Modeling and Simulation

Simulation Modeling and Analysis

The process of creating and experimenting with a computerized mathematical model of a physical system.

Model

A representation of a real system which helps the analyst predict the effect of changes to the system.

Modeling

The process of creating a model which represents a system including its properties.

Simulation

The operation of a model in terms of time or space which helps analyse the performance of a system.

Discrete System

A system where state changes occur at discrete points in time when events occur.

Continuous System

A system where the status of some component is continuously changing with respect to time.

Stochastic System

A system that is affected by randomness, making its output unpredictable.

Deterministic System

A system that is not affected by randomness, making its output predictable.

Entity

An object or person that moves through a system and changes its state.

Queue

The simulation term for a line where entities wait to be processed.

Resource

A component that processes or serves the entities in a queue.

System Time

The total amount of time that an entity spends in the system.

Queue Time

The total amount of time that an entity spends waiting in a queue.

Utilization

A time-dependent statistic measuring the proportion of time a resource is busy.

Process

A series of steps and decisions in the way work is completed.

Event

An instantaneous happening that changes the state of the system.

FIFO (First-In, First-Out)

A queue priority rule where the first entity to enter the queue is the first to be served.

Balking

A queue behavior where an entity arrives but leaves before entering the queue.

Reneging

A queue behavior where an entity enters the queue but leaves before being served.

Jockeying

A queue behavior where an entity switches between parallel queues.

Problem Statement

A clear description of an issue, including a vision and method to solve it.

Work Breakdown Structure (WBS)

A project planning tool involving the successive division of project tasks into subtasks.

Gantt Chart

A horizontal bar chart used to illustrate the duration and sequence of project tasks.

Verification

The process of ensuring that the simulation model operates as intended and is free of programming errors.

Validation

The process of ensuring that the simulation model represents reality at a given confidence level.

Face Validity

A validation process where domain experts ensure the model, on the surface, represents reality.

Statistical Validity

A validation process involving a quantitative comparison of the model's output with data from the real system.

Factor

A controllable variable in an experiment that affects the system's output performance.

Level

The specific value or setting of a factor in an experimental design.

Replication

A single complete run of a simulation model from its initial state to its ending state.

Terminating Simulation

A simulation that starts and ends at a defined state or time.

Nonterminating Simulation

A steady-state simulation that runs to analyze the long-term behavior of a system.

Steady State

The condition of a nonterminating system where its behavior has become balanced and representative.

Autocorrelation

The correlation between successive observations of output performance in a simulation run.

Executive Summary

A condensed section of a report summarizing project objectives, results, and recommendations for a non

Model

According to Shannon, this is a representation of an object, a system, or an idea in some form other than that of the entity itself.

Model

This is similar to but simpler than the system it represents.

Model

This should be a close approximation to the real system and incorporate most of its salient features.

Simulation

A technique or set of techniques whereby, the development of models helps one to understand the behavior of a system, real or hypothetical.

Simulation Model

The behavior of a system that evolves over time is studied by developing a ______.

Problem Formulation

A step in simulation study that covers the "statement of the problem."

Set Objectives and Project Plan

A step in simulation study that covers the "allocation of resources (people, cost, time, etc.)"

Model Conceptualization

A step in simulation study that "requires experience," "begins simple and then add complexity," and "captures the essence of the system."

Data Collection

A step in simulation study that is "time consuming and must begin early."

Model Translation

A step in simulation study that is in "computer form."

Verification

A step in simulation study that asks "does the program represent model and run properly?"

Validated

A step in simulation study that asks "does the model replicate the system?"

Experimental Design

A step in simulation study that covers the "times, initializations, etc."

Production and Analysis

A step in simulation study that covers the "actual runs and analysis of results that determine performance measures."

Documentation and Reporting

A step in simulation study that covers the "progress reports are important as project continues like history, chronology, changes, etc."

Implementation

The last and crucial step of simulation study

Failure to define an achievable goal

One of the Ten Reasons of Failure

Incomplete mix of essential skills (Project leadership, Modeling, Programming, and Knowledge of modeled system)

One of the Ten Reasons of Failure

Inadequate level of user participation

One of the Ten Reasons of Failure

Inappropriate level of detail

One of the Ten Reasons of Failure

Poor communication

One of the Ten Reasons of Failure

1960s

Simulation started unknowingly since the ____’s in Lunar Expedition Studies.

Monte Carlo Simulation

A simulation technique that uses random sampling and statistical modeling to estimate the probability of outcomes in a process that is too complex for analytical solutions.
Jon Von Neumann

Analog and Digital

Fields of Computing in Post

Gordon Simulator

A simulation tool presented by IBM to Norden in October 1961, developed by Geoffrey Gordon.
Transaction (Process) Based Orientation

CSL (Control and Simulation Language)

In England, J. Buxton and J. Laski developed _____.

SIMULA

An early simulation programming language developed in Norway by O. Dahl and K. Nygaard.

SOL (Simulation Oriented Language)

A symbolic language for general purpose system simulation developed by Don Knuth and J. McNeley.

The Art of Simulation

A short book on simulation methodology written by Ken Tocker.

SLAM (Simulation Language for Alternative Modeling)

In 1979, Alan Pritsker and David Pegden created _____.

SIMAN (SIMulation ANalysis)

A simulation language developed by Dennis Pegden around 1983, designed to run on a PC and tailored for the PC market.

CINEMA

An animation package introduced for the SIMAN language around 1985, originally an add

A simulation is not appropriate/needed...

when it is easier to perform direct experimentation.

A simulation is not appropriate/needed...

when the cost exceeds savings.

A simulation is not appropriate/needed...

when the behavior of the system is too complex to define.

System

A _____ can contain subsystems which themselves are _____.

System

An object or collection of objects whose properties we want to study.

System

Defined to be a collection of entities, e.g., people or machines, that act and interact together toward the accomplishment of some logical end.

Discrete System

A type of system in which the state variables change only at a discrete set of points in time.

Continuous System

A type of system in which the state variables change continuously over time.

Engineering Point of View in System Study

"Study a system to understand it in order to build it."

Natural Science Point of View in System Study

"Satisfy human curiosity, e.g. to understand more about nature."

Natural and Artificial Systems

Two Classifications of Systems

Natural Systems

A classification of system that are part of nature or not man

Artificial Systems

A classification of system that is manufactured by man.

Observable

An important property of a system that says, "it should be _____."

Entity

An object of interest in the system (ex. machines in factory)

Attribute

The property of an entity (ex. speed and capacity)

Activity

A time period of specified length (ex. welding and stamping)

State

A collection of variables that describe the system in any time (ex. status of a machine (busy, idle, down, etc.))

Event

An instantaneous occurrence that might change the state of the system (ex. breakdown)

Endogenous

Activities and events occurring with the system.

Exogenous

Activities and events occurring with the environment.

Inputs

A component of the system which are also variables of the environment that influence the behavior of the system.

Outputs

A component of the system which are also variables that are determined by the system and may influence the surrounding environment.

Classification of Models

Conceptual/Physical, Abstract/Mathematical, Simulation, and Heterogeneous Models

Conceptual/Physical Models

Also known as replica models. It is a physical object that mimics some properties of a real system, to help us answer questions about that system.

Abstract/Mathematical Models

Also known as abstract models. It considers mathematical notions as an abstraction of the reality it is meant to portray.

Simulation Models

This classification of model includes computer simulation, actual experiments and model validation.

Heterogeneous Models

This classification of model is also known as combined models of all class of models.

Continuous Time Models

Models evolve their variable values continuously over time.

Discrete Time Models

Models may change their variable values only at discrete points in time.

Static Models

This is a model that can be defined without involving time, where the word _____ is derived from the Greek word statikos, meaning something that creates equilibrium. They are often used to describe systems in steady

Dynamic Models

model includes time in the model. The word _____ is derived from the Greek word dynamis meaning force and power, with _____ being the (time

Resistor

A static system where the voltage is directly proportional to the current, independent of time, whereas a capacitor is a dynamic system where voltage is dependent on the previous time history.