This guide is divided into several sections such as each one tries to group related conventions. For example, all database-related convention is grouped in the same section. Each of the convention have the following keywords, which indicates how important it is to comply with such convention:
MUST This word, or the terms “REQUIRED” or “SHALL”, mean that the definition is an absolute requirement of the specification.
MUST NOT This phrase, or the phrase “SHALL NOT”, mean that the definition is an absolute prohibition of the specification.
SHOULD This word, or the adjective “RECOMMENDED”, mean that there may exist valid reasons in particular circumstances to ignore a particular item, but the full implications must be understood and carefully weighed before choosing a different course.
SHOULD NOT This phrase, or the phrase “NOT RECOMMENDED” mean that there may exist valid reasons in particular circumstances when the particular behavior is acceptable or even useful, but the full implications should be understood and the case carefully weighed before implementing any behavior described with this label.
MAY This word, or the adjective “OPTIONAL”, mean that an item is truly optional.
the above specifications is derived from RFC 2119