Guidelines with the following characteristics are easier to understand and use. At a minimum, when writing a new guideline, it should be
|Understandable and unambiguous|
A guideline's description should be precise, clearly worded, concise, and should define a characteristic of a model (or part of a model) that a checking tool can evaluate. Use the words "must," "shall," "should," and "may" carefully; they have distinct meanings that are important for model developers and model checkers (human and automated). It is helpful to the reader if the guideline author describes how the conforming state can be reached (for example, by selecting particular options or clicking a certain button). Examples, counterexamples, pictures, diagrams, and screen shots are also helpful and are encouraged.
Minimize the allowable exceptions to a guideline; exceptions blur a guideline and make it harder to apply. If a guideline has many allowable exceptions, you may be trying to cover too many characteristics with one guideline. (See Minimal, following, for some solutions.)
|Easy to find|
A guideline should address only one model characteristic at a time. Guidelines should be atomic. For example, instead of writing a big guideline that addresses error prevention and readability at the same time, make two guidelines, one that addresses error prevention and one that addresses readability. If appropriate, make one guideline a prerequisite of the other. Also, big guidelines are more likely than small guidelines to require compromises for wide acceptance. Big guidelines may end up being weaker, less specific, and less beneficial. Small, focused guidelines are less likely to change due to compromise and easier adoption.