
Students Guide to Information
Technology
Let's now look in detail at the modelling tools needed to build
the essential model. I'll take them in the order listed in the previous
section. As stated there, the first three (the description of the
system's purpose, the context diagram, and the event list) make up
the environmental part of the model, and the last five make up the
behavioural part.
The statement of purpose
Having emphasized the importance of graphical tools, the
statement of purpose is not in fact graphical but narrative text!
However, it is very short, normally just a few lines long, and
simply explains the purpose of the system