Modeling and Simulation Glossary

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Accreditation The official certification that a model or simulation is acceptable for use for a specific purpose.

Accreditation Authority An individual occupying a position with the appropriate rank, grade, responsibility and/or authority to accredit a model, simulation, or federation of models and/or simulations for a particular purpose or purposes.

Accreditation Process The procedure followed by the M&S application sponsor that culminates in the accreditation determination.

Accreditation Sponsor The DoD Component or other organization with the responsibility for accrediting a model, simulation, or federation of models and/or simulations for a specific use or series of uses (e.g., for joint training or a Defense Acquisition Board milestone review))

Accuracy The degree of exactness of a model or simulation, high accuracy implying low error. Accuracy equates to the quality of a result, and is distinguished from precision, which relates to the quality of the operation by which the result is obtained and can be repeated)

Acquisition An M&S Activity that involves the conceptualization, initiation, design, development, test, contracting, production, deployment, logistic support, modification, and disposal of weapons and other systems, supplies, or services to satisfy Department of Defense (DoD) needs intended for use in or in support of military missions.

ActivityIn modeling and simulation, a task that consumes time and resources and whose performance is necessary for a system to move from one event to the next

Activity-Based Simulation A discrete simulation that represents the components of a system as they proceed from activity to activity; for example, a simulation in which a manufactured product moves from station to station in an assembly line

Activity Models Models of the processes that make up the functional activity showing inputs, outputs, controls, and mechanisms through which the processes of the functional activity are (or will be) conducted

Advanced Concept Technology Demonstration (ACTD) Technology demonstrations that are tightly focused on specific military concepts and that provide the incorporation of technology that is still at an informal stage into a warfighting system. The ACTDs have three objectives: a. to have the user gain an understanding of and to evaluate the military utility of concepts before committing to acquisition; b. to develop corresponding concepts of operation and doctrine that make best use of the new capability; and c. to provide the residual operational capability to the forces. ACTDs are of militarily significant scope and of a size sufficient to establish utility

Advanced Distributed Simulation (ADS) A set of disparate models or simulations operating in a common synthetic environment in accordance with the DIS standards. The ADS may be composed of three modes of simulation: live, virtual and constructive which can be seamlessly integrated within a single exercise

Affected Attributes The specific attributes of an object class instance whose value in a federation execution may be affected by that instance's participation in a dynamic interaction with another instance of the same class, or an instance of another object class

Aggregate Level Simulation Protocol (ALSP) A family of simulation interface protocols and supporting infrastructure software that permit the integration of distinct simulations and war games. Combined, the interface protocols and software enable large-scale, distributed simulations and war games of different domains to interact at the combat object and event level. The most widely known example of an ALSP confederation is the Joint/Service Training Confederation that has provided the backbone to many large, distributed, simulation-supported exercises. Other examples of ALSP confederations include confederations of analytical models that have been formed to support U.S. Air Force, U.S. Army, and USTRANSCOM studies

Area Air Defense Commander JHUAPL has developed exciting new simulation technology to support the AADC. The AADC module, developed by Johns Hopkins University's Applied Physics Laboratory, is an afloat theater air and missile defense planning and coordination cell. From the cell, a naval or joint force commander can orchestrate the effective stationing of joint-service air defense weapons afloat and ashore during the critical initial stages of an expeditionary operation by Marine or Army forces. Installation of an AADC system on the Aegis cruiser Shiloh (CG-67) in 1999; the Navy will use it in Fleet Battle Experiments planned in the Pacific. The AADC can quickly plan and coordinate joint air defense operations against enemy aircraft and missile attacks theater-wide. The module, made up of state-of-the-art computers and large-displays, features decision aids and planning tools in the form of Windows-based software that integrates theater-wide sensor information from a variety of sources. The module keeps track of assets to be defended and the location and coverages of available defensive weapons, and models the impact of terrain and weather on weapons coverage. The system provides a coherent theater air picture in the form of three-dimensional depictions of the battle space. "What this gives you," Adm. Murphy told AFJI, "is an extremely capable collaborative planning capability. It's underpinned with a large database, which has computing power on the order of 56 billion instructions per second in terms of its ability to [rapidly model changes in air defense plans]. So it's an incredibly powerful planning tool, as well as gives a great 3-D picture in terms of operational execution, so your situational awareness is exceptionally good

Algorithm A prescribed set of well-defined, unambiguous rules or processes for the solution of a problem in a finite number of steps

Algorithm Checks A rigorous verification of the mathematics of an algorithm to ensure freedom from any errors in the expression (e.g., incorrect signs, incorrect variables applied in the equations, derivation errors) and to ensure that the algorithms are consistent with their stated intents

Analysis The application of the scientific method to support senior leader planning, programming, and acquisition decisionmaking. It is the locus of analytical processes and efforts conducted by core, multitiered analytical bodies and it is grounded in a systemic and logical examination of the intellectual or material whole and its component parts. These analyses examine best available evidence, are always subject to correction or improvement, and undergo oversight and scrutiny at all levels. Their purpose is to quantify, measure, and demonstrate the relative value and risk of individual or competing programs, systems, or policies to Department decisionmakers.

Analytical Model A model consisting of a set of solvable equations; for example, a system of solvable equations that represents the laws of supply and demand in the world market

Architecture The structure of components in a program/system, their interrelationships, and the principles and guidelines governing their design and evolution over time

Applied Guidance and Best Practices (AGP) Policy and guidance provide direction on what needs to be done and how best to do it. As in any technical field, M&S methods and conventions are evolving, and while best practices exist in some specific areas (e.g., VV&A), there are still broad areas that do not yet have well-established or current guidance. As a result, many model and simulation developers and users are unable to leverage the experiences and unique solutions evolved through case studies and hard-won lessons learned. This includes lessons learned in associated fields such as Software Engineering and Systems Engineering. Established, community-developed and consensus-based best practices would enable more efficient planning and employment of models and simulations.

Artificial Intelligence (AI) The effort to automate those human skills that illustrate our intelligence e.g., understanding visual images, understanding speech and written text, problem solving and medical diagnosis

Atmosphere A kind of mission space entity. The mass of air surrounding the earth and the features embedded within it, including clouds, smoke, and fog

Attribute A property or characteristic of one or more entities; for example, COLOR, WEIGHT, SEX. Also, a property inherent in an entity or associated with that entity for database purposes

Attribute Ownership The property of a federate that gives it the responsibility to publish values for a particular object attribute

Attributive Entity An entity that has the same primary key as the parent and additional attributes that eliminate the occurrence of repeating groups in the parent

Authoritative Data Source A data source whose products have undergone producer data verification, validation and certification activities

Automated Forces (AFOR) The most automated of the computergenerated forces which requires little or no human interaction

Automated Information System (AIS) A combination of computer hardware and computer software, data, and/or telecommunications that performs functions such as collecting, processing, storing, transmitting, and displaying information. Excluded are computer resources, both hardware and software, that are: physically part of, dedicated to, or essential in real time to the mission performance of weapon systems; used for weapon system specialized training, simulation, diagnostic test and maintenance, or calibration; or used for research and development of weapon systems

Autonomous A battlefield entity that does not require the presence of another battlefield entity in order to conduct its own simulation in the battlefield environment is said to be autonomous. All Distributed Interactive Simulation compliant battlespace entities are autonomous in that they are responsible for creating their own view of the environment

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Baselining A configuration management term that implies that the item is placed under formal control so that it cannot be changed without going through a formal review process.

Battlefield View A battlefield entity incorporates a direct soldier/machine interface that replicates the soldier/machine interface of the actual battlefield entity. (reference (p)) See: entity perspective

Battlespace Refers both to the physical environment in which the simulated warfare will take place and the forces that will conduct the simulated warfare. All elements that support the front line forces (e.g., logistics, intelligence) are included in this definition of battlespace

Battlespace Data Base Database that defines the specific domain of an engagement. It includes the parametric data needed to generate an operating version of the SIMWORLD. When combined with the SESSION data base (which provides the scenario and other simulation specific data), the BATTLESPACE can generate an exercise. The BATTLESPACE in all capitals is used as a shortened notation for "Battlespace Data Base."

Battlespace Entity A simulation entity that corresponds to actual equipment, supplies, and personnel that can be seen or sensed on a real battlefield

Benchmark The activity of comparing the results of a model or simulation with an accepted representation of the process being modeled

Benchmarking The comparison between a model's output and the outputs of other models or simulations, all of which represent the same input and environmental conditions. (reference (t)) Bit. The smallest unit of information in the binary system of notation Black Box Model A model whose inputs, outputs, and functional performance are known, but whose internal implementation is unknown or irrelevant; for example, a model of a computerized change-return mechanism in a vending machine, in the form of a table that indicates the amount of change to be returned for each amount deposited. Syn: input/output model. Contrast with: glass box model

Boundary Condition The values assumed by the variables in a system, model, or simulation when one or more of them is at a limiting value at the edge of the domain of interest. Contrast with: final condition; initial condition

Broadcast A transmission model in which a single message is sent to all network destinations; i.e., one-to-all. Broadcast is a special case of multicast. Contrast with: multicast; unicast

Browsing Opportunity for users to freely examine and peruse through the contents of a database

Built-in-Simulation A special-purpose simulation provided as a component of a simulation language; for example, a simulation of a bank that can be made specific by stating the number of tellers, number of customers, and other parameters

Built-in-Simulator A simulator that is built-in to the system being modeled; for example, an operator training simulator built into the control panel of a power plant such that the system can operate in simulator mode or in normal operating mode

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Catalogue An enumeration of M&S data, or other items arranged systematically with descriptive details such as setup time, running time, developer, point of contact, etc

Central Station A computer connected to a local area network that transmits/receives simulation management protocol data units at the direction of the simulation manager

Closed-Form Solution A closed-form solution for representing time in dynamic models is a method in which the states or status of resources are described as explicit and computationally tractable functions of time. Thus, the status of a resource at time "t" can be found by evaluating the appropriate function at "t", without having to simulate combat from the start of that combat through time "t"

Code Verification A rigorous audit of all compilable code to ensure that the representations of verified logic have been properly implemented in the computer code

Coenetic VariableIn modeling, a variable that affects both the system under consideration and that system's environment

Cohesion Cohesion refers to the degree to which the contents of a module are logically related

Command and Control (C&C) The area addresses the representation of command and control in M&S to include data, algorithms, models, and simulations which represent planning and execution processes conducted in military organizations.

Common Federation FunctionalityAgreements on common simulation functionality (services and resources) which are finalized among all participants in the federation during the federation development process. Federation members identified during Federation Design will propose opportunities for common services in areas of assigned responsibilities (also established during Federation Design) during federation development for discussion and negotiation among all federation participants. For instance, agreements on common representations of terrain (data, source, resolution, dynamic vs. static), and environment (required types, data sources, resolution, servers), would be negotiated and agreed to, as would any relevant federation-specific algorithms (e.g., extrapolation)

Common-Use M&S M&S applications, services, or materials provided by a DoD Component to two or more DoD Components

Community of Interest A group of people who have common concerns and interests.

Complex DataData that cannot be characterized as a single concept, atomic data element as defined in reference (q). Complex data includes most scientific and technical data. It has been recently categorized by the Complex Data Task Force into: a. highly derived data (e.g., probability hit/kill); b. objects utilizing the concepts of multiple inheritance (e.g., studentassistant is subclass of student class and employee class), multiple root hierarchies (e.g., a tank is a vehicle and a tank is a weapon where "vehicle" and "weapon" are each roots), and polymorphic attributes (e.g., "capacity" for different types of aircraft may mean number of people, pounds of cargo, or gallons of fuel); c. compositions such as command hierarchies, road networks, images (binary large objects), compound documents; and d. artifacts of legacy systems and physical constraints (e.g., aircraft category and mission in one data element, intelligence facility code where the first few bytes define how the rest of the field is used

Component Class An object class which is a component, or part of, a "composite" object which represents a unified assembly of many different object classes. The identification of a Component Class in the object model template (OMT) should include cardinality information

Composability The ability to rapidly select and assemble components to construct meaningful simulation systems to satisfy specific user requirements. Composability includes the framework, body of knowledge, tools, techniques, and standards necessary to enable effective integration, interoperability, and reuse.

Composite Attribute A single attribute that is composed of a specific set of identifiable pieces of information; e.g., an address made up of a street number, city, state, and zip code

Computational Model A model consisting of well-defined procedures that can be executed on a computer; for example, a model of the stock market, in the form of a set of equations and logic rules

Computer Generated Forces (CGF) A generic term used to refer to computer representations of forces in simulations that attempts to model human behavior sufficiently so that the forces will take some actions automatically (without requiring man-in-the-loop interaction). Also referred to as Semi-automated Forces. DoD programs addressing various levels of computer automation of forces include Command Forces, Intelligent Forces, Modular Semi- Automated Forces, Integrated Tactical Environment Management System, and Close Combat Tactical Trainer Semi-Automated Forces

Computer HardwareDevices capable of accepting and storing computer data, executing a systematic sequence of operations on computer data, or producing control outputs. Such devices can perform substantial interpretation, computation, communication, control, or other logical functions

Computer Resources The totality of computer hardware, firmware, software, personnel, documentation, supplies, services, and support services applied to a given effort

Computer Simulation A dynamic representation of a model, often involving some combination of executing code, control/display interface hardware, and interfaces to real-world equipment

Computer Software (or Software) A set of computer programs, procedures, and associated documentation concerned with the operation of a data processing system, e.g., compilers, library routines, manuals, and circuit diagrams

Computer Software Documentation Technical data or information, including computer listings and printouts, which documents the requirements, design, or details of computer software, explains the capabilities and limitations of the software, or provides operation instructions for using or supporting computer software during the software's operational life

Computer War Game A technique by which different concepts, different pieces of hardware, or different military plans can be investigated in a multi-sided confrontation using a computer to generate displays of the battlefield and perform computations of outcomes

Conceptual AnalysisThe step in the federation development and execution process which establishes the conceptual framework for the federation. It feeds the design of the overall federation structure. The conceptual view of the objects and interactions that must be represented in the federation is key to identifying reuse opportunities in established Federation Object Models (FOMs), and high-level representation of the federation scenario refined during Conceptual Analysis also provides the basis for generation of a more detailed scenario instance during Federation Design/Development

Conceptual Model A statement of the content and internal representations which are the user's and developer's combined concept of the model. It includes logic and algorithms and explicitly recognizes assumptions and limitations

Conceptual Model of the Mission Space (CMMS) First abstractions of the real world that serve as a frame of reference for simulation development by capturing the basic information about important entities involved in any mission and their key actions and interactions. They are simulation-neutral views of those entities, actions, and interactions occurring in the real world

Conceptual Schema Descriptive representation of data and data requirements that supports the "logical" view or data administrator's view of the data requirement. This view is represented as a semantic model of the information that is stored about objects of interest to the functional area. This view is an integrated definition of the data that is unbiased toward any single application of data and is independent of how the data is physically stored or accessed

Concrete Model A model in which at least one component represented is a tangible object; for example, a physical replica of a building

Concurrent Engineering Concurrent engineering is a systematic approach to the integrated, concurrent design of products and their related processes, including manufacture and support. This approach is intended to cause the developers, from the outset, to consider all elements of the product life cycle from conception through disposal, including quality, cost, schedule, and user requirements. See also: Integrated Product and Process Development

Condition The values assumed at a given instant by the variables in a system, model, or simulation. See also: final condition; initial condition; state

Conditional Event A sequentially dependent event that will occur only if some other event has already taken place. See also: time-dependent event

Configuration A collection of an item's descriptive and governing characteristics, which can be expressed: a. in functional terms i.e., what performance the item is expected to achieve; and b. in physical terms i.e., what the item should look like and consist of when it is built

Configuration Management (CM) The application of technical and administrative direction and surveillance to identify and document the functional and physical characteristics of a model or simulation, control changes, and record and report change processing and implementation status

Conservative Synchronization A mechanism that prevents a federate from processing messages out of time stamp order. This is in contrast to optimistic synchronization. The Chandry/Misra/ Bryant null message protocol is an example of a conservative synchronization mechanism

ConsistencyData that is maintained so that it is free from variation or contradiction

ConstantA quantity or data item whose value cannot change

Constrained Simulation A simulation where time advances are paced to have a specific relationship to wallclock time. These are commonly referred to as real-time or scaled-real-time simulations. Here, the terms constrained simulation and (scaled) real-time simulation are used synonymously. Human-in-the-loop (e.g., training exercises) and hardware-in-the-loop (e.g., test and evaluation simulations) are examples of constrained simulations

Continuous ModelA mathematical or computational model whose output variables change in a continuous manner. Contrast with: Discrete Model

Continuous Simulation A simulation that uses a continuous model

Control Station Facility that provides the individual responsible for controlling the simulation and also provides the capability to implement simulation control as Protocol Data Units on the Distributed Interactive Simulation network

Controllability In respect to user interface of SAFORs, this is the ability of a user to dynamically change the tactics or behavior of a force during the course of an exercise easily and efficiently. For all exercises this is the ability to stop and restart an exercise from some interim point in time. Cooperative Development. A project in which two or more DoD Components share in domain research, technical studies, or technology development that may result in dissimilar M&S applications

Coordinate Linear or angular quantities which designate the position that a point occupies in a given reference frame or system. Also used as a general term to designate the particular kind of reference frame or system, such as Cartesian coordinates or spherical coordinates

Coordinated Time Advancement A time advancement mechanism where logical clock advances within each federate only occur after some coordination is performed among the federates participating in the execution e.g., to ensure that the federate never receives an event notice in its past. Aggregate Level Simulation Protocol, for example, used coordinated time advancement. (reference (m)) Critical Event Simulation. A simulation that is terminated by the occurrence of a certain event; for example, a model depicting the year-by-year forces leading up to a volcanic eruption, that is terminated when the volcano in the model erupts. See also: time-slice simulation

Corporate-level M&S Management and Governance (MGT) This addresses policy and practices which enable effective management and use of M&S across the Department. This includes business processes, DoD level outreach, and the development of policy and instructions.

Cross-Functional Integration The melding of acquisition functions (such as design analysis with logistics analysis) involving shared modeling and simulation data and information

Cybernetics The study of human control functions and the mechanical and electronic systems designed to replace or emulate them, including computers. "Cyber," as a prefix, denotes anything related to computer environments, especially things that involve extensive interaction by the user

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Data A representation of facts, concepts, or instructions in a formalized manner suitable for communication, interpretation, or processing by humans or by automatic means

Data Administration (DAdm) The responsibility for definition, organization, supervision, and protection of data within an enterprise or organization

Data Administrator (DAd) A person or group that ensures the utility of data used within an organization by defining data policies and standards, planning for the efficient use of data, coordinating data structures among organizational components, performing logical database design, and defining data security procedures. See also: Data Steward

Data Architecture The framework for organizing and defining the interrelationships of data in support of an organization's missions, functions, goals, objectives, and strategies. Data architectures provide the basis for the incremental, ordered design and development of databases based on successively more detailed levels of data modeling

Data Attribute A characteristic of a unit of data such as length, value, or method of representation

Data Center An organization which serves as a conduit between data sources and data customers. The data center may transform these data as necessary to meet the operational requirements, format, security, and data verification, validation, and certification provisions of its sources and supported users

Data Certification The determination that data have been verified and validated. Data user certification is the determination by the application sponsor or designated agent that data have been verified and validated as appropriate for the specific M&S usage. Data producer certification is the determination by the data producer that data have been verified and validated against documented standards or criteria

Data Collection The process of obtaining information that supports a functional activity, or information requirement

Data Dictionary A specialized type of database containing metadata that is managed by a data dictionary system; a repository of information describing the characteristics of data used to design, monitor, document, protect, and control data in information systems and databases; an application of a data dictionary system

Data Dictionary System An automated system such as an IRDS that can support one or more data dictionaries. A system specifically designed for managing a data dictionary. (reference (bb)) Data Element. A basic unit of information having a meaning and subcategories (data items) of distinct units and values (e.g., address)

Data Element Standardization The process of documenting, reviewing and approving unique names, definitions, characteristics and representations of data elements according to established procedures and conventions

Data Entity An object of interest to the enterprise, usually tracked by an automated system

Data Exchange Standard Formally defined protocols for the format and content of data messages used for interchanging data between networked simulation and/or simulator nodes used to create and operate a distributed, time and space coherent synthetic environment

Data Integrity In information processing, the condition in which data is accurate, current, consistent, and complete

Data Logger A device that accepts Protocol Data Units (PDUs) from the network and stores them for later replay on the network in the same time sequence as the PDUs were originally received. See also: Protocol Data Unit

Data Model In a database, the user's logical view of the data in contrast to the physically stored data, or storage structure. A description of the organization of data in a manner that reflects the information structure of an enterprise

Data Qualitycompleteness, relevance, and accessibility that make data appropriate for use. Quality statements are required for source, accuracy (positional and attribute), up-to-dateness/currency, logical consistency, completeness (feature and attribute), clipping indicator, security classification, and releasability

Data RepositoryA specialized database containing information about data, such as meaning, relationships to other data, origin,usage, and format, including the information resources needed by an organization

Data Security The protection of data from accidental or intentional modification or destruction and from accidental or intentional disclosure to unauthorized personnel

Data Source An organization or subject matter expert who, because of either mission or expertise, serves as a data producer

Data Standardization The process of documenting, reviewing, and approving unique names, definitions, characteristics and representations of data according to established procedures and conventions

Data Structure The logical relationships that exist among units of data and the descriptive features defined for those relationships and data units; an instance or occurrence of a data model

Data Synchronization The timing requirements of a data element, or between and/or among data elements

Data Validation The documented assessment of data by subject area experts and its comparison to known values. Data user validation is an assessment as appropriate for use in an intended model. Data producer validation is an assessment within stated criteria and assumptions

Data Value A value associated with a data element. One of the allowable values of a data element

Data Verification Data producer verification is the use of techniques and procedures to ensure that data meets constraints defined by data standards and business rules derived from process and data modeling. Data user verification is the use of techniques and procedures to ensure that data meets user specified constraints defined by data standards and business rules derived from process and data modeling, and that data are transformed and formatted properly

Data Verification, Validation & Certification (VV&C) The process of verifying the internal consistency and correctness of data, validating that it represents real world entities appropriate for its intended purpose or an expected range of purposes, and certifying it as having a specified level of quality or as being appropriate for a specified use, type of use,or range of uses. The process has two perspectives: producer and user process

Database A collection of interrelated data, often with controlled redundancy, organized according to a schema to serve one or more applications; the data are stored so that they can be used by different programs without concern for the data structure or organization. A common approach is used to add new data and to modify and retrieve existing data

Database Administration (DBAdm) The activity responsible for the enforcement of the policies and standards established by the data administrator, to include providing technical support for physical database definition, design, implementation, maintenance, integrity, and security; and coordinating with computer operations technicians, system developers, vendors, and users. Database administration is oriented toward technical support for databases and the effective and efficient use of information technology resources

Database Administrator (DBAd) A person or group that enforces policy of "how," "where," and "in what manner," data is stored and maintained in each database. Provides information to the Data Administrator (DA) on organizational use of data within the subject database

Database Directory A database of entries each of which represents information about a database or a directory of databases. Information includes the name of a database or directory, ownership, point of contact, access path to the database or directory, description of purpose of database

Database Management System (DBMS) A system that provides the functionality to support the creation, access, maintenance, and control of databases, and that facilitates the execution of application programs using data from these databases

Defense Simulation Internet (DSI) A wide-band telecommunications network operated over commercial lines with connectivity to both military and civilian satellites, allowing users to be linked on a world-wide wide-area network. Note: Superceded with Enhanced Internet Protocol Services in the Defense Information System Network (DISN)

Descriptive Model A model used to depict the behavior or properties of an existing system or type of system; for example, a scale model or written specification used to convey to potential buyers the physical and performance characteristics of a computer. Contrast with: prescriptive model

Deterministic Pertaining to a process, model, simulation or variable whose outcome, result, or value does not depend upon chance. Contrast with: stochastic

Deterministic Algorithm A process that yields a unique and predictable outcome for a given set of inputs

Deterministic Model A model in which the results are determined through known relationships among the states and events, and in which a given input will always produce the same output; for example, a model depicting a known chemical reaction. Contrast with: stochastic model

Deterrence (DET) Deterrence refers to a preventive strategy in any contest or conflict where an actor or potential aggressor refrains from acting because of an overt, implied, or inferred threat of unacceptable damage or punishment.

Digital Simulation (l) A simulation that is designed to be executed on a digital system. (2) A simulation that is designed to be executed on an analog system but that represents a digital system . (3) A simulation of a digital circuit. Contrast with: analog simulation. See also: hybrid simulation

Discovery Services A set of services that enables the formulation of search activities within shared space repositories (e.g., catalogs, directories, registries). It provides the means to articulate the required service arguments, provide search service capabilities, locate repositories to search, and return search results.

Discrete Model A mathematical or computational model whose output variables take on only discrete values; that is, in changing from one value to another, they do not take on the intermediate values; for example, a model that predicts an organization's inventory levels based on varying shipments and receipts. Contrast with: continuous model

Discrete Simulation A simulation that uses a discrete model.(references (b) and (c))

Discrete System A system for which the state variables change instantaneously at separated points in time

Distributed Interactive Simulation (DIS) CompatibleTwo or more simulations and/or simulators are DIS compatible if they are DIS compliant and their models and data that send and interpret Protocol Data Units support the realization of a common operational environment among the systems (coherent in time and space)

Distributed Interactive Simulation (DIS)Network Manager. A specified agency with the responsibility to manage the physical network used for distributed simulation. Responsibilities include: ensuring security of network; scheduling of utilization; establishing network priorities; monitoring execution of scheduled usage; coordinating functional, technical, and user communities' network requirements

Distributed Interactive Simulation (DIS) Protocol Data Unit (PDU) A standard that specifies the format and structure in which data will be organized. The general purpose is to facilitate the electronic transfer of data between agencies with software; specifically, DIS PDUs are designed to enable communications between different types of simulators, simulations, and models

DoD Components Referred to as "the DoD Components," are identified as the:
-Office of the Secretary of Defense,
-the Military Departments,
-the Chairman of the Joint Chiefs of Staff,
-the Combatant Commands,
-the Office of the Inspector General of the Department of Defense,
-the Defense Agencies,
-the DoD Field Activities, and
-all other organizational entities in the Department of Defense.

DoD M&S Executive Agent A DoD Component to whom the USD(A&T) has assigned responsibility and delegated authority for the development and maintenance of a specific area of M&S application, including relevant standards and databases, used by or common to many models and simulations

DoD Publications DoD issuances that implement or supplement DoD Directives and Instructions by providing uniform procedures for management or operational systems and disseminating administrative information. DoD Publications include: Catalogs, Directories, Guides, Handbooks, Indexes, Inventories, Lists, Manuals, Modules, Pamphlets, Plans, Regulations, and Standards that implement or supplement DoD Directives or Instructions

Domain The physical or abstract space in which the entities and processes operate. The domain can be land, sea, air, space, undersea, a combination of any of the above, or an abstract domain, such as an n-dimensional mathematics space, or economic or psychological domains

Dynamic Model A model of a system in which there is change, such as the occurrence of events over time or the movement of objects through space; for example, a model of a bridge that is subjected to a moving load to determine characteristics of the bridge under changing stress

Dynamic Natural Environment The natural environment is constantly changing as a result of man-made efforts (battlefield smoke) and natural phenomenon (weather). Incorporating dynamic natural environment into real time simulations provides a more realistic test bed for weapons, equipment, and personnel

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Enterprise An arbitrarily-defined functional and administrative entity that exists to perform a specific, integrated set of missions and achieve associated goals and objectives, encompassing all of the primary functions necessary to perform those missions

Enterprise Model. An information model(s) that presents an integrated top-level representation of processes, information flows, and data

Entity A distinguishable person, place, unit, thing, event, or concept about which information is kept

Entity Perspective The perception of the synthetic environment held by a simulation entity based on its knowledge of itself and its interactions with the other simulation entities. This includes not only its own view of the simulated physical environment (terrain, air, and sea), but also its own view of itself, the other entities in the synthetic environment, and ofthe effects of the other entities on itself and the synthetic environment. Syn: world view

Entity Relationship Diagram (ERD) A graphic representation of a data model.

Environment The texture or detail of the natural domain, that is terrain relief, weather, day, night, terrain cultural features (such as cities or farmland), sea states, etc.; and the external objects, conditions, and processes that influence the behavior of a system (such as terrain relief, weather, day/night, terrain cultural features, etc.)

Environmental Effect The impact that the natural environment or environmental feature has on some component or process in the simulation exercise such as the propagation of energy and image formation, the performance of a weapon system, platform or sensor, or other non-visualized combat process

Environmental Effect Model A numerical model, parametric model, or database for simulating a natural environmental effect on an entity of a simulation exercise, such as a sensor or platform. Environmental Entity. A simulation entity that corresponds to dynamic elements of the natural state of the geographic, atmospheric, and bathyspheric environment, of the synthetic environment, that can be seen or sensed on a real battlefield, for example, craters, smoke, building collapse, weather conditions, and sea state

Environmental Features An individual element of the natural environment (e.g., a rain system, fog, cloud)

Environmental Model A numerical model, parametric model, or database designed to produce an accurate and consistent data set for one or more parameters that characterize the state of the natural environment

Environmental Representation An authoritative representation of all or a part of the natural or man-made environment, including permanent or semi-permanent man-made features

Environmental Simulation A simulation that depicts all or part of the natural or manmade environment of a system; for example, a simulation of the radar equipment and other tracking devices that provide input to an aircraft tracking system

Error Model a. A model used to estimate or predict the extent of deviation of the behavior of an actual system from the desired behavior of the system; for example, a model of a communications channel, used to estimate the number of transmission errors that can be expected in the channel; b. in software evaluation, a model used to estimate or predict the number of remaining faults,required test time, and similar characteristics of a system

Event A change of object attribute value, an interaction between objects, an instantiation of a new object, or a deletion of an existing object that is associated with a particular point on the federation time axis. Each event contains a time stamp indicating when it is said to occur

Event-Oriented Simulation A simulation in which attention is focused on the occurrence of events and the times at which those events occur; for example, a simulation of a digital circuit that focuses on the time of state transition

Executive Council for Modeling and Simulation (EXCIMS) An organization established by the USD(A&T) and responsible for providing advice and assistance on DoD M&S issues. Membership is determined by the USD(A&T) and is at the Senior Executive Service, flag, and general officer level

Exercise Manager Test director or training officer who manages the setup, control, and feedback of a simulation exercise after the computer network is activated. This individual is part of the user organization. Syn: Simulation Manager

Exogenous Variable A variable whose value is determined by conditions and events external to a given model. Syn: external variable. Contrast with: endogenous variable

Expert System An expert system is a knowledge collection combined with an inference engine capable of interpreting queries and chaining together separate items of knowledge to develop new inferences. The knowledge is typically causally represented as a system of rules. In some cases, expert systems can retrace their paths of inference on demand, thus explaining their conclusions and reasoning

Exploitation of Commercial Technology (ECT) This area addresses the application of commercial technology to DoD M&S, including hardware and software. This includes the application or adaptation of gaming technology, advances in user interface devices, visualization hardware and software, and web based technologies.

Extensibility The ability of a data structure to accommodate additional values or iterations of data over time without impacting its initial design

External Schema A logical description of an enterprise that may differ from the conceptual schema upon which it is based in that some entities, attributes, or relationships may be omitted, renamed, or otherwise transformed

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Face Validation The process of determining whether a model or simulation seems reasonable to people who are knowledgeable about the system under study, based on performance. This process does not review the software code or logic, but rather reviews the inputs and outputs to ensure they appear realistic or representative

Fast Time Simulated time with the property that a given period of actual time represents more than that period of time in the system being modeled; for example, in a simulation of plant growth, running the simulation for one second may result in the model advancing time by one full day; that is, simulated time advances faster than actual time; b. the duration of activities within a simulation in which simulated time advances faster than actual time. Contrast with: real time; slow time

Feature A static element of the synthetic environment that exists but does not actively participate in synthetic environment interactions. Features are represented in the implementation environment by cartographic databases that are used by simulation assets. Entities can interact with features (building them, destroying them, colliding with them, etc.), but features are passive in that they do not initiate action. When features are dynamic (e.g., dynamic terrain) they are called environment entities. See: environmental entity; synthetic environment

Federate A member of a High Level Architecture Federation. All applications participating in a Federation are called Federates. This may include federation managers, data collectors, real world ("live") systems (e.g., C4I systems, instrumented ranges, sensors), simulations, passive viewers and other utilities

Federate Time Scaled wallclock time or logical time of a federate, whichever is smaller. Federate time is synonymous with the "current time" of the federate. At any instant of anexecution different federates will, in general, have different federate times

Federation A named set of interacting federates, a common federation object model, and supporting Runtime Infrastructure, that are used as a whole to achieve some specific objective

Federation Element Term applied to an individual model and/or simulation that is part of a federation of models and simulations

Federation Execution The actual operation, over time, of a subset of the federates and the Runtime Infrastucture initialization data taken from a particular federation. It is the step where the executable code is run to conduct the exercise and produce the data for the measures of effectiveness for the federation execution

Federation Execution Data (FED) Information derived from the Federation Object Model (class, attribute, parameter names, etc.). Each federation execution needs one. In the abstract, creation of a federation execution is simply the binding of a federation execution name to a Federation Execution Data. The organization of Federation Execution Data will become the subject of standard so Federate Object Model tools can automatically generate them for any vendor's Runtime Infrastructure

Federation Execution Sponsor Federation development begins with a user and a requirement. The federation execution sponsor is the organization which uses the results and/or products from a specific application of modeling and simulation. It is the group responsible for establishing the need for the development and execution of a federation. They also establish the framework for the Measures of Effectiveness by which the results of the execution are employed

Federation Object Model (FOM) An identification of the essential classes of objects, object attributes, and object interactions that are supported by a High Level Architecture federation. In addition, optional classes of additional information may also be specified to achieve a more complete description of the federation structure and/or behavior

Federation Objective The statement of the problem that is to be addressed by the establishment and execution of a federation. The description of the problem domain implicit in the objectives statement is critical for focusing the domain analysis activities in the conceptual analysis phase. It specifies the top level goals of the federation, and may specify the operational need or shortfall from which federation developers will derive a scenario for the federation execution. The federation objectives drive this specification, as the scenario development phase must utilize the statement of the objectives to generate a viable context for system evaluations intrinsic to the federation objectives. High-level testing requirements implied in the federation objectives may also drive the identification of welldefined "test points" during development of the federation scenario

Federation Required Execution Details (FRED) A global specification of several classes of information needed by the Runtime Infrastructure to instantiate an execution of the federation. Additional execution-specific information needed to fully establish the "contract" between federation members (e.g., publish responsibilities, subscription requirements, etc.) is also documented in the FRED. The set of management requirements provides one source of input to the Federation Required Execution Details specification, which will be recorded in a standardized format

Federation Time The time used to coordinate the activities between federation members. Runtime Infrastructure services are specified in terms of Federation Time and are independent of the discipline used by Federation members to advance to their individual temporal states

Federation Time Axis A totally ordered sequence of values where each value represents an instant of time in the physical system being modeled, and for any two points T1 and T2 on the federation time axis, if T1 < T2, then T1 represents an instant of physical time that occurs before the instant represented by T2. Logical time, scaled wallclock time, and federate time specify points on the federation time axis. The progression of a federate along the federation time axis during the execution may or may not have a direct relationship to the progression of wallclock time

Field Instrumentation An internal or external recording, monitoring, and relaying device employed by live instrumented entities, usually platform, facility, or exercise-unique, and not typically part of the operational system or equipment. These devices provide an independent source of data to assess the performance of operational systems involved in the exercise

Final Condition The values assumed by the variables in a system, model, or simulation at the completion of some specified duration of time. Syn: equilibrium condition. Contrast with: boundary condition; initial condition

Forces and Organizations (FOR) This area addresses the data, algorithms, models, and simulations which represent people, equipment, and associations within military and non-military, forces and organizations

Functional Area A functional area encompasses the scope (the boundaries) of a set of related functions and data for which an OSD Principal Staff Assistant or the Chairman of the Joint Chiefs of Staff has DoD-wide responsibility, authority, and accountability. A functional area (e.g., personnel) is composed of one or more functional activities (e.g., recruiting), each of which consists of one or more functional processes (e.g., interviews). Also known as a business area

Functional Data Administrator (FDAd) A person or group that ensure the utility of data used within the Functional Area by defining data policies and standards, planning for the efficient use of data, coordinating data structures among organizational components, performing logical database design, and defining data security procedures

Functional Process A well-defined (or definable) set of logically related tasks and decisions within a functional activity that use resources to produce products or services

Functional Process Improvement Application of a structured methodology to define a function's "as is" and "to be" environments; current and future mission needs and end user requirements; objectives and a strategy for achieving those objectives; and a program of incremental and evolutionary improvements to processes, data, and supporting Automated Information Systems that are implemented through functional, technical, and economic analysis and decision-making

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Game Theory The study of situations involving competing interests, modeled in terms of the strategies, probabilities, actions, gains, and losses of opposing players in a game. See also: management game; war game; the study of games to determine the probability of winning given various strategies

Gateway A device that connects two systems, especially if the systems use different protocols. For example, a gateway is needed to connect two independent local networks, or to connect a local network to a long-haul network

Generic Domain A domain type where the attribute is constrained only by the data type assigned by the data base management system (DBMS), or implied by the record type in a flat file, whichever is applicable

Generic Element A generic element is the part of a data element that establishes a structure and limits the allowable set of values of a data element. A generic element has no functional or application context other than to define a general class of data and ensure consistency in structure and domain

General-Use M&S Applications Specific representations of the physical environment or environmental effects used by, or common to, many models and simulations; e.g., terrain, atmospheric, or hydrographic effects

Glass Box Model A model whose internal implementation is known and fully visible; for example, a model of a computerized changereturn mechanism in a vending machine, in the form of a diagram of the circuits and gears that make the change. Contrast with: black box model. Syn: white box model

Global Combat Support System (GCSS) Demand driven, joint initiative designed to accelerate delivery of combat support applications and databases (e.g., logistics, engineering, finance, medical) to the warfighter. Focus is on providing user access to these applications from a single workstation

Graphical Model A symbolic model whose properties are expressed in diagrams; for example, a decision tree used to express acomplex procedure. Contrast with: mathematical model; narrative model; software model; tabular model

Greenwich Mean Time (GMT) A measure of time that conforms, within a close approximation, to the mean diurnal rotation of the Earth and serves as the basis of civil time-keeping. Universal time (UT1) is determined from observations of the stars, radio sources, and also from ranging observations of the Moon and artificial Earth satellites. The scale determined directly from such observations is designated Universal Time Observed (UTO); it is slightly dependent on the place of observation. When UTO is corrected for the shift in longitude of the observing station caused by polar motion, the time scale UT1 is obtained. When an accuracy better than one second is not required, Universal Time can be used to mean Coordinated Universal Time (UTC) Also called "Universal Time [Coordinated]" or "Zulu Time."

Ground Truth The actual facts of a situation, without errors introduced by sensors or human perception and judgment

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Heterogeneous Network A collection of simulations with partially consistent behaviors and/or partially correlated data bases. Examples include simulators of different fidelity, mixed virtual and live simulations, and mixes of virtual and constructive simulations

Heuristic Relating to or using a problem-solving technique in which the most appropriate solution of several found by alternative methods is selected at successive stages of a program for use in the next step of the program

Hierarchical Model A model of information in which data are represented as trees of records connected by pointers

Hierarchy Hierarchy is a ranking or ordering of abstractions

High Level Architecture (HLA) Major functional elements, interfaces, and design rules, pertaining as feasible to all DoD simulation applications, and providing a common framework within which specific system architectures can be defined

Higher Order Model (HOM) A computer model representing combat elements, their functions and/or the terrain they operate on in an aggregated manner. A HOM may represent a battalion as a specific entity which is a conglomeration or averaging of the characteristics of its real-world components. "Higher Order" generally refers to echelons battalion and above with greater than 100m resolution, e.g. 3km, and with faster than real-time performance (e.g., days compressed into minutes, hours into seconds). See also: war game

Homogeneous Network A network of DIS objects with fully consistent behaviors and fully correlated data bases

Human and Organizational Behavior (HOB) This area addresses data, algorithms, models, and simulations that represent the behavior of individuals and organizations, as well as political, economic, and social phenomena.

Human Factors The discipline or science of studying man-machine relationships and interactions. The term covers all biomedical and psychological considerations; it includes, but is not limited to, principles and applications in the areas of human engineering, personnel selection, training, life support, job performance aids, and human performance evaluation

Human-in-the-Loop (HITL) A model that requires human interaction. See: interactive model

Human-Machine Simulation A simulation carried out by both human participants and computers, typically with the human participants asked to make decisions and a computer performing processing based on those decisions

Hybrid Simulation A simulation that combines constructive, live, and/or virtual simulations, typically in a distributed environment. Such simulations typically combine simulators with actual operational equipment, prototypes of future systems, and realistic representations of operational environments

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Iconic Model A physical model or graphical display that looks like the system being modeled; for example, a non-functional replica of a computer tape drive used for display purposes. See also: scale model

Identity Simulation A simulation in which the roles of the participants are investigated or defined; for example, a simulation that identifies aircraft based on their physical profiles, speed, altitude, and acoustic characteristics

Implementation The means by which a synthetic environment, or portions of a synthetic environment, is realized

In-Basket Simulation A simulation in which a set of issues is presented to a participant in the form of documents on which action must be taken; for example, a simulation of an unfolding international crisis as a sequence of memos describing relevant events and outcomes of the participant's actions on previous memos

Independent Time Advancement A means of advancing federate time where advances occur without explicit coordination among federates. Distributed Interactive Simulation is an example of a federation using independent time advancement. (reference (m)) Independent Verification and Validation (IV&V). The conduct of verification and validation of a model or simulation by individuals or agencies that did not develop the model or simulation

Information Any communication or reception of knowledge such as facts, data, or opinions, including numerical, graphic, or narrative forms, whether oral or maintained in any medium, including computerized databases, paper, microform, or magnetic tape

Information Management (IM) The creation, use, sharing, and disposition of data or information as corporate resources critical to the effective and efficient operation of functional activities consistent with Information Management guidance issued by the Office of the Secretary of Defense. Information Management includes the structuring of functional management improvement processes by the Office of the Secretary of Defense Principal Staff Assistants to produce and control the use of data and information in functional activities; information resourcesmanagement; and supporting information technology and information services

Information Model A model that represents the processes, entities, information flows, and elements of an organization and all relationships between these factors. (reference (q)) Information Resource Dictionary System (IRDS). A set of standard specifications for a data dictionary system resulting from U.S. Federal and national standards efforts; a computer system conforming to those standards that provides facilities for recording, storing, and processing descriptions of an organization's significant information and information processing resources

Information Operations (IOP) This area addresses data, algorithms, models, and simulations which represent the spectrum of information operations, including offensive, defensive, and cyber warfare.

Information System (IS) The organized collection, processing, maintenance, transmission, and dissemination of information in accordance with defined procedures, whether automated or manual

Information Technology (IT) The hardware and software used in connection with government information, regardless of technology involved, whether computers, communications, micrographics, or others

Information Warfare (IW) Actions taken to achieve information superiority by affecting adversary information, information-based processes, information systems, and computer-based networks, while defending one's own information, information-based processes, information systems, and computer-based networks

Infrastructure An underlying base or foundation; the basic facilities, equipment, and installations needed for the functioning of a system. See: M&S infrastructure

Instructional Simulation A simulation intended to provide a simulation equivalent of a real or hypothesized stimulus that could occur in the synthetic environment for the purpose of training

Integrated Product and Process Development (IPPD) An approach to systems acquisition that brings together all of the functional disciplines required to develop, design, test, produce and field a system. This is essentially the same as Concurrent Engineering

Integrated Product Team (IPT) Integrated Product Teams are a means to achieve concurrent engineering or Integrated Product and Process Development. They are multi-disciplinary teams consisting of representatives from all disciplines involved in the system acquisition process, from requirements development through disposal. Having the participation of all the appropriate disciplines, Integrated Product Teams are often empowered to make decisions to achieve successful development of their particular product

Intelligence (INT) Intelligence representation in M&S includes portrayal of the processes and systems used for collection, processing, integration, analysis, evaluation, and interpretation of available information concerning foreign nations or actors.

Intelligence Community Coordinating Group (ICCOG) Serves as the intelligence community's forum for M&S exchange, fostering improved communication among community and other government agencies and industry. The Intelligence Community Coordinating Group promotes sharing programs, methodologies, tools, techniques, data and other information

Intelligent Agent A software entity that carries out a set of operations on behalf of a user with some degree of independence or autonomy, and in so doing, employs knowledge or representation of the user's goals or desires

Intelligent Forces (IFOR) A specific program funded by Defense Research Projects Agency to build a maximum of intelligence into the computer representations of forces

Interaction Parameters The information associated with an interaction which objects potentially affected by the interaction must receive in order to calculate the effects of that interaction on its current state

Interactive Model A model that requires human participation. Syn: human-in-the-loop

Internal Schema An internal schema describes data as it is physically stored and includes all aspects of the environment in which a database is to reside

Interval-Oriented Simulation A continuous simulation in which simulated time is advanced in increments of a size suitable to make implementation possible on a digital system

Irregular Warfare (IWF) Irregular warfare can be seen as a violent or insidious struggle among state and non-state actors for legitimacy and influence. The representation of IWF in models and simulations favors indirect and asymmetric approaches, though it may employ the full range of military and other capabilities, in order to erode an adversary's power, influence and will.
Joint Irregular Warfare includes all forms of national power: diplomatic, informational, military and economic (DIME). The DIME actions will affect the political, military, economic, social, information and infrastructure (PMESII) of the adversary.

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Joint M&S Representations of joint and Service forces, capabilities, equipment, materiel, and services used by the Joint community or by two, or more, Military Services. (reference (f) JM&S Proponent. The joint Component responsible for life cycle management of a JM&S application or data base

Joint Modeling and Simulation Executive Panel (JMSEP) An organization responsible for providing advice and assistance on joint M&S issues. The joint Components provide representatives. Membership is at the 0-6 level or higher. The Deputy Director for Wargaming, Simulation, and Operations, J-8, serves as the chair

Joint Modeling and Simulation Investment Plan (JMSIP) A joint Components plan, published under the authority of the Chairman of the Joint Chiefs of Staff and with the coordination of the joint Components, that establishes short-term (present to 6 years) and long-term (beyond 6 years) programs and funding for joint and common use JM&S to achieve the specified goals and objectives outlined in the JM&S Master Plan

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Knowledge The rules, environment, etc. that form the structure humans use to process and relate to information, or the information a computer system must have to behave in an apparently intelligent manner.

Knowledge-Based System A system in which the domain knowledge is explicit and separate from the system's operational instructions/information.

Known Object An object is known to a federate if the federate is reflecting or updating any attributes of that object

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Live Entity A perceptible object that can appear in the virtual battlespace but is unaware and non-responsive (either by intent, lack of capability or circumstance) to the actions of virtual entities. See also: field instrumentation. (reference (b)) Live Simulation. One of several categories of simulation. See Live, Virtual, and Constructive Simulation. (reference (g)) Live, Virtual, and Constructive Simulation. The categorization of simulation into live, virtual, and constructive is problematic, because there is no clear division between these categories. The degree of human participation in the simulation is infinitely variable, as is the degree of equipment realism. This categorization of simulations also suffers by excluding a category for simulated people working real equipment (e.g., smart vehicles)

Local Area Network A class of data network that provides high data rate interconnection between network nodes in close physical proximity

Logical Data Model A model of the data stores and flows of the organization derived from the conceptual business model

Logical Time A federate's current point on the logical time axis. If the federate's logical time is T, all time stamp ordered messages with time stamp less than T have been delivered to the federate, and no time stamp ordered messages with time stamp greater than T have been delivered; some, though not necessarily all, time stamp ordered messages with time stamp equal to T may also have been delivered. Logical time does not, in general, bear a direct relationship to wallclock time, and advances in logical time are controlled entirely by the federates and the Runtime Infrastructure. Specifically, the federate requests advances in logical time via the Time Advance Request and Next Event Request Runtime Infrastructure services, and the Runtime Infrastructure notifies the federate when it has advanced logical time explicitly through the Time Advance Grant service, or implicitly by the time stamp of time stamp ordered messages that are delivered to the federate. Logical time (along with scaled wallclock time) is used to determine the current time of the federate (see definition of federate time). Logical time is only relevant to federates using time stamp ordered message delivery and coordinated time advances, and may be ignored (by requesting a time advance to "infinity" at the beginning of the execution) by other federates

Logical Time Axis A set of points (instants) on the federation time axis used to specify before and after relationships among events

Logical Verification The identification of a set of assumptions and interactions for which the M&S correctly produces intended results. It determines the appropriateness of the M&S for a particular application and ensures that all assumptions and algorithms are consistent with the conceptual M&S

Logistics (LOG) This area addresses the representation of logistics, defined in as the science of planning and carrying out the movement and maintenance of forces. In its most comprehensive sense, those aspects of military operations that deal with design and development, acquisition, storage, movement, distribution, maintenance, evacuation, and disposition of materiel; movement, evacuation, and hospitalization of personnel; acquisition or construction, maintenance, operation, and disposition of facilities; and acquisition or furnishing of services (Joint Pub 1-02).

Long-Haul Network (LHN) A communications network of devices which are separated by substantial geographical distance. A LHN could be any of numerous networks available commercially or through the government that can accommodate the requirements of the DIS virtual battlefield for long distance network services. Also called Wide Area Network. See: wide area network

Lookahead A value used to determine the smallest time stamped message using the time stamp ordered service that a federate may generate in the future. If a federate's current time (i.e., federate time) is T, and its lookahead is L, any message generated by the federate must have a time stamp of at least T+L. In general, lookahead may be associated with an entire federate (as in the example just described), or at a finer level of detail e.g., from one federate to another, or for a specific attribute. Any federate using the time stamp ordered message delivery service must specify a lookahead value

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Management Game A simulation game in which participants seek to achieve a specified management objective given pre-established resources and constraints; for example, a simulation in which participants make decisions designed to maximize profit in a given business situation and a computer determines the results of those decisions. See also: war game

Markov Chain Model A discrete, stochastic model in which the probability that the model is in a given state at a certain time depends only on the value of the immediately preceding state. Syn: Markov model. See also: semi-Markov model

Markov Process A stochastic process that assumes that in a series of random events, the probability for occurrence of each event depends only on the immediately preceding outcome. See also: semi-Markov process

Mass Storage Refers to any device that can store large amounts of data and retrieve it at some later time, even after system power-down. Mass storage devices are usually categorized in terms of being either on-line storage or off-line storage

Mathematical Model A symbolic model whose properties are expressed in mathematical symbols and relationships; for example, a model of a nation's economy expressed as a set of equations. Contrast with: graphical model; narrative model; software model; tabular model

Mean Solar Time A time measurement where time is measured by the diurnal motion of a fictitious body (called "mean Sun") which is supposed to move uniformly in the celestial Equator, completing the circuit in one tropical year. Often termed simply "mean time." The mean Sun may be considered as moving in the celestial Equator and having a right ascension equal to the mean celestial longitude of the true Sun. At any given instant, mean solar time is the hour angle of the mean Sun. In civil life, mean solar time is counted from the two branches of the meridian through 12 hours; the hours from the lower branch are marked a.m. (ante meridian), and those from the upper branch, p.m. (post meridian). In astronomical work, mean solar time is counted from the lower branch of the meridian through 24 hours. Naming the meridian of reference is essential to the complete identificationof time. The Greenwich meridian is the reference for a worldwide standard of mean solar time called "Greenwich Mean Time" (GMT) or "Universal Time [Coordinated]" (UTC)

Measure of Effectiveness (MOE) A qualitative or quantitative measure of the performance of a model or simulation or a characteristic that indicates the degree to which it performs the task or meets an operational objective or requirement under specified conditions

Measure of Outcome (MOO) Metric that defines how operational requirements contribute to end results at higher levels, such as campaign or national strategic outcomes

Measure of Performance (MOP) Measure of how the system/individual performs its functions in a given environment (e.g., number of targets detected, reaction time, number of targets nominated, susceptibility of deception, task completion time). It is closely related to inherent parameters (physical and structural) but measures attributes of system behavior. See also: measure of effectiveness

Metadata Information describing the characteristics of data; data or information about data; descriptive information about an organization's data, data activities, systems, and holdings

Meta-Knowledge Knowledge about knowledge. Knowledge about the use and control of domain knowledge in an expert or knowledgebased system. Knowledge about how the system operates or reasons. Syn: wisdom

Metamodel A model of a model. Metamodels are abstractions of the M&S being developed which use functional decomposition to show relationships, paths of data and algorithms, ordering, and interactions between model components and subcomponents. Metamodels allow the software engineers who are developing themodel to abstract details to a level that subject matter experts can validate

Methodology The system of principles, practices, and procedures, applied to a specific branch of knowledge. Metric A measure of the extent or degree to which a product possesses and exhibits a certain quality, property, or attribute

Metric(s) A process or algorithm that may involve statistical sampling, mathematical computations, and rule-based inferencing. Metrics provide the capability to detect and report defects within a sample

Mission Space The environment of entities, actions, and interactions comprising the set of interrelated processes used by individuals and/organizations to accomplish assigned tasks

Mock-Up A full-sized structural, but not necessarily functional, model built accurately to scale, used chiefly for study, testing, or display. See also: physical model

Model A physical, mathematical, or otherwise logical representation of a system, entity, phenomenon, or process

Modeling Application of a standard, rigorous, structured methodology to create and validate a physical, mathematical, or otherwise logical representation of a system, entity, phenomenon, or process

Modeling and Simulation (M&S) 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

Modeling and Simulation (M&S) Accreditation The official certification that a model or simulation is acceptable for use for a specific purpose

Modeling and Simulation (M&S) Application Sponsor The organization that utilizes the results/product(s) from a specific application of an M&S

Modeling and Simulation (M&S) Developer The agency that actually develops an M&S or the agency that is overseeing the M&S development by a contractor or FFRDC

M&S Activity An M&S procedure or function, involving tasks that consume time and resources, necessary for events or for moving from event to event. M&S Activities include M&S infrastructure management, M&S infrastructure operation, M&S infrastructure design and implementation.

M&S Infrastructure A M&S infrastructure consists of M&S systems and applications, communications, networks, architectures, standards and protocols, and information resource repositories

M&S Interoperability The ability of a model or simulation to provide services to and accept services from other models and simulations, and to use the services so exchanged to enable them to operate effectively together

M&S Resource Services, software, components, federations, adjunct tools, data, interface specifications, design documents, data models, and infrastructures, used in computer-based simulation of operations, or processes which contribute to operations.

Modeling and Simulation Master Plan (MSMP) A DoD plan, published under the authority of the USD(A&T) and with the coordination of the DoD Components, that establishes short-term (present to 6 years) and long-term (beyond 6 years) DoD goals and objectives for the application of M&S for joint and common use within the Department of Defense. It shall also include an assessment of current M&S capabilities, and a road map that delineates the management, investment, and technical strategies required to achieve DoD M&S objectives.

M&S Tools (MST) This area addresses tools and processes that aid in the rapid verification and analysis of simulation inputs and results. This will consider graphic user interfaces and non-model specific graphic tools (including commercial available software).

M&S Working Group (MSWG) The MSWG supports the activities of the Executive Council for Modeling and Simulation and responds to guidance and direction from the USD (A&T). The Director, Defense Modeling and Simulation Office, chairs the MSWG. The membership of the MSWG will normally be 0-6 military officers or GM-15 grade civilians. The MSWG promotes coordination and cooperation of DoD M&S at the working level. Members will represent their organization, serve as the Defense Modeling and Simulation Office point of contact for M&S issues, and prepare their principals for Executive Council for Modeling and Simulation meetings. MSWG membership will mirror the organizational makeup of the Executive Council for Modeling and Simulation; however, other organizations may be added by majority vote of the group, as required

Model-Test-Model An integrated approach to using models and simulations in support of pre-test analysis and planning; conducting the actual test and collecting data; and post-test analysis of test results along with further validation of the models using the test data

Modifier A word that helps define and render a name unique within the database, which is not the prime or class word

Modular Semi-Automated Forces (ModSAF) A class of Computer Generated Forces utilizing a modular software structure in which model components have well-defined and documented interfaces allowing run-time reconfiguration of model behavior to develop generalized, and more sophisticated, representations of reactive behaviors and missions

Monte Carlo Algorithm A statistical procedure that determines the occurrence of probabilistic events or values of probabilistic variables for deterministic models; e.g., making a random draw

Monte Carlo Method In modeling and simulation, any method that employs Monte Carlo simulation to determine estimates for unknown values in a deterministic problem

Monte Carlo Simulation A simulation in which random statistical sampling techniques are employed such that the result determines estimates for unknown values

Multicast A transmission mode in which a single message is sent to selected multiple (but not necessarily all) network destinations; i.e., one-to-many. Contrast with: broadcast, unicast

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Narrative Model A symbolic model the properties of which are expressed in words; for example, a written specification for a computer system. Syn: verbal descriptive model. Contrast with: graphical model; mathematical model; software model; tabular model

Natural Model A model that represents a system by another system that already exists in the real world; for example, a model that uses one body of water to represent another

Net-Centric Environment A framework for full human and technical connectivity and interoperability that allows all DoD users and mission partners to share the information they need, when they need it, in a form they can understand and act on with confidence, and protects information from those who should not have it.

Net-centric Data (NCD) Net-centric Data includes the technology and processes that provide the ability to identify M&S resources, assess whether a resource is appropriate for a given use, and access that resource. DoD's Net-centric Data Strategy is the guiding policy for resource discovery and access, but implementation of that policy for M&S resources is in the early stages. Data mediation is the capability to select data from multiple alternative sources, understand the commonality and differences among data provided by these sources, and transform data from source form to the form required for use.&nbsp; This includes the establishment of standards that enable understandability and reduce the number of data translations.

Network Communication Services The capability provided to electronically transmit modeling and simulation data between networked computational nodes in a manner that meets requirements for transmission latency, multi-cast addressing and security needed to support the creation and operation of distributed time and space coherent synthetic environments

Network Management The collection of administrative structures, policies, and procedures that collectively provide for the management of the organization and operation of the network as a whole. See: network manager

Network Manager The person or organization responsible for maintaining, monitoring and scheduling the operation of the portion of a network used for a distributed simulation and whose responsibilities for the network terminates at the gateways and who is not responsible for the simulation hosts or a local area network. Normally, also in charge of the gateway and not part of the user organization

Network Node A specific network address. See: node. Contrast with: processing node

Network Theory The study of networks used to model processes such as communications, computer performance, routing problems, and project management

Node A general term denoting either a switching element in a network or a host computer attached to a network. See: processing node; network node

Non-kinetic Modeling (NKM) As operational situations and challenges increase in scope and implication, military leaders must often consider how to affect behavioral perceptions and resolve without resorting to the violence and consequences of kinetic weapons. M&S must address non-kinetic activities ranging from deterrence and diplomatic options to security and reconstruction operations, and the consequences of their effect on forces and populations.

Non-Standard Data Element Any data element that exists in a system or application program and does not conform to the conventions, procedures, or guidelines established by the organization

Normative Model A model that makes use of a familiar situation to represent a less familiar one; for example, a model that depicts the human cardiovascular system by using a mechanical pump, rubber hoses, and water. (references (b) and (c)) Notional Data. Speculative or theoretical data rather than actual data

Numerical Model a. A mathematical model in which a set of mathematical operations is reduced to a form suitable for solution by simpler methods such as numerical analysis or automation; for example, a model in which a single equation representing a nation's economy is replaced by a large set of simple averages based on empirical observations of inflation rate, unemployment rate, gross national product, and other indicators; b. A model whose properties are expressed by numbers

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Object A fundamental element of a conceptual representation for a federate that reflects the "real world" at levels of abstraction and resolution appropriate for federate interoperability. For any given value of time, the state of an object is defined as the enumeration of all its attribute values

Object-Based A software design methodology adhering to only some of the properties of object-oriented software; for example, Ada does not support inheritance, a key property of object oriented systems, therefore Ada is often referred to as an object based language. See: object-oriented

Object Model A specification of the objects intrinsic to a given system, including a description of the object characteristics (attributes) and a description of the static and dynamic relationships that exist between objects

Object Model Framework The rules and terminology used to describe High Level Architecture object models

Object Ownership Ownership of the ID attribute of an object, initially established by use of the Instantiate Object interface service. Encompasses the privilege of deleting the object using the Delete Object service. Can be transferred to another federate using the attribute ownership management services

Object-Oriented Language A language that best suits an objectoriented decomposition of software and that provides the capability to implement classes and objects. Directly supports data abstraction and classes, and provides additional support for inheritance as a means of expressing hierarchies of classes

Object-Oriented Programming Use of a programming system that results in programs organized as cooperative collections of objects, each of which represents an instance of some class, and whose classes are members of class hierarchies as defined by the inheritance mechanism

Occlusion The vision effect of closer objects overlapping or occluding more distant ones, providing visual clues to judge how close objects are from the viewer. Slight head motions provide more information about occlusions

Office of the Secretary of Defense (OSD) Includes the immediate Offices of the Secretary and Deputy Secretary of Defense, the Under Secretaries of Defense, the Director of Defense Research and Engineering, the Assistant Secretaries of Defense (ASDs), the General Counsel of the Department of Defense (GC, DoD), the Assistants to the Secretary of Defense (ATSDs), the OSD Directors, or equivalents, who report directly to the Secretary or the Deputy Secretary of Defense, and such other staff offices as the Secretary of Defense establishes to assist in carrying out assigned responsibilities

Off-Line Storage Devices Off-line storage devices generally are used for data backup and archival applications, using media-like magnetic tapes or removable hard or floppy disks

On-Line Storage Devices On-line storage devices provide more immediate retrieval of data and usually refer to devices such as magnetic or optical hard disk drives

Open System A system in which the components and their composition are specified in a non-proprietary environment, enabling competing organizations to use these standard components to build competitive systems. There are three perspectives on open systems: portability - the degree to which a system component can be used in various environments, interoperability - the ability of individual components to exchange information, and integration - the consistency of the various human-machine interfaces between an individual and all hardware and software in the system

Operational Environment A composite of the conditions, circumstances, and influences that affect the employment of military forces and the decisions of the unit commander. Frequently characterized as permissive, semi-permissive, or nonpermissive

Optimisitic Synchronization A mechanism that uses a recovery mechanism to erase the effects of out-of-order event processing. This is in contrast to conservative synchronization. The Time Warp protocol is an example of an optimistic synchronization mechanism. Messages sent by an optimistic federate that could later be canceled

Orthogonal Pertaining to or composed of right angles. Variables which are orthogonal are mutually independent mathematically. This includes the notion of 'independence' or 'ease of transformation' as used in regard to matrices in multivariate analysis

Outcome-Oriented Simulation A simulation in which the end result is considered more important than the process by which it is obtained; for example, a simulation of a radar system that uses methods far different from those used by the actual radar,but whose output is the same. Contrast with: process-oriented simulation

Output Validation The process of determining the extent to which the output (outcome distributions for the M&S and/or submodels) represent the significant and salient features of distributions or real world systems, events, and scenarios

Owned Attribute An object attribute that is explicitly modeled by the owning federate. A federate that owns an attribute has the unique responsibility to provide values for that attribute to the federation, through the Runtime Infrastructure, as they are produced

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Parallel Processing Multiple processes running on multiple processors simultaneously

Parametric Model A model using parametric equations that may be based on numerical model outputs or fits to semi-empirical data to succinctly describe a particular process, feature, or effect

Petri Net An abstract, formal model of information flow, showing static and dynamic properties of a system; i.e., the petri net is defined by its places, transitions, input function, and output function

Physical Data Model A representation of the technologically independent information requirements in a physical environment of hardware, software, and network configurations representing them in the constraints of an existing physical environment

Physical Model A model whose physical characteristics resemble the physical characteristics of the system being modeled; for example, a plastic or wooden replica of an airplane. A mock-up. See also: iconic model; scale model. Contrast with: symbolic model

Pixel A "picture element," refers to the smallest visual unit in an image on a computer display

Platform A generic term used to describe a level of representation equating to vehicles, aircraft, missiles, ships, fixed sites, etc., in the hierarchy of representation possibilities. Other representation levels include units (made up of platforms) and components or modules (which make up platforms)

Polygon A flat plane figure with multiple sides, the basic building block of virtual worlds. The more polygons a computer can display and manipulate per second, the more realistic the virtual world will appear. Humans perceive the equivalent of 80million polygons at more than 30 frames per second in normal vision

Predictive Model A model in which the values of future states can be predicted or are hypothesized; for example, a model that predicts weather patterns based on the current value of temperature, humidity, wind speed, and so on at various locations

Prescriptive Model A model used to convey the required behavior or properties of a proposed system; for example, a scale model or written specification used to convey to a computer supplier the physical and performance characteristics of a required computer. Contrast with: descriptive model

Principal Staff AssistantsThe Under Secretaries of Defense; the Assistant Secretaries of Defense (ASDs); the General Counsel of the Department of Defense (GC, DoD); the Assistants to the Secretary of Defense (ATSDs); and the OSD Directors, or equivalents, who report directly to the Secretary or Deputy Secretary of Defense

Processes Processes affect entities. Attrition, communications, and movement are examples of processes. Processes have a level of detail by which they are described

Process Improvement Modeling Defines and documents the current ("as is") and desired future ("to be") processes and information requirements of a functional activity. Two types of process improvement models are:
a. Activity Models. Models of the processes that make up the functional activity showing inputs, outputs, controls, and mechanisms through which the processes of the functional activity are (or will be) conducted
b. Data Model. In a database, the user's logical view of the data in contrast to the physically stored data, or storage structure. A description of the organization of data in a manner that reflects the information structure of an enterprise

Process Model A model of the processes performed by a system; for example, a model that represents the software development process as a sequence of phases. Contrast with: structural model

Process-Oriented Simulation A simulation in which the process is considered more important than the outcome; for example, a model of a radar system in which the objective is to replicate exactly the radar's operation, and duplication of its results is a lesser concern. Contrast with: outcome-oriented simulation

Processing Node The hardware and software processing resources devoted to one or more simulation entities. See: node

Protocol A set of rules and formats (semantic and syntactic) that define the communication behavior of simulation applications

Protocol Data Unit (PDU) Distributed Interactive Simulation terminology for a unit of data that is passed on a network between simulation applications

Protocol Data Unit (PDU) Standards Formally defined data exchange standards established for each of the several primary classes of functionality that is represented in the DIS synthetic environment; e.g., movement, weapons, firing effects, collisions, etc

Protocol Entity An object that exchanges information with other protocol entities in a network via Protocol Data Units in accordance with an established protocol. A key attribute of a protocol entity is its state. State transitions occur in a given protocol entity in accordance with the established protocol as the result of: a. Protocol Data Units received from other protocol entities, and b. occurrence of an external event (e.g., expiration of a time-out counter.) See also: Protocol Data Unit

Protocol Suite A defined set of complementary protocols within the communication architecture profile

Prototype A preliminary type, form, or instance of a system that serves as a model for later stages or for the final, complete version of the system

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Qualitative Data A data value that is a non-numeric description of a person, place, thing, event, activity, or concept

Quality Assurance (QA) The policies, procedures and systematic actions established in an enterprise for the purpose of providing and maintaining some degree of confidence in data integrity and accuracy throughout the life cycle of the data. The planned systematic activities necessary to ensure that a component, module, or system conforms to established technical requirements

Quantitative Data Numerical expressions that use Arabic numbers, upon which mathematical operations can be performed

Queue In queuing theory, a set of zero or more entities waiting to be serviced by a service facility. (references (b) and (c)) Queuing Model. A model consisting of service facilities and entities waiting in queues to be served; for example, a model depicting teller windows and customers at a bank

Queuing Network Model A model in which a process is described as a network in which each node represents a service facility rendering a given type of service and a queue for holding entities waiting to be served; for example, a model depicting a network of shipping routes and docking facilities at which ships must form queues in order to unload their cargo

Queuing Theory The study of queues and the performance of systems that service entities that are organized into queues. See also: queuing model; queuing network model

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Random Pertaining to a process or variable whose outcome or value depends on chance or on a process that simulates chance, often with the implication that all possible outcomes or values have an equal probability of occurrence; for example, the outcome of flipping a coin or executing a computer-programmed random number generator

Real-Time In modeling and simulation, simulated time advances at the same rate as actual time; for example, running the simulation for one second results in the model advancing time by one second. Contrast with: fast time; slow time

Real-Time Service A service that satisfies timing constraints imposed by the service user. The timing constraints are user specific and should be such that the user will not be adversely affected by delays within the constraints

Real-Time Simulation Same as constrained simulation

Real-Time System A system that computes its results as quickly as they are needed by a real-world system. Such a system responds quickly enough that there is no perceptible delay to the human observer. In general use, the term is often perverted to mean within the patience and tolerance of a human user

Real-World The set of real or hypothetical causes and effects that simulation technology attempts to replicate. When used in a military context, the term is synonymous with real battlefield to include air, land, and sea combat. Syn: real battlefield

Real-World Time The actual time in Greenwich, England. Syn: sidereal time

Reflected Attribute An object attribute that is represented but not explicitly modeled in a federate. The reflecting federate accepts new values of the reflected attribute as they areproduced by some other federation member and provided to it by the Runtime Infrastructure

Reflected Object An object that is represented but not explicitly modeled in a simulation. The reflecting simulation accepts changes in state of the reflected object as they are produced by some other federation member and provided to it by the Runtime Infrastructure

Reliability Model A model used to estimate, measure, or predict the reliability of a system; for example, a model of a computer system, used to estimate the total down time that will be experienced

Reliable Service A communication service in which the received data is guaranteed to be exactly as transmitted

Remote Entity Approximation (REA) The process of extrapolating and interpolating any state of an entity based on its last known state. This includes dead reckoning and smoothing. Syn: dead reckoning

Requirements Definition and Management (REQ) This section addresses the methods used to document requirements for models or simulations, to provide traceability during model development, and to maintain and manage requirements during the lifecycle.

Research, Development, and Acquisition (RDA) One of the three domains for Army M&S applications. RDA includes all M&S used for design, development, and acquisition of weapons systems and equipment. M&S in the RDA domain are used for scientific inquiry to discover or revise facts and theories of phenomena, followed by transformation of these discoveries into physical representations. RDA also includes test and evaluation (T&E) where M&S are used to augment and possibly reduce the scope of real-world T&E

Resolution The degree of detail and precision used in the representation of real world aspects in a model or simulation. See also: granularity

Retraction An action performed by a federate to unschedule a previously scheduled event. Event retraction is visible to the federate. Unlike "cancellation" that is only relevant to optimistic federates such as Time Warp, "retraction" is a facility provided to the federate. Retraction is widely used in classical event oriented discrete event simulations to model behaviors such as preemption and interrupts

Reuse Reuse encompasses the policy, practices, and the supporting technology that foster the effective reuse of M&S resources to include requirements, conceptual models, software architecture, designs, algorithms, software components, models, simulations, and data.

Right-Hand Rule Positive rotation is clockwise when viewed toward the positive direction along the axis of rotation

Runtime Infrastructure (RTI) The general purpose distributed operating system software which provides the common interface services during the runtime of an High Level Architecture federation

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Scalability The ability of a distributed simulation to maintain time and spatial consistency as the number of entities and accompanying interactions increase

Scale Model A physical model that resembles a given system, with only a change in scale; for example, a replica of an airplane one tenth the size of the actual airplane

Scenario a. Description of an exercise. It is part of the session database that configures the units and platforms and places them in specific locations with specific missions; b. an initial set of conditions and time line of significant events imposed on trainees or systems to achieve exercise objectives

Scenario Development A phase of the development of a federation. In this phase, the federation developer(s) formulate a scenario whose execution and subsequent evaluation will lead toward achieving the study objectives set forth by the federation sponsor. The scenario provides an identification of the major entities that must be represented by the federation, a conceptual description of the capabilities, behavior, and relationships (interactions) between these major entities over time, and a specification of relevant environmental conditions (e.g., terrain, atmospherics). Initial and termination conditions are also provided. The style of format of the scenario documentation (e.g., graphics, tables, text) is entirely at the discretion ofthe federation developer. However, communities of use may wish to establish scenario documentation standards among themselves to facilitate reuse of scenario components. The output of this phase is a functional-level scenario description, which is provided as input to the Conceptual Analysis phase. Certain key activities during Conceptual Analysis may also drive reiterations of the Scenario Development phase

Scheduling an Event Invocation of a primitive (Update Attribute Values, Send Interaction, Instantiate Object, or Delete Object) by a federate to notify the Runtime Infrastructure of the occurrence of an event. Scheduling an event normally results in the Runtime Infrastructure sending messages to other federates to notify them of the occurrence of the event

Schema Descriptive representation of data and/or data requirements that describe conceptual, internal, or external views of information/data needs

Scope Used in reference to SAFOR, scope refers to the aspects of combat portrayed by the system. For example, ground combat, combat support, combat service support, air-to-air combat, airto- ground combat, air-to-ship combat, naval surface combat, naval undersea warfare, deployment

Security (SEC) The ability to control access to information and code maintained in a simulation, whether classified, proprietary, or simply for official use, is a major concern as more exercises use commercial pathways and have agency and coalition participants with different levels of security access.

Segment A portion of a session that is contiguous in simulation time and in wall-clock time (sidereal time)

Selector A portion of an address identifying a particular entity at an address (e.g., a session selector identifies a user of the session service residing at a particular session address)

Semi-Automated Forces (SAFOR) Simulation of friendly, enemy and neutral platforms on the virtual battlefield in which the individual platform simulation are operated by computer simulation of the platform crew and command hierarchy. The term "semi-automated" implies that the automation is controlled and monitored by a human who injects command-level decision making into the automated command process. See also: Computer-Generated Forces

Semi-Markov Model A Markov chain model in which the length of time spent in each state is randomly distributed

Semi-Markov Process A Markov process in which the duration of each event is randomly distributed

Session A portion of an exercise that is contiguous in wallclock (sidereal) time and that is initialized per an exercise database

Shared Space A mechanism that provides data storage and access capabilities for users within a given network space. Enterprise shared space refers to a store of data that is accessible by all users within or across security domains on the GIG. A shared space provides virtual or physical access to any number of data assets (e.g., catalogs, Web sites, registries, classification networks, document storage, and databases). Any user, system, or application that posts data uses shared space.

Sidereal Time Time based upon the rotation of the Earth relative to the vernal equinox. Time that is independent of simulation clocks, time zones, or measurement errors. The "Ground Truth" of time measurement. See also: Real World Time

Simuland The system being simulated by a simulation

Simulated Time Time as represented within a simulation. Syn: virtual time. See also: fast time; real time; slow time

Simulation A method for implementing a model over time

Simulation Application a. The executing software on a host computer that models all or part of the representation of one or more simulation entities. The simulation application represents or "simulates" real-world phenomena for the purpose of training, analysis, or experimentation. Examples include manned vehicle (virtual) simulators, computer generated forces (constructive), environment simulators, and computer interfaces between a Distributed Interactive Simulation network and real (live) equipment. The simulation application receives and processes information concerning entities created by peer simulation applications through the exchange of Distributed Interactive Simulation Protocol Data Units. More than one simulation application may simultaneously execute on a host computer; b. the application layer protocol entity that implements standard Distributed Interactive Simulation protocol

Simulation Entity An element of the synthetic environment that is created and controlled by a simulation application through the exchange of Distributed Interactive Simulation Protocol Data Units (e.g., tanks, submarines, carriers, fighter aircraft, missiles, bridges). It is possible that a simulation application may be controlling more than one simulation entity

Simulation Environment a. Consists of the operational environment surrounding the simulation entities including terrain, atmospheric, bathyspheric and cultural information; b.all the conditions, circumstances, and influences surrounding and affecting simulation entities including those stated in a.

Simulation Game A simulation in which the participants seek to achieve some agreed-upon objective within an established set of rules. For example, a management game, a war game. Note: The objective may not be to compete, but to evaluate the participants, increase their knowledge concerning the simulated scenario, or achieve other goals. Syn: gaming simulation

Simulation Interoperability (SIM) Simulation interoperability encompasses the technology and processes associated with technical and semantic composition of individual simulations and systems with which they must interoperate (e.g., as federations). This includes constructive simulation, virtual simulators, interfaces to live systems, i.e., live-virtual-constructive (LVC), and other interoperability mechanisms.

Simulation Management A mechanism that provides centralized control of the simulation exercise. Functions of simulation management include: start, restart, maintenance, shutdown of the exercise, and collection and distribution of certain types of data

Simulation Object Model (SOM) A specification of the intrinsic capabilities that an individual simulation offers to federations. The standard format in which SOMs are expressed provides a means for federation developers to quickly determine the suitability of simulation systems to assume specific roles within a federation

Simulation Process The imitative representation of the actions of platform(s), munitions(s), and life form(s) by computer program(s) in accordance with a mathematical model and the generation of associated battlefield entities. May be fully automated or partially automated. In the latter case, the humanin- the-loop injects command-level decisions into the process and is not intended to be a "trainee."

Simulation Support Entity Processing modules used to support, control, or monitor the simulation environment, but which do not actually exist on the battlefield. This includes battlefield viewing devices for controllers or exercise observers such as the stealth vehicle, the plan view display, after action review systems, and simulation control systems

Simulation Time a. A simulation's internal representation of time. Simulation time may accumulate faster, slower, or at the same pace as sidereal time; b. The reference time (e.g., Universal Coordinated Time) within a simulation exercise, this time is established by the simulation management function before the start of the simulation and is common to all participants in a particular exercise

Simulator a. A device, computer program, or system that performs simulation; b. For training, a device which duplicatesthe essential features of a task situation and provides for direct human operation

Single Point-of-Entry The organization (s) responsible for entering data values for a data element. (reference (j)) Six Degrees of Freedom (6 DOF). Refers to the number of simultaneous directions or inputs a sensor can measure. Typically used to describe the combination of spatial positions (X, Y, Z) and orientation (roll, pitch, yaw)

Slow Time The duration of activities within a simulation in which simulated time advances slower than actual time

Smoothing Interpolation of the previous state of an entity (location, velocity, etc.) to the current state, creating a smoothed transition between two successive entity state updates

Span The scale of the domain that is global, theater, regional, local, individual. Description of the span is often subjective.

Stability Constancy of purpose; steadfastness; reliability; dependability

Stabilized-Variable Model A model in which some of the variables are held constant and the others are allowed to vary; for example, a model of a controlled climate in which humidity is held constant and temperature is allowed to vary

Standard A rule, principle, or measurement established by authority, custom, or general consent as a representation or example

Standards Development & Coordination (SDC) Existing standards processes, e.g. Defense Standardization Program (DSP), and standards policy bodies such as the Object Management Group (OMG), Simulation Interoperability Standards Organization (SISO), Institute of Electrical and Electronics Engineers (IEEE), International Standards Organization (ISO), North Atlantic Treaty Organization (NATO) can be used to bring products to standard. M&S standards initiatives across the Department must be coordinated and a process developed to facilitate lifecycle sustainment.

State a. The internal status of a simulation entity; e.g. fuel level, number of rounds remaining, location of craters, etc. b. a condition or mode of existence that a system, component, or simulation may be in; for example, the pre-flight state of an aircraft navigation program or the input state of given channel; c. the values assumed at a given instant by the variables that define the characteristics of a system, component, or simulation. Syn: system state. See also: final state; initial state; steady state

State Transition A change from one state to another in a system, component, or simulation

State Variable A variable that defines one of the characteristics of a system, component, or simulation. The values of all such variables define the state of the system, component, or simulation

Static Model A model of a system in which there is no change; for example, a scale model of a bridge, studied for its appearance rather than for its performance under varying loads

Steady State A situation in which a model, process, or device exhibits stable behavior independent of time

Stealth Viewer A component that provides the capabilities for visually observing a Distributed Interactive Simulation exercise without participating in the Distributed Interactive Simulation exercise interaction

Stimulate To provide input to a system in order to observe or evaluate the system's response

Stimulation Stimulation is the use of simulations to provide an external stimulus to a system or subsystem. An example is the use of a simulation representing the radar return from a target to drive (stimulate) the radar of a missile system within a hardware/software-in-the-loop simulation

Stimulator a. A hardware device that injects or radiates signals into the sensor system(s) of operational equipment to imitate the effects of platforms, munitions, and environment that are not physically present; b. a battlefield entity consisting of hardware and/or software modules that injects signals directly into the sensor systems of an actual battlefield entity to simulate other battlefield entities in the virtual battlefield

Stochastic Pertaining to a process, model, or variable whose outcome, result, or value depends on chance. Contrast with: deterministic

Stochastic Model A model in which the results are determined by using one or more random variables to represent uncertainty about a process or in which a given input will produce an output according to some statistical distribution; for example, a model that estimates the total dollars spent at each of the checkout stations in a supermarket, based on probable number of customers and probable purchase amount of each customer. Syn: probabilistic model

Stochastic Process Any process dealing with events that develop in time or cannot be described precisely, except in terms of probability theory

Structural Model A representation of the physical or logical structure of a system; for example, a representation of a computer network as a set of boxes connected by communication lines. Contrast with: process model

Structural Validation. The process of determining that the M&S assumptions, algorithms, and architecture provide an accurate representation of the composition of the real world as relevant to the intended use of the M&S

Subject Area A major, high-level classification of data. A group of entity types that pertain directly to a function or major topic of interest to the enterprise

Symbolic Model A model whose properties are expressed in symbols. Examples include graphical models, mathematical models, narrative models, software models, and tabular models. Contrast with: physical model

Synthetic Environments (SE) Internetted simulations that represent activities at a high level of realism from simulations of theaters of war to factories and manufacturing processes. These environments may be created within a single computer or a vast distributed network connected by local and wide area networks and augmented by super-realistic special effects and accurate behavioral models. They allow visualization of and immersion into the environment being simulated

System A collection of components organized to accomplish a specific function or set of functions. (reference (c))

Systems, Systems of Systems, and Families of Systems (SYS) Representations of systems, systems of systems (SoS), and Families of Systems (FoS) including data, algorithms, models, and simulations which represent military materiel. The majority of current and foreseeable DoD M&S includes representations of materiel.

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Tabular Model A symbolic model whose properties are expressed in tabular form; for example, a truth table that represents a Boolean logic "OR" function. Contrast with: graphical model; mathematical model; narrative model; software model

Taxonomy A classification system. Provides the basis for classifying objects for identification, retrieval and research purposes

Technical Data Scientific or technical information recorded in any form or medium (such as manuals and drawings). Computer programs and related software are not technical data; documentation of computer programs and related software are. Also excluded are financial data or other information related to contract administration

Technical Infrastructure The internal framework that must be built to implement an operational service

Tightly Coupled A condition that exists when simulation entities are involved in very close interaction such that every action of an entity must be immediately accounted for by the other entities. Several tanks in close formation involved rapid, complicated maneuvers over the terrain is an example of a tightly coupled situation

Time The measurable aspect of duration. Time makes use of scales based upon the occurrence of periodic events. These are: the day, depending on the rotation of the Earth; the month, depending on the revolution of the Moon around the Earth; and the year, depending upon the revolution of the Earth around the Sun. Time is expressed as a length on a duration scale measured from an index on that scale. For example: 4 p.m. local mean solar time means that 4 mean solar hours have elapsed since the mean Sun was on the meridian of the observer. (reference (m))Time-Dependent Event. An event that occurs at a predetermined point in time or after a predetermined period of time has elapsed. See also: conditional event. (references (b) and (c)) Time Flow Mechanism. The approach used locally by an individual federate to perform time advancement. Commonly used time flow mechanisms include event driven (or event stepped), time driven, and independent time advance (real-time synchronization) mechanisms

Time Management A collection of mechanisms and services to control the advancement of time within each federate during an execution in a way that is consistent with federation requirements for message ordering and delivery

Time-Slice Simulation a. A discrete simulation that is terminated after a specific amount of time has elapsed; for example, a model depicting the year-by-year forces affecting a volcanic eruption over a period of 100,000 years. Syn: timeinterval simulation. See also: critical event simulation; b. a discrete simulation of continuous events in which time advances by intervals chosen independent of the simulated events; for example, a model of a time multiplexed communication system with multiple channels transmitting signals over a single transmission line in very rapid succession

Time Step Models Dynamic models in which time is advanced by a fixed or independently determined amount to a new point in time, and the states or status of some or all resources are updated as of that new point in time. Typically these time steps are of constant size, but they need not be

Time Variable A variable whose value represents simulated time or the state of the simulation clock

Tracked Munitions A munition for which tracking data is required. By necessity, a tracked munition becomes a simulation entity during its flight; its flight path is represented, therefore, by Entity State Protocol Data Units

Translator The translator is the portion of an actor that interacts with ALSP. Normally, this is new software that adds the ability to transmit information about objects modeled by the actor and to receive information about objects modeled by other actors and to ghost these objects

Transmit Management The control of the transmission rate to match the transmission media. The transmission rate is selected to reduce total network traffic

Transportation Service A Runtime Infrastructure provided service for transmitting messages between federates. Different categories of service are defined with different characteristics regarding reliability of delivery and message ordering

True Global Time A federation-standard representation of time synchronized to Greenwich Mean Time or Universal Time [Coordinated] (as defined in this glossary) with or without some offset (positive or negative) applied

Typing Typing is the enforcement of the class of an object, such that objects of different types may not be interchanged, or may be interchanged only in restricted ways. (reference (d))

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Unbundling The process of unpacking a bundled Protocol Data Unit into multiple separate Protocol Data Units. Contrast with: bundling

Unconstrained Simulation A simulation where there is no explicit relationship between wallclock time and the rate of time advancements. These are sometimes call "as-fast-as-possible" simulations, and these two terms are used synonymously here. Analytic simulation models and many constructive "war game" simulations are often unconstrained simulations

Unit a. An aggregation of entities; b. a basis of measurement

Unit Conversion A system of converting measurement from one basis to another; for example, English/metric, knots/feet per second, etc

Universal Time [Coordinated] (UTC) The same as Greenwich Mean Time. A nonuniform time based on the rotation of the Earth, which is not constant. Usually spoken as, "Coordinated Universal Time."

Universal Space Rectangular (USR) Coordinate System A righthanded orthogonal coordinate system with its origin at the center of the Earth, positive x-axis in the equatorial plane and passing through the zero degree meridian, positive y-axis in the equatorial plane and passing through the ninety degree east meridian, and positive z-axis passing through the North Pole

User Military, industrial, or academic organizations requiring access to the DIS network. Prior to use, they will appoint one point of responsibility for their use of the network. This person is the Exercise Manager. See also: Simulation Manager

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Validation The process of determining the degree to which a model or simulation is an accurate representation of the realworld from the perspective of the intended uses of the model or simulation

Validation Agent The organization designated by the M&S sponsor to perform validation for a model, simulation, or federation of models and/or simulations. See also: verification and validation proponent

Validity The quality of maintained data that is found on an adequate system of classification (e.g., data model) that is rigorous enough to compel acceptance

Variable A quantity or data item whose value can change. See also: dependent variable; independent variable; state variable. Contrast with: constant

Verification The process of determining that a model or simulation implementation accurately represents the developer's conceptual description and specification. Verification also evaluates the extent to which the model or simulation has been developed using sound and established software engineering techniques

Verification Agent The organization designated by the M&S sponsor to perform verification for a model, simulation, or federation of models and/or simulations. See also: verification and validation proponent

Verification and Validation (V&V) Proponent The agency responsible for ensuring verification and validation is performed on a specific model or simulation

Verification, Validation, and Accreditation (VVA) Verification is the process of determining that a model implementation and its associated data accurately represent the developer's conceptual description and specifications. Validation is the process of determining the degree to which a model and its associated data are an accurate representation of the real world from the perspective of the intended uses of the model. Accreditation is the official certification that a model, simulation, or federation of models and simulations and its associated data are fit for a specific purpose. The VV&A area encompasses three main components: the thing to be simulated, i.e. the real world referent; the simulation model; and a bounding principle, i.e. the accuracy required for the intended use

Virtual Refers to the essence or effect of something, not the fact

Virtual Battlespace The illusion resulting from simulating the actual battlespace

Virtual Images Visual, auditory and tactile stimuli that are transmitted to the sensory end organs so they appear to originate from within the three-dimensional space surrounding the user

Virtual Network The interconnection of Distributed Interactive Simulation cells by any communications means that provide thenecessary network services to conduct an exercise

Virtual Prototype A model or simulation of a system placed in a synthetic environment, and used to investigate and evaluate requirements, concepts, system design, testing, production, and sustainment of the system throughout its life cycle

Virtual Reality The effect created by generating an environment that does not exist in the real world. Usually, a stereoscopic display and computer-generated three-dimensional environment giving the immersion effect. The environment is interactive, allowing the participant to look and navigate about the environment, enhancing the immersion effect. Virtual environment and virtual world are synonyms for virtual reality

Visualization The formation of an artificial image that cannot be seen otherwise. Typically, abstract data that would normally appear as text and numbers is graphically displayed as an image. The image can be animated to display time varying data

Visual Stealth A component that provides the capabilities for visually observing a Distributed Interactive Simulation exercise without participating in the Distributed Interactive Simulation exercise interaction

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Wallclock Time A federate's measurement of true global time, where the measurement is typically output from a hardware clock. The error in this measurement can be expressed as an algebraic residual between wallclock time and true global time or as an amount of estimation uncertainty associated with the wallclock time measurement software and the hardware clock errors

Warfare Simulation A model of warfare or any part of warfare for any purpose (such as analysis or training)

War Game A simulation game in which participants seek to achieve a specified military objective given pre-established resources and constraints; for example, a simulation in which participants make battlefield decisions and a computer determines the results of those decisions. See also: management game. Syn: constructive simulation; higher order model

Weapons of Mass Destruction (WMD) This area addresses data, algorithms, models, and simulations which represent the effects of chemical, biological, radiological, nuclear, and (high) explosive weapons.

Workforce Development (WFD) DoD personnel must be adept at employing models, simulations and data to support DoD objectives. This area includes special M&S training, advanced M&S, and educational opportunities to enhance users or managers of M&S.

World Coordinate System The right-handed geocentric Cartesian system. The shape of the world is described by the World Geodetic System 1984 standard. The origin of the world coordinate system is the centroid of the earth. The axes of this system are labeled X, Y, and Z, with: the positive X-axis passing through the Prime Meridian at the Equator; the positive Y-axis passing through 90 degrees East longitude at the Equator; and the positive Z-axis passing through the North Pole

World Geodetic System 1984 (WGS 84) A geocentric coordinate system which describes a basic frame of reference and geometric figure for the Earth, and which models the Earth from a geometric, geodetic, and gravitational standpoint. The WGS 84 coordinate system origin and axes also serve as the x, y, and z axes of the WGS 84 ellipsoid, the z axis being the rotational axis

World View The view each simulation entity maintains of the simulated world from its own vantage point, based on the results of its own simulation and its processing of event messages received from all external entities. For Computer Generated Forces and for manned simulators or real vehicles, the world view is the perceptions of the participating humans

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