To raise a “rule of thumb” to the status of design pattern, it must be formalized. Christopher Alexander stated that a design pattern must contain at least the following four aspects: a name, a problem statement, a proposed solution, and the consequences of using the pattern. The “Gang of Four” patterns have even more aspects, which are meant to further clarify the problem domain and proposed solution. The design pattern template used in this text mimics the Gang of Four format, with slight modifications appropriate for role-playing game design.
If the pattern has a succinct and commonly known name, use it. Otherwise, make the name short and descriptive. A good name is crucial, because it becomes the definitive term used to reference the pattern in future discussions. Because design patterns are neither “appropriate” or “inappropriate” for a game without first knowing the designer’s goals, their names should be neutral rather than connote a value judgment.
Provide a short statement (one or two sentences at most) describing the rationale for the pattern’s existence. What does it accomplish? What problem does it solve?
Give any other common names used for referencing the pattern.
Provide references to any similar patterns that should be considered as alternatives when this pattern is considered.
Provide a detailed description of the problem being addressed by the pattern and its solution. This description may be as lengthy as necessary to describe the problem being addressed.
Provide a diagram of the participants in the pattern. Most of the diagrams in this book are gauge diagrams. The diagrams abstract away details to expose the underlying structure.
Provide a list of criteria of when to use the pattern. When can it be applied? What kinds of poor designs does the pattern address? What are the alternatives?
Provide descriptions of the consequences of using the pattern, both good and bad.
Provide descriptions of what practical design issues should be considered when applying the pattern.
Provide examples of using the pattern. Keep the examples as simple as possible to illustrate only the key points.
Reference games using the pattern and explain how they use it. This need not be an exhaustive list of all known instances of use, but rather a sampling of uses that covers the broadest possible spectrum of current application. There should be at least 2 examples in this section to ensure that the pattern is, in fact, a pattern and not just a single-use idea (however brilliant).