Patterns: what, why, and how

Richard Mitchell and Franco Civello
University of Brighton

A 75-minute tutorial on patterns.

Who's it for?

The tutorial is aimed at people who have heard the noise about object-oriented design patterns (such as those in the book by Gamma et al) but who have not yet looked at individual patterns, or how they might be used in a particular design.

What's the point of patterns?

Here's a picture (followed by the 100 words it's worth).

Software design often involves trade-offs. For example, you could design a piece of software so that it was really easy to build, but quite hard to extend to meet future requirements. Or, you could use more sophisticated techniques that made it harder to build, but easier to extend thereafter.

Sometimes, it is possible to lessen the effect of this kind of trade-off by doing some work at a strategic level. Here are some examples:

build a user interface using a GUI-builder
build a workflow system using a workflow language
build a DP system using SQL
build any program using design patterns.

The diagram illustrates the last example.

How will the tutorial work?

We'll take you through the design of parts of a drawing editor, asking you to think about the design choices along the way, and to make suggestions for improvements.

Then we'll show how using well-understood patterns makes the design quicker and easier to do, and easier to discuss with colleagues.

For the examples, we'll use UML class diagrams and some C++/Java-style code.

Key topics

We'll cover:

The idea of a pattern
Three specific patterns
- Template pattern
- Factory method pattern
- Strategy pattern
How common software mechanisms can be implemented in common code
How algorithms can usefully be turned into objects

What will you go away with?

You'll be given

a small catalogue of patterns
screen shots of the editor at work
outlines of designs that use patterns
a short list of sources of more information.

Less tangibly, we hope you'll go away feeling confident to start exploring the literature of patterns, and to start thinking about where to use them in your own work.

Who are the presenters?

Richard Mitchell and Franco Civello are members of the IT Faculty at the University of Brighton.

They've been teaching and carrying out research into object technology since about 1990. They also have many satisfied commercial clients.