Definitions

• Modelling: The process of creating and constructing a model that represents a real or proposed system, including its properties and working principles. It is described as “an act of building a model” to help analysts predict the effect of changes to the system.
• Simulation: The operation of a model over time or space to study the performance of a system. It is defined as “an act of using a model for simulation” to analyze the performance of an existing or proposed system.

Core Terminology

• Object: An entity existing in the real world whose behavior is studied.
• System: An articulate object under definite, real-world conditions.
• Base Model: A hypothetical explanation of an object’s properties and behavior that is considered valid across the model.
• Experimental Frame: The context used to study a system, including experimental conditions, objectives, and specific aspects of interest. It comprises Frame Input Variables and Frame Output Variables.
• Lumped Model: An exact explanation of a system that follows the specific conditions of a given Experimental Frame.
• Verification: The process of comparing a simulation program’s consistency with a lumped model to ensure accurate performance. It involves comparing two or more items to ensure accuracy.
• Validation: The process of comparing simulation results with experimental measurements from the real system within the context of an Experimental Frame. A mismatch indicates the model is invalid.

System State Variables

System state variables are a set of data required to define the internal processes within a system at a given point in time.

• Entities & Attributes: An entity represents a static or dynamic object. Attributes are the local values used by an entity.
• Resources: An entity that provides a service to one or more dynamic entities. A dynamic entity can request, use, and release resources.
• Lists: Used to represent queues for entities and resources, which can operate under various principles such as LIFO (Last-In, First-Out) or FIFO (First-In, First-Out).
• Delay: An indefinite duration of time caused by a combination of system conditions.