Preface

This book is an introduction to a new class of design pattern, the Elemental Design Patterns, which form a foundation for the study and application of software engineering design patterns. Its foundations are in research into the very fabric of software programming theory, but it is intended to be practical and pragmatic. It is intended for both the beginning programmer and the seasoned developer. It should help students engage with the software industry and give researchers new points to ponder.

In short, this book is meant to be used.

By the end of it, you should have a new set of tools in your toolbelt, a richer understanding of some of the basic concepts of programming that we all use every day, and knowledge of how they relate and interact with one another to do amazing things. The Elemental Design Patterns, or EDPs, are a collection of fundamental programming ideas that we use reflexively and probably don’t think twice about when doing so. This body of work gives them explicit descriptions, regularized names to use in discussions, and a framework for using them in concert and for comparing them on their own merits. If you’re a new student, you’ll learn that instead of facing the ever-growing design patterns literature as a collection of daunting all-or-nothing blocks, you have a chance to take them on piece by piece and gradually understand the literature in a methodical way. If you’re an old hand at software design and patterns, you’ll find new ways to look at old approaches and see new opportunities for our discipline.

This book assumes you have a passing familiarity with design patterns as a field but have not used or studied them in detail. Knowing that they exist and having a brief colloquial knowledge of what they are is enough to start the discussion. The book does not assume you have a background in programming theory, language design, or even a strong one in object-oriented programming, just a desire to learn how to think critically about software design. These subjects will be touched on but only as a starting point for those interested in diving deeper into them through the provided references. The Unified Modeling Language is used to describe small examples, and I suggest either [20] or [33] as references if you do not already know UML. You should have a basic foundation in programming, either procedural or object oriented. The latter will help, but it’s not absolutely required—this text provides much of the necessary information to explain object-oriented programming in easily digestible chunks. Developers experienced with object-oriented systems may still be surprised at finding new perspectives on concepts that they thought they had mastered long ago and a greater appreciation for object-oriented programming as a whole.

Many programmers see the “design patterns community” as an esoteric body of experts and one that they themselves are not a part of. By giving you a new perspective on what can constitute a design pattern, this book should convince you that every programmer is a member of the design patterns community, whether they know it or not. Every single programmer uses design patterns every time they write a line of code, even if don’t think of it that way. Nor are they likely to realize the options they have at their disposal. Design patterns are the shared conceptual space in which we write the electronic dreams that shape our world. It’s time we had a map of the landscape in which we work and play.

Following the example of the seminal Gang of Four text [21], this book is divided into two sections. First is a discussion of why this book was written and who it is written for and an explanation of what EDPs are, where they came from, and why they’re important. This section explains the rationale, the why, behind the EDPs. Next is an introduction to the Pattern Instance Notation, a diagramming system for working with patterns at many levels of granularity and in a multitude of environments. Wrapping up this first section is a discussion of how EDPs can be used to build up to, and in conjunction with, the greater design patterns literature. The second section of the book is a collection of design patterns, starting with the EDPs and working through examples of how they combine to form Intermediate patterns, and finally, a selection of the Gang of Four patterns recast as EDP compositions. The EDPs presented here are only a portion of the EDP Catalog, a collection of the first round of defined and described fundamental patterns. The software engineering community will continue to define and refine additional EDPs as the underlying concepts take root. I hope you decide to help in the endeavor.

Welcome, it’s good to have you join us.