3.1 Introduction

System modelling supports the analysis and design process by introducing a degree of formality into the way systems are defined. During system development it is often the case that pictures are used to help visualize some aspects of the development. Modelling provides a way of formalizing these representations, through diagrams, by not only defining a standard syntax, but also providing a medium for understanding and communicating the ideas associated with system development.

The art of modelling is arguably the most creative aspect of the work of the systems engineer. There is no "right" solution and models will evolve through various stages of system development. Models are most often represented visually and the information is therefore represented through connected diagrams. New methods such as object orientation have advanced the concept of modelling; however, most approaches are also based on the principles used and tested over time.

A good model is one which is easily communicated. They need to be used for communication within a development team, and also to an organization as a whole, including the stakeholders. The uses of a model can be diverse and cover a wide spectrum. It might be to model the activities of an entire organization or to model a specific functional requirement of a system.

Modelling has the following benefits:

• Encourages the use of a precisely defined vocabulary consistent across the system.

• Allows system specification and design to be