also known as the LVC Continuum. In the LVC Continuum figure to the right, the JCIDS process is related to the relative use of LVC through the Military Acquisition
Military acquisition
Military acquisition is the bureaucratic management and procurement process dealing with a nation's investments in the technologies, programs, and product support necessary to achieve its national security strategy and support its armed forces...
life cycle.
See also
- Simulation Based AcquisitionSimulation Based AcquisitionThe Director for Test Systems Engineering and Evaluation , which was disestablished by US Secretary of Defense on 7 June 1999 and part of its functions are now with the Director, Operational Test and Evaluation , commissioned in 1995 a one year study completed in 1996 to assess the effectiveness...
- Simulation & Modeling for Acquisition, Requirements, and TrainingSimulation & Modeling for Acquisition, Requirements, and TrainingSimulation & Modeling for Acquisition, Requirements, and Training is a program that was discontinued by the United States Army in 2005.All public access to any SMART-related documents were removed at that time but have started to resurface....