# Modelling

**Modelling**

**Modelling **(**^**)

Modelling is building Models for the representation of modules, i. e. the entities of a System.

__Stages__

Modelling requires one to:

- Decompose the system into its basic entities
- Identify the essential/relevant entities and linkages
- Recompose a simplified/selected version of the system with its essential/relevant entities and linkages (i.e. the model)

**Models ** (**^**)

**Models (^)**

__Definition__

A Model is a selected simplified representation of the essential or relevant entities (modules) of some specific reality and their characteristics (fields, factors, features).

__Classification__

The basic types of Models are:

- Iconic
- Analogue
- Symbolic

**Iconic (^)**

__Definition__

An Iconic Model is a look-alike representation of some specific entity (e.g. a house)

__Classification__

Iconic Models can be represented in:

- Two Dimensions : e.g. photos, drawings, etc.
- Three Dimensions : e.g. scale model

__Remark__

A scale model can be a:

- reduction (scaled down, e.g. the model of a building)
- reproduction (same scale, e.g. copy model, prototype or working model)
- enlargement (scaled up, e.g. the model of an atom)

of some specific entity

**Analogue (^)**

__Definition__

An Analogue Model is the representation of entities of a system by analogue entities pertaining to the model (e.g. through diagrams).

__Classification__

An Analogue Model can be built through:

- Two Dimensional Visualization : Charts, Graphs, Diagrams
(e.g. the colour coding of a geographical chart for representing different altitudes)

- Three Dimensional Visualization : Analogue Devices
(e.g. the flow of water in pipes to represent the flow of electricity in wires or the flow of resources in an economic system)

**Symbolic (^)**

__Definition__

A Symbolic Model is the representation of entities of a system through symbols.

Symbols can be:

- mathematical
- logical
- ad-hoc

__Remark__

A Symbolic Model is used whenever the reality is:

- too complex or too abstract to be portrayed through an iconic or analogue model
- the factors of the system (variables) can be represented by symbols that can be manipulated in a meaningful and fruitful way

**Modelling : summing up **(**^**)

Modelling is the building of Models.

Models can be:

- Iconic
- Analogue
- Symbolic

The use of Models allows for:

- Exploration
- Explanation
- Extrapolation

Extrapolation is achieved through manipulation of Models with a view to **Simulating**.