Design Patterns Explained

CHAPTER 13
The Principles and
Strategies of Design Patterns
Overview
Previously, I described how design patterns can be used at both the
local and global levels. At local levels, patterns tell us how to solve
particular problems within the context of the patterns. At global
levels, patterns create a map of how the components of the application
interrelate with one another. One way to study design patterns is
to learn how to use them more effectively at both the local and
global levels. They will give you tools to get a better handle on your
problem.
Another way to study design patterns is learn their mechanisms
and the principles and strategies that underlie them. Learning these
will improve your abilities as an analyst and designer. You will
know what to do even in situations when a design pattern has not
yet been developed, because you will already have the building
blocks needed to solve the problem.
In this chapter,
• I describe the open-closed principle, which underlies many
design patterns.
• I discuss the principle of designing from context, which was an
initial objective of Alexander's patterns.
• I discuss the principle of containing variation.
In this chapter
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