A Note About Conventions Used in This Book

In the writing of this book, we had to make several choices about style and convention. Some of our choices have surprised our readers. So, it is worth a few comments about why we have chosen to do what we have done.

Approach Rationale
First person voice This book is a collaborative effort between two authors. We debated and refined our ideas to find the best ways to explain these concepts. Alan tried them out in his courses and we refined some more. We chose to use the first person singular in the body of this book because it allows us to tell the story in what we hope is a more engaging and natural style.
Scanning text We have tried to make this book easy to scan so that you can get the main points even if you do not read the body, or so that you can quickly find the information you need. We make significant use of tables and bulleted lists. We provide text in the outside margin that summarizes paragraphs. With the discussion of each pattern, we provide a summary table of the key features of the pattern. Our hope is that these will make the book that much more accessible.
Code fragments This book is about analysis and design more than implementation. Our intent is to help you think about crafting good designs based on the insights and best practices of the object-oriented community, as expressed in design patterns. One of the challenges for all of us programmers is to avoid going to the implementation too early, doing before thinking. Knowing this, we have purposefully tried to stay away from too much discussion on implementation. Our code examples may seem a bit lightweight and fragmentary. Specifically, we never provide error checking in the code. This is because we are trying to use the code to illustrate concepts.
Strategies and principles Ours is an introductory book. It will help you be able to get up to speed quickly with design patterns. You will understand the principles and strategies that motivate design patterns. After reading this book, you can go on to a more scholarly or reference book. The last chapter will point you to many of the references that we have found useful.
Show breadth and give a taste We are trying give you a taste for design patterns, to expose you to the breadth of the pattern world but not go into depth in any of them (see the previous point). Our thought was this: If you brought someone to the USA for a two week visit, what would you show them? Maybe a few sites to help them get familiar with architectures, communities, the feel of cities and the vast spaces that separate them, freeways, and coffee shops. But you would not be able to show them everything. To fill in their knowledge, you might choose to show them slide shows of many other sites and cities to give them a taste of the country. Then, they could make plans for future visits. We are showing you the major sites in design patterns and then giving you tastes of other areas so that you can plan your own journey into patterns.

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