Glossary

0-D model

A model where no physical length is implied.

1-D model

A model which is defined in units of length.

2-D model

A model, which provides information either in the planar or radial sense.

3-D

Three-dimensional, refers to the visual display that exhibits width, height and thickness or depth.

3-D model

A model, which provides information in the 3 spatial dimensions.

6 DOF

Six degrees of freedom, refers to the number of simultaneous directions or inputs. Typically used to describe the combination of spatial positions (X, Y, Z) and orientation (roll, pitch, yaw).

Accessibility

The ease of approaching, entering, obtaining, or using.

Accuracy

1. The measure of the maximum deviation of an attribute or a parameter value in simulation from reality or some other chosen standard or referent.

2. The degree of conformity with a standard, or the degree of perfection attained in a measurement. Accuracy relates 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.

3. The degree of exactness of a model or simulation, high accuracy implying low error.

Accuracy/resolution

The smallest change in magnitude a sensor can detect.

Aggregation

1. The ability to group entities while preserving the collective effects of entity behavior and interaction while grouped.

2. Process of changing the resolution to represent items in a simulation in less detail.

Algebraic Loops

An algebraic loop occurs when a signal loop exists with only direct feedthrough within the loop. Direct feedthrough means that the output depends on the value of an input; the value of the input directly controls the value of the output. Non-direct-feedthrough components maintain a state variable. The term algebraic refers to equations that do not involve any derivatives. In Simcenter Amesim models, algebraic loops are algebraic constraints. Models with algebraic loops define a system of differential algebraic equations.

Analytical model

A model consisting of a set of solvable equations.

Animation

1. Used to experience a simulation in real-time (e.g., training simulations).

2. Graphics play-back and visualization are techniques that allow the analyst to see the behavior through time.

Application programming interface (API)

An API provides a set of documented functions and methods for interacting with a software product.

Application software

The application software represents the programs that are executed on a computer to perform tasks for the user such as simulation calculations.

Architecture

The structure of components in a program or system, their interrelationships, principles, and guidelines governing their design and evolution over time.

Assembly

A larger piece of a system's functionality assembled by reusing components as parts in an encompassing component or assembly of components, and wiring together their required and provided interfaces. Such assemblies are illustrated by means of component diagrams. In contrast, a component is an element of an assembly and doesn’t have any components, or sub-assemblies inside.

Attribute

A property or characteristic of one or more entities.

Authoring system

Any development tool suitable for developing a usable computer-based application.

Behavior

For a given object, how attribute value changes affect (or are affected by) the object attribute value changes of the same or other objects.

Behavioral model

Model of behavior for a component or supercomponent. In general, a component object can contain multiple behavioral models, describing the component at different levels of detail. Sometimes it is possible to capture this set of behavioral models in a single reconfigurable model. This requires, however, that all behavioral models have the same interface, a condition that may not always be satisfied. For instance, if we decided to model the thermal losses in a DC-motor, the interface would have to be expanded to include a thermal port.

Benchmark

An accepted representation or standard of a process being modeled or simulated against which the results of other models or simulations are compared or judged.

Benchmarking

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

Black box model

A model whose inputs, outputs, and functional performance are known, but whose internal implementation is unknown or irrelevant. Contrast with White 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.

CAD (Computer Aided Design)

CAD is the use of computer systems to aid in the creation, modification, analysis, or optimization of a design. CAD is mainly used for detailed engineering of 3D models and/or 2D drawings of physical components, but it is also used throughout the engineering process from conceptual design and layout of products, through strength and dynamic analysis of assemblies to definition of manufacturing methods of components. Computer-aided design is used in many fields. Its use in designing electronic systems is known as electronic design automation, or EDA. In mechanical design it is known as mechanical design automation (MDA) or computer-aided design (CAD), which includes the process of creating a technical drawing with the use of computer software.

CAE (Computer Aided Engineering)

CAE is the broad usage of computer software to aid in engineering analysis tasks. It includes Finite Element Analysis (FEA), Computational Fluid Dynamics (CFD), Multibody dynamics (MBD), Optimization, etc.

Calibration

The process of adjusting numerical or modeling parameters in the model to improve agreement with a referent.

Catalog

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

Circuit

A circuit diagram (also known as a circuit, a diagram, or a schematic) is a simplified conventional graphical representation of a circuit. A pictorial circuit diagram uses simple images of components, while a schematic diagram shows the components of the circuit as simplified standard symbols; both types show the connections between the devices, including power and signal connections. Arrangement of the components’ interconnections on the diagram does not correspond to their physical locations in the finished device.

Commercial off-the-shelf

A commercial off-the-shelf product is sold, leased, or licensed to the general public.

Commonality

A quality that applies to material/equipment or systems possessing like interchangeable characteristics enabling each to be utilized, or operated and maintained, by personnel trained on the others without additional specialized training.

Compilation

During model compilation, a model compiler converts the model to an executable form, a process called compilation.

Compliance tests

Tests conducted to evaluate the consistency and correctness of Protocol Data Unit (PDU) interpretation and utilization by a simulation.

Component

A subset of the physical realization of the system. A component object is the combination of a configuration interface (list of ports), a graphical form (icon) and behavior model(s). A component object can contain multiple behavioral models, describing the component at different levels of details. Multiple component objects can be organized into libraries.

Component alias

Once a component icon instance is created, it can be assigned an alias. An alias is a user unique identifier for a component at a given level.

Component alias path

Alias path identifies one and only one component in the entire system sketch. It is the concatenation of all the component aliases from the higher level (sketch level) to the lower level (supercomponent level N) separated by . (dot): alias_0.alias_1.alias_i.alias_N.

Component icon

In Simcenter Amesim, it is the combination of a configuration interface (list of ports) and a graphical form (icon).

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.

Conceptual model

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

Conditional event

A sequentially dependent event that will occur only if some other event has already taken place. See Time-dependent event.

Configuration

A collection of products' descriptive and governing characteristics. These can be expressed in (a) functional terms such as what performance the product is expected to achieve and (b) in physical terms such as what the product should look like and consist of when completed.

Configuration management

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.

Connection

Connections refer to port or connector point to an element (model component), at which a connection to other elements can take place. Only connectors of the same type can be together.

Connection line

Physical connection lines have no inherent directionality and represent the exchange of energy flows. You can connect conserving ports only to other conserving ports of the same type. The Physical connection lines that connect conserving ports together are non-directional lines that carry physical variables rather than signals.

Consistency

Data maintained so that it is free from variation or contradiction.

Contextual menu

A context menu (also called contextual, shortcut, and popup or pop-up menu) is a menu in a graphical user interface (GUI) that appears upon user interaction, such as a right-click mouse operation.

Contextual window

Windows devoted to providing information and describing properties. In Simcenter Amesim, it often refers to the Parameters window and the Variables window.

Continuous model

A computational model whose output variables change in a continuous simulation. Contrast with Discrete simulation.

Continuous system

A system for which the state variables change continuously with respect to time.

Customization

Also called Personalization. Consists of tailoring a product to accommodate specific individuals, sometimes tied to groups or segments of individuals. Customization is used to improve customer satisfaction.

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.

Data

Representation of facts, concepts, or instructions in a formalized manner suitable for processing by humans or by automatic means.

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 integrity

The condition in which data is accurate, current, consistent, and complete.

Data path

Identifies a variable or a parameter in a system. It uses the varname and the alias path. Note you can get the data path of a parameter or a variable from the contextual view. For a global parameter, the data path is the global parameter varname.

Data quality

The correctness, timeliness, accuracy, completeness, relevance, and accessibility that make data appropriate for use.

Data validation

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

Dependent variable

A variable whose value is dependent on the values of one or more independent variables. Contrast with Independent variable.

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. Contrast with Stochastic model.

Deterministic system

A system in which the new state of the system is completely determined by the previous state and by activity.

Diagram

Depicts how components are wired together to form larger components or whole systems. Diagrams are used to illustrate the structure of arbitrarily complex systems. In the sketch (diagram view), the structure of a model is composed, edited, and displayed using element symbols and connecting lines.

Digital simulation

A simulation that is designed to be executed on a digital computer system.

Disaggregate

Activity that decomposes an aggregated entity into multiple entities representing its components. Contrast with Aggregate.

Discontinuity

1. Event affecting the evolution of a dynamic system. Physical examples of discontinuities are: end-stop, backlash, frictional stick-slip, any form of dead band, hysteresis, a valve such as a check valve that has characteristics when open which are completely different to when closed, linear interpolation of tabulated data, ...

2. A point at which the relationship between the independent variable and the dependent variable changes; i.e., the point where a function is not mathematically continuous.

Discrete event simulation

A simulation that uses a discrete model where the dependent variables (i.e., state indicators) change discretely at points in time referred to as events. Contrast with Continuous simulation.

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. Contrast with Continuous model.

Discrete system

A system for which the state variables change instantaneously at separate points in time referred to as events.

Discretization

The process of dividing a continuous system into a finite number of elements with finite size. The difference between the discretized representation and the real system, the discretization error, drops as the size of the elements decrease. For a time-dependent analysis, a discretization of time into steps provides an idealized behavior of the variations in the solution during these steps.

Distributed element

A model that assumes that the attributes of the system (resistance, capacitance, and inductance) are distributed continuously throughout the system. The distributed model is used at high frequencies where the wavelength approaches the physical dimensions of the system, making the lumped model inaccurate.

Docked window

A window that appears at a fixed location on the edge of its owner window.

Domain

The physical or abstract space in which the entities and processes operate. The domain can be an abstract domain, such as an n-dimensional mathematics space, or economic or psychological domains. A (physical) domain in Simcenter Amesim is the overall set of ports, physical dimensions, units, properties, ... which belong to one physical discipline (mechanics, hydraulics, pneumatics, thermal, etc.).

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.

Dynamic simulation model

Systems whose response to an input is not instantaneously proportional to that input or disturbance and whose behavior can be characterized by either an n-th order differential equation, a transfer function, or a set of n simultaneous differential equations.

Encapsulation

The process of hiding the details of an object that do not contribute to its essential characteristics.

Encryption

Process of encoding information in such a way that only authorized parties can read it.

Environment

The texture or detail of the natural domain and the external objects, conditions, and processes that influence the behavior of a system.

Equation

An equation formulates physical laws and dependencies for a behavioral model. Equations usually contain several state and result variables. In order to compute the unknown quantities, the set of equations is solved by solver(s).

Equilibrium

State of a model where the time derivatives of all state variables are zero. In mechanics, it’s often called "static equilibrium" while in thermodynamics it’s often called "steady-state equilibrium". A system can have one equilibrium, several equilibria, or also no equilibrium. See Steady state.

Event

A change of object attribute value, or an interaction between objects 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.

Executable model

A model that runs, i.e., it implements a conceptual model in a form (presumably computer compatible) that can be used for some purpose.

Exportable

Ease with which objects, data or components can be moved from one domain or event and used in another.

Extensibility

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

Fidelity

1. The identification of key parameters for a system and the degree to which the aggregate of those parameters match a baseline system. The components of fidelity include functional, physical, psychological, tactile, visual, and wallpaper.

2. The degree to which the representation within a simulation is similar to a real-world object, feature, or condition in a measurable or perceived manner.

3. The accuracy of the representation when compared to the real world.

Final condition

The values assumed by the variables in a system, model, or simulation at the completion of some specified duration of time. Contrast with Boundary condition, Initial condition.

Final state

The values assumed by the state variables of a system, component, or simulation at the completion of some specified duration of time. Contrast with Initial state.

Fixed-step solvers

1. Solve the model at regular time intervals from the beginning to the end of the simulation. The size of the interval is known as the step size. You can specify the step size. Generally, decreasing the step size increases the accuracy of the results while increasing the time required to simulate the system.

Flexible

Adaptable or variable. Able to change components created for a specific case to be useful in another case.

Framework

A software framework is a universal, reusable software environment that provides particular functionality as part of a larger software platform to facilitate development of software applications, products and solutions. Software frameworks may include support programs, compilers, code libraries, tool sets, and application programming interfaces (APIs) that bring together all the different components to enable development of a project or solution.

Frequency domain

Domain for analysis of functions or signals with respect to frequency, rather than time.

Functionality

Set of functions required to produce a particular output.

Generic 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.

Global parameters

A global parameter is a parameter with a global scope, meaning it’s accessible throughout the whole system. Global parameters are used extensively to pass parameter values between different parts of the models.

Graphical user interface

A computer environment or program that displays, or facilitates the display of, on-screen options, usually in the form of icons (pictorial symbols) or menus (lists of alphanumeric characters) by means of which users may enter commands.

GTAC

Global Technical Access Center, the product support help desk for Siemens PLM products.

Host computer

A computer that supports one or more simulation applications. All host computers participating in a simulation are connected by network(s).

I/O

Input/Output.

Infrastructure

An underlying base or foundation; the basic facilities, equipment, and installations needed for the functioning of a system.

Initial condition

The values assumed by the variables in a system, model, or simulation at the beginning of some specified duration of time. Contrast with Boundary condition, Final condition.

Initial state

The values assumed by the state variables of a system, component, or simulation at the beginning of some specified duration of time. Contrast with Final state.

Instantiation

To represent an abstraction by a concrete instance (e.g., in object oriented programming the creation of a new object (or instance) of a class is called instantiation. Instantiation allows for example the definition of components and submodels.

Interface

All the ports combined are the interface of the model. This interface defines how the component can interact with the other components in the system, but does not contain any information about the internal behavior of the component.

Interoperability

1. Interactions between two or more systems affected by allowing information to be exchanged and used by the receiving system. There is an implied level common understanding that is shared between sender and receiver.

2. The capability, promoted but not guaranteed by joint conformance with a given set of standards, that enables heterogeneous tools, generally built by various vendors, to work together in a network environment.

3. Interoperability exists when different systems exhibit the "same" behavior (performance) when stimulated by a set of standard procedures. The term "same", above, should be framed for a given task or class, be within a specified tolerance or number of anomalies, and with a predefined number of statistically measurable trials.

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.

Legacy system or code

The term "legacy system" or "legacy code" usually refers to computer systems or programs of an outdated technology level designed in the past, but still in use because of complications and costs of migrating to state-of-the-art systems.

Library

The component objects are organized in a hierarchical component library. From this library, the user selects the components that achieve the desired functionality within the system.

Library tree

The Library tree is used to browse and search Simcenter Amesim libraries for components to use in the models. Users can also select from a list of "Favorites" library components (shortcuts to standard library components).

Linearization

Process to linearize a non-linear system around an operating point. A linear system equivalent to the non-linear system around its operating point is obtained as output of the linearization process. The linearization can be a numerical linearization with small perturbations applied to the system around the operating point (such as in Simcenter Amesim) or a formal linearization with the derivation of the analytical non-linear equations (most of the time, to be done manually, which is quite fastidious).

Live simulation

Live simulation involves real people operating real systems.

Locked-variable model

A model in which some of the variables are held constant and the others are allowed to vary.

Lookup Table

A lookup table provides data to map input values to output values, approximating with interpolation/extrapolation mathematical functions. Given input values, a lookup operation is performed to retrieve the corresponding output values from the table. If the lookup table does not define the input values, the lookup table estimates the output values.

Lumped Parameter Model

The lumped element model (also called lumped parameter model, or lumped component model) simplifies the description of the behavior of spatially distributed physical systems into a topology consisting of discrete entities that approximate the behavior of the distributed system under certain assumptions. Mathematically speaking, the simplification reduces the state space of the system to a finite number, and the partial differential equations (PDEs) of the continuous (infinite-dimensional) time and space model of the physical system into ordinary differential equations (ODEs) with a finite number of parameters.

Mathematical model

A mathematical model is a symbolic model whose properties are expressed in mathematical symbols and relationships. Mathematical models are commonly used to quantify results, solve problems and predict behavior.

Measure of effectiveness

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 performance

Measure of how the system performs its functions in a given environment (task completion time, ...). It is closely related to inherent parameters (physical and structural) but measures attributes of system behavior. See Measure of effectiveness.

Mechatronics

Design process that includes a combination of mechanical engineering, electrical engineering, control engineering and computer engineering. Mechatronics is a multidisciplinary field of engineering. It includes control systems as well as numerical methods used to design products with built-in intelligence.

Metadata

Searchable information describing the characteristics of data; data or information about data; or descriptive information about an object’s data, data activities, systems, and holdings. For example, metadata for a model or simulation will include keywords and/or a description of the capabilities along with developer and user information.

Metamodel

A model of a model. Metamodels are abstractions that use functional decomposition to show relationships, paths of data and algorithms, ordering, and interactions between model components and subcomponents.

Methodology

The system of principles, practices, and procedures, applied to a specific branch of knowledge.

Middleware

Software that connects or integrates other software modules or components, typically providing a set of communications or interaction functions that may be invoked by the linked modules.

MIMO

Multi-Input, Multi-Output (MIMO) models. Users can define for example MIMO Transfer Function Model, MIMO State-Space Model, or MIMO Frequency Response Data Model.

Model

A physical, mathematical, or otherwise logical representation of a system. We can find for example structural models or analytical models.

Model Based Design (MBD)

Mathematical and visual method of addressing problems associated with designing complex control systems. It is used in many motion control, industrial equipment, aerospace, and automotive applications. It's a process that enables faster, more cost-effective development of dynamic systems, including control systems, signal processing, and communications systems. In Model-Based Design, a system model is at the center of the development process, from requirements development, through design, implementation, and testing. The model is an executable specification that you continually refine throughout the development process. After model development, simulation shows whether the model works correctly.

Model Based System Engineering (MBSE)

A systems engineering methodology which focuses on creating and exploiting domain models as the primary means of information exchange between engineers, rather than on document-based information exchange. More recently, the focus has also started to cover aspects related to the model execution in computer simulation experiments, to further overcome the gap between the system model specification and the respective simulation software.

Model Explorer

Structured display and access for the properties of components and connections in a model. The tree structured view shows the components and the hierarchy of the model with its supercomponent levels. It’s similar to the sketch view of the model, except it’s presented in a tree view for a quick access and efficient operations compared to multi-selections from the sketch view.

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

The discipline that comprises the development and/or use of models and simulations.

Model Order Reduction

Some modern models of real-life systems pose challenges when used in numerical simulations, due to complexity and large size (dimension). Model Order Reduction aims to lower the computational complexity of such problems, for example, in simulations of large-scale dynamical systems and control systems. By a reduction of the model's associated state space dimension or degrees of freedom, an approximation to the original model is computed. This reduced order model (ROM) can then be evaluated with lower accuracy but in significantly less time.

Multidisciplinary

Work by combining several disciplines or methods. A multidisciplinary community or project is made up of people from different disciplines and professions who are engaged in working together as equal stakeholders in addressing a common challenge.

Multidisciplinary models

Multidisciplinary models combine various modeling techniques such as dynamic simulation in different areas like automatic control and signal processing.

Multiphysics

Multiphysics models include more than one equation and variable from different types of physics. These variables can be defined in different domains.

Multi-step methods

Used for the numerical solving of ordinary differential equations. Conceptually, a numerical method starts from an initial point and then takes a short step forward in time to find the next solution point. Multistep methods attempt to gain efficiency by keeping and using the information from previous steps rather than discarding it. Consequently, multistep methods refer to several previous points and derivative values.

Network

An arrangement of nodes and interconnecting branches.

Non-Linearity

Real systems have all kinds of non-linearities: dead-band, backlash, Coulomb friction, hysteresis, quantization, saturation, kinematic non-linearities, and many others.

Numerical stability

The property of a numerical process to behave in an orderly manner.

Occurrence

Number of a specific instance of specific component within an assembly. Occurrences have position, quantity and info that are specific to a particular instance of a component within a particular assembly.

Openness

There are three perspectives on open systems:

1. Portability: the degree to which a system component can be used in various environments,

2. Interoperability: the ability of individual components to exchange information, and

3. Integration: the consistency of the various human-machine interfaces between an individual and all hardware and software in the system.

Operating point

The thermodynamic and flow or engine operating conditions like pressure, temperature, flow-rate, rotational speed, ...

Parameter

Quantitative properties of a submodel, supercomponent or model. The value (constant, expression or global parameter) of the parameter is entered using the user interface or set externally via scripting capabilities.

Persistent

Enduring availability for re-use of components after the completion of a specific case.

Physical architecture

The identification and arrangement of the physical components of a system into an orderly framework that describes the physical structure, the technical functions, design features and technical attributes that can be achieved by each component and by the system within specified constraints.

Physics-based modeling

Physical models in which the equations that constitute the model are those used in physics to describe or define physical phenomena being modeled.

Platform

Essential collections of software parts that manage resources and provide common services for other software parts that run "on top" of them. The platform provides functionalities needed by users for running various applications, as well as several features to support the different cases encountered by users. Typically a graphical user interface which allows a user to interact with the software and its associated features.

Plugin

A software component that adds a specific feature to an existing computer program. When a program supports plug-ins, it enables customization. The host application provides services which the plug-in can use, including a way for plug-ins to register themselves with the host application and a protocol for the exchange of data with plug-ins. Plug-ins depend on the services provided by the host application and do not usually work by themselves. Conversely, the host application operates independently of the plug-ins, making it possible for end-users to add and update plug-ins dynamically without needing to make changes to the host application.

Port

Also called physical port. A port defines an intended interaction between a component and its environment. Ports correspond to points where a component exchanges power or signals with the environment. There is one for each separate interaction point and the type of a port matches the type of power exchange. For example, a DC motor could have four ports, two electrical and two mechanical. The electrical ports correspond to the electrical connectors of the motor, the mechanical ports to the stator and the rotor.

Port dimension

It specifies the dimensions that a variable must have in order to be connected to another component.

Port name

Name of the port that can be added to Supercomponents to be visible in labels.

Port number

Specifies the port number of the component. In Simcenter Amesim, port numbers are automatically defined starting from the left bottom corner and increasing anti-clock wise.

Port tag

Identifier for remote ports used for Transmitters/Receivers.

Precision

The quality of the operation by which the result is obtained and can be repeated.

Predictive model

A model in which the values of future states can be predicted.

Proprietary

A technological design or architecture whose configuration is unavailable to the public and may not be duplicated without permission from the designer or architect.

Quality assurance

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.

Quasi-static process

A thermodynamic process that happens infinitely slowly. It is important to note that no real process is quasi-static. Therefore in practice, such processes can only be approximated by performing them infinitesimally slowly. A quasi-static process ensures that the system will go through a sequence of states that are infinitesimally close to equilibrium (so the system remains in quasi-static equilibrium), in which case the process is typically reversible.

Regression testing

Retesting a portion of the system after a change has been made to ensure that new problems were not introduced.

Reliability model

A model used to estimate, measure, or predict the reliability of a system.

Repeatability

Ability to accurately recreate responses under identical stimuli.

Resolution

The degree of detail and precision used in the representation of real world aspects in a model or simulation.

Result variable

Variable of a submodel, supercomponent or model computed all along the simulation run.

Reusability

The degree to which a software module or other work product can be used in more than one computing program or software system.

Reuse

The practice of using again, in whole or part, existing tools, data, or services. Reuse encompasses the policy, practices, and the supporting technology that foster the effective reuse of resources to include requirements, conceptual models, software architecture, designs, algorithms, software components, models, simulations, and data.

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.

Scenario

An initial set of conditions and timeline of significant events imposed on systems to achieve objectives.

Sensitivity

The sensitivity measures how much change is caused in the output by small changes to the reference input or parameters. Sensitive systems have very large changes in output in response to small changes in the input or parameters.

Sensitivity Analysis

The study of how the variation in the output of a model can be apportioned to different sources of variation in the model input and parameters.

Signal

In addition to physical ports and connection lines that model power/energy flow, we also consider signal ports and signal connection lines. There’s no power/energy flow through signal ports, and the connections between them are directed.

Simulated time

Time as represented within a simulation.

Simulation

A method for implementing a model over time. The evolution of the behavioral model in time is computed during the simulation run. This depends on the model itself as well as the parameters and initial values used. As a result, the user gets the evolution in time of all result variables.

Simulation application

The executing software on a host computer that models all or part of the representation of one or more simulation entities.

Simulator

A device, computer program, or system that performs simulation.

Simulator entity

Computational device for generating behavior of the model.

SISO

Single-Input, Single-Output (SISO) models.

Sketch

Generally speaking, a sketch is a rapidly executed freehand drawing that is not usually intended as a finished work. A sketch may serve a number of purposes like a quick way of graphically demonstrating an idea. In Simcenter Amesim, the Sketch mode is the first mode to start creating the model.

Solvers

A dynamic system is simulated by computing its states at successive time steps over a specified time span, using information provided by the model. The process of computing the successive states of a system from its model is known as solving the model. No single method of solving a model suffices for all systems. Accordingly, a set of programs, known as solvers, are provided that each embody a particular approach to solving a model.

Stability

The quality or state of something that is not easily changed or likely to change.

Standard libraries

Physical and applicative libraries provided off-the-shelf in Simcenter Amesim. In contrast, user-defined libraries are developed/validated/maintained by users themselves.

States

The values assumed at a given instant by the variables that define the characteristics of a system, component, or simulation. Synonym: System state. See 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.

Static simulation model

Representation of a system at a particular time, or one that may be used to represent a system in which time simply plays no role.

Static variables

Variables that do not change over the course of an experiment.

Stationary model

A model where the dependent variables do not change over time. It typically represents a steady-state solution. Also called static model or steady model.

Steady state

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

Stimulate

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

Stimulation

The use of simulations to provide an external stimulus to a real system or subsystem.

Submodel

A behavioral model associated with a component. Submodels can be based upon equations and representations of varying complexity. Additionally, they can have varying numbers of inputs, outputs and parameters, depending on the behavioral model which they are based on.

Subsystem

A subsystem is a set of components as a sub-part of the whole system. As the system increases in size and complexity, users can simplify it by grouping components into subsystems. Using subsystems has these advantages: it helps reduce the number of components displayed in your model sketch, it keeps functionally related components together, it establishes a hierarchical sketch, where a subsystem is on one layer and the components that make up the subsystem are on another.

Supercomponent

A supercomponent can be hierarchically defined when it consists of a composition of components, resulting in a compound component. When these components are also compound (i.e. supercomponents), multiple levels of hierarchy occur. The bottom of the hierarchy consists of the primitive components with their submodels that are defined only by their constitutive equations.

System

A collection of components organized to accomplish a specific function or set of functions.

System architecture

A representation of a system in which there is a mapping of functionality onto software components, and human interaction with these components.

System dynamics

An approach to understanding the behavior of complex systems over time. The basis of the method is the recognition that the structure of any system is often just as important in determining its behavior as the individual components themselves.

System model

A representation of a real system.

Systems Engineering

Systems engineering is an interdisciplinary field of engineering that focuses on how to design and manage complex engineering systems over their life cycles. Issues such as requirements engineering, reliability, logistics, coordination of different teams, testing and evaluation, maintainability and many other disciplines necessary for successful system development, design, implementation, and ultimate decommission become more difficult when dealing with large or complex projects. Systems engineering deals with work-processes, optimization methods, and risk management tools in such projects. It overlaps technical and human-centered disciplines such as control engineering, industrial engineering, software engineering, organizational studies, and project management. Systems engineering ensures that all likely aspects of a project or system are considered, and integrated into a whole.

System Simulation

A set of techniques that use computers to imitate the operations of real-world systems through simulation. Computers are used to generate numerical models for the purpose of describing or displaying complex interactions among multiple variables within a system.

System state

The collection of state variables necessary to describe the system at a particular time.

Tabular model

A symbolic model whose properties are expressed in tabular form; for example, a truth table that represents a Boolean logic "OR" function.

Technical data

Scientific or technical information recorded in any form or medium (e.g., manuals and drawings). Computer programs, related software, financial data and other information related to contract administration are not technical data while documentation of computer programs and related software are.

Test and Evaluation

The act of generating empirical data during the research, development or sustainment of systems, and the creation of information through analysis that is useful to technical personnel and decision makers for reducing design and acquisition risks. The process by which systems are measured against requirements and specifications, and the results analyzed so as to gauge progress and provide feedback.

Time

The measurable aspect of duration.

Time-dependent event

An event that occurs at a predetermined point in time or after a predetermined period of time has elapsed. See Conditional event.

Time domain

Analysis of physical systems with respect to time. In the time domain, the signal or function's value is known for all real instants for the case of continuous time, or at various separate instants in the case of discrete time.

Time variable

A variable whose value represents simulated time.

Tolerance

1. The Relative tolerance measures the error relative to the size of each state. The relative tolerance represents a percentage of the state value.

2. Absolute tolerance is a threshold error value. This tolerance represents the acceptable error as the value of the measured state approaches zero.

Tool

Software that implements a model or simulation.

Transient

Unsteady state.

Transient model

A model where at least one of the dependent variables changes over time. Also called dynamic model, time-dependent model, or unsteady model.

Transmitter/Receiver

Transmitter and Receiver components allow users to pass variables from one component to another without actually connecting them. The Transmitter component passes its input to its corresponding Receiver components. The Receiver components accept variables from a corresponding Transmitter component, then pass them as outputs. To associate a Transmitter component with a Receiver component, enter the Port tag list.

Unit conversion

A system of converting measurement from one basis to another.

Unsteady

Description of a system which is time-varying.

Usability

Usability is the degree to which a software can be used by specified consumers to achieve quantified objectives with effectiveness and satisfaction in a quantified context of use. Practically it covers a combination of attributes like accessibility, ergonomics, learnability, efficiency, documentation & help.

User-defined library

Also called custom library. Library that is specially developed for some specific organization or other user. As such, it can be contrasted with the use of software packages for standard libraries developed for the mass market, such as commercial off-the-shelf (COTS) libraries.

User experience

User experience (UX) refers to a person's emotions and attitudes about using a particular product. User experience includes the practical, experiential, affective, meaningful and valuable aspects of human–computer interaction and product ownership. User experience is dynamic as it is constantly modified over time due to changing usage circumstances and changes to individual systems as well as the wider usage context in which they can be found.

Utilities

Auxiliary software programs that provide additional capabilities to application programs or the operating system.

Validation

The process of determining the degree to which a model or simulation and its associated data are an accurate representation of the real world from the perspective of the intended uses of the model.

Validity

1. 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 for a specific use.

2. The quality of being calculated correctly enough to suit a specific application.

Variable

A quantity or data item whose value can change. See Dependent variable, Independent variable, State variable. Contrast with Constant.

Variable-step solvers

Step size is variable during the simulation. Variable-step solvers reduce the step size to increase accuracy when a model's states are changing rapidly and increasing the step size to avoid taking unnecessary steps when the model's states are changing slowly.

Variant

1. Variants are multiple implementations for a submodel or a supercomponent.

2. A variant is a specialization of a model and inherits all of its properties, unless they are defined locally. This allows a very compact modeling of models that vary only in a few properties.

Varname

Identifies a variable or a parameter in a submodel. Note for a global parameter, it identifies the parameter in the whole system.

Verification

The process of determining that a model or simulation implementation accurately represents the developer's conceptual description and specification.

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 simulation

A simulation involving real people operating simulated systems.

White box model

A model whose internal implementation is known and fully visible. Synonym:  Glass box model. Contrast with Black box model.

Wizard

A sequence of pages that guides users through a multi-step, infrequently performed task. Effective wizards reduce the knowledge required to perform the task compared to alternative UIs.