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Systems Modeling & Simulation Working Group

The following was compiled by members of the Systems Modeling & Simulation Working Group to provide the model-based systems engineering community with a common set of shared terms and definitions.

A-C | D-F | G-I | J-L | M-O | P-R | S-U | V-X | Y-Z

Terms & Definitions (A-C)


Term Definition Source
Abstraction The process of selecting the essential aspects of a simuland to be represented in a model or simulation while excluding those aspects that are not relevant to the purpose of the model or simulation. The set of elements produced by this process. Modeling & Simulation Coordination Office
Accuracy The degree to which a parameter or variable, or set of parameters or variables, within a model or simulation conforms to a true value, standard or referent. Modeling & Simulation Coordination Office
Acquirer The stakeholder that acquires or procures a product or service from a supplier
Acquisition The process of obtaining a system, product or service. ISO/IEC 2008
Activity A set of actions that consume time and resources and whose performance is necessary to achieve, or contribute to, the realization of one or more outcomes
Activity Model A process model that describes the functional activity under examination in terms of inputs, transforms, outputs, and controls. Modeling & Simulation Coordination Office
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. (IEEE Std 610.3-1989) Modeling & Simulation Coordination Office
Adaptive System A system that is able to modify its behavior according to changes in its external environment or internal components of the system itself. Modeling & Simulation Coordination Office
Agent A computer system capable of autonomous action - of deciding for itself what behaviors are needed to satisfy its design objectives, and capable of interacting with other agents (e.g., a 3D character that exhibits human or human-like behavior). Modeling & Simulation Coordination Office
Agent-Based Simulation A simulation that focuses on the implementation of agents and the sequence of actions and interactions of the agents over periods of time. Modeling & Simulation Coordination Office
Aggregate (Unit) A group of entities or a group of other aggregates considered as a single unit. The substitution of the word "unit" is used to avoid phrases like "aggregate aggregate." (IEEE Std 1278.1-2012) Modeling & Simulation Coordination Office
Aggregate Level Simulation Protocol (ALSP) A family of simulation interface protocols and supporting infrastructure software that permit the integration of distinct simulations and game scenarios (like war games). Combined, the interface protocols and software enable large-scale, distributed simulations and game scenarios of different domains to interact at the scenario (like combat) object and event level. Modeling & Simulation Coordination Office
Aggregation The process of grouping entities while preserving the salient effects of entity behavior and interaction while grouped. Contrast with: Disaggregation. Modeling & Simulation Coordination Office
Agile Project execution methods can be described on a continuum from “adaptive” to “predictive.” Agile methods exist on the “adaptive” side of this continuum, which is not the same as saying that agile methods are “unplanned” or “undisciplined.”
Algorithm A procedure or a set of well-defined steps, rules, or processes used to solve a problem. Modeling & Simulation Coordination Office
Analysis The systematic, thoughtful, and rigorous employment of the scientific method to examine a problem, scenario, or issue in order to gain insights into relationships between constituent components, understand underlying principles, or answer a specific set of pre-identified questions. Modeling & Simulation Coordination Office
Analytical Model A model consisting of a set of mathematical equations or logical connections / representation; e.g., a system of solvable equations or logical links that represent a specific behavior of the real worl to be simulated.
Application Lifecycle Management (ALM) Application lifecycle management (ALM) is the product lifecycle management (governance, development, and maintenance) of computer programs. It encompasses requirements management, software architecture, computer programming, software testing, software maintenance, change management, continuous integration, project management, and release management.
Architectures The structure of components in a program/system, their interrelationships, and the principles and guidelines governing their design and evolution over time. (DoDI 5000.70) Modeling & Simulation Coordination Office
Assumption A supposition on the current situation or state of something or a presupposition on the future course of events / behavior, either or both assumed to be true in the absence of positive proof, necessary in the process of planning to complete an estimate of the situation, run a simulation in order to and make a decision on the course of action.
Attribute A property or characteristic of an entity, object or event (e.g., color, weight, sex, time of occurrence). Modeling & Simulation Coordination Office
Attribute Ownership The property of an instance attribute that gives another federate the capability to supply values for that instance attribute during simulation execution. Modeling & Simulation Coordination Office
Augmented Reality A type of virtual reality in which synthetic stimuli are registered with and superimposed on real world objects; often used to make information otherwise imperceptible to human senses perceptible. Modeling & Simulation Coordination Office
Autonomous An entity that can operate independently - without input or guidance from another entity - to achieve objectives within a simulated environment. Modeling & Simulation Coordination Office
Avatar A virtual object used to represent a participant or physical object in a simulation; the (typically visual) representation may take any form. Modeling & Simulation Coordination Office
Behavior For a given object, how attribute value changes affect or are affected by the attribute value changes of itself, other objects, or the simulation environment. Modeling & Simulation Coordination Office
Black Box Model A model whose inputs, outputs, and functional performance are known, but whose internal implementation is unknown or irrelevant. Also see white box model. (IEEE Std 610.3-1989) Modeling & Simulation Coordination Office
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 or a value at the edge of the domain of interest. Also see: Final Condition; Initial Condition. (IEEE Std 610.3-1989) Modeling & Simulation Coordination Office
Capability An expression of a system, product, function or process’ ability to achieve a specific objective under stated conditions.
Capability Maturity Model Integration (CMMI) Is a proven industry framework to improve product quality and development efficiency for both hardware and software. CMMI describes an evolutionary improvement path from ad hoc, immature processes to disciplined, mature processes with improved quality and effectiveness. CMMI
Cave Automatic Virtual Environment (Cave) A mechanism for manifesting a virtual reality experience that involves placing the participant within a room like space that is surrounded by computer generated imagery. Modeling & Simulation Coordination Office
Chaotic System A system whose long-term behavior is unpredictable, tiny changes in the accuracy of the starting value can rapidly diverge to anywhere in its possible state space. There can, however, be a finite number of available states, so statistical prediction can still be useful. Modeling & Simulation Coordination Office
Commercial Off-The- Shelf (COTS) Commercial items that require no unique acquirer modifications or maintenance over the life cycle of the product to meet the needs of the procuring agency
Common Use Services, material, or facilities provided by an entity on a common basis within that entity or for two or more other entities, elements, or other organizations as directed.
Commonality A quality that applies to material, systems or environments: a. possessing like and interchangeable characteristics enabling each to be utilized, or operated and maintained, by personnel trained on the others without additional specialized training; b. having interchangeable modules, parts and/or components.
Component One of the parts that make up a system. (e.g. a hardware, software or control entity) IEEE 2008
Composability The capability to select and assemble reusable modeling and simulation components in various combinations into simulation systems to meet user requirements. Modeling & Simulation Coordination Office
Computational Model A model consisting of well-defined procedures that can be executed by a computer. (SISO-REF-002-1999) Modeling & Simulation Coordination Office
Computer Simulation A simulation that is executed on a computer, with some combination of executing code, control/display interface hardware, and, in some cases, interfaces to real-world equipment. Modeling & Simulation Coordination Office
Concept of Operations (ConOps) Describes the way the system works from the operator’s perspective. The ConOps includes the user description and summarizes the needs, goals, and characteristics of the system’s user community. This includes operation, maintenance, and support personnel. INCOSE
Concept Selection Rationale Documented demonstration of how (process) and why (results) the Concept Selection process arrived at the Recommended System Concept. ITS
Conceptual Data Model A model that documents the business information requirements and structural business process rules of the architecture, and describes the information that is associated with the information of the architecture. Included are information items, their attributes or characteristics, and their inter-relationships. Modeling & Simulation Coordination Office
Conceptual Model The description of what the model or simulation will represent, the assumptions limiting those representations, and other capabilities needed to satisfy the user’s requirements. A collection of assumptions, algorithms, relationships, and data that describe a developer’s concept about the simulation. Modeling & Simulation Coordination Office
Configuration A characteristic of a system element, or project artifact, describing their maturity or perfomance.
Configuration Management A discipline applying technical and administrative direction and surveillance to: identify and document the functional and physical characteristics of a configuration item, control changes to those characteristics, record and report change processing and implementation status, and verify compliance with specified requirements. ISO/IEC/IEEE 2010
Conservative Event Simulation A simulation in which events are processed in a manner that never violates the correct chronology. Modeling & Simulation Coordination Office
Constant A parameter, variable or data item within a model or simulation whose value cannot change during the course of the execution. Modeling & Simulation Coordination Office
Constrained Simulation A simulation where time advances are paced to have a specific relationship to wall clock time; real-time or scaled-real-time simulations (e.g., human-in-the-loop (e.g., training exercises), hardware-in-the-loop (e.g., test and evaluation simulations)). (SISO-REF-002-1999) Modeling & Simulation Coordination Office
Constraint An externally imposed limitation on a process, model, or dataset. (e.g., an equation (equality or inequality) that must be satisfied in order for a possible solution to be determined feasible.) Modeling & Simulation Coordination Office
Context Diagram A model of a function at the highest level of inputs, controls, outputs, and mechanisms GA Tech
Co-Simulation The different subsystems which form a coupled problem are modeled and simulated in a distributed manner