Chapter 1. Pattern Essentials

What's new here is that there's nothing new here. Patterns are about what works. Patterns give us a way to talk about what works.

Brian Foote, pattern writer (1997, ix)

What are patterns? Why are patterns important, and why are they useful? These are the questions answered in this chapter.

Although an explanation of understanding patterns is given, using patterns well requires an understanding of the background to the form itself more so than for any other tool in the software development arsenal.

Patterns hide a lot of cultural and conceptual "baggage," providing a compressed intensity and an economy of expression in return. Patterns users who experience the power of patterns have acquired this baggage, either tacitly (through repeated use) or explicitly, by studying the literature. This is the opposite of models, for which syntax and semantics act as decoder rings for the model message. But it also explains the complementarity of models and patterns as tools for successful and quality-focused software development.

So, this chapter introduces the baggage as part of how to use the book. Later on, there is a more personalized account of a technical subject(see Chapter 9, "Patterns in Context" ). But be warned. This book is conceived as a starting point for a journey, and if you want to make that journey, both chapters are necessary. Fortunately, unlike in real life, the baggage gets lighter along the way.