Nesdev wiki:Manual of Style/RFC 2119

MUST SHOULD MAY

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119. (what's this?)

"RFC 2119: Key words for use in RFCs to Indicate Requirement Levels" is a RFC memorandum published by the Internet Engineering Task Force that describes the standard meanings of modal verbs and some other words used in Internet standards documents. Documents that use RFC 2119 indicate that RFC 2119 applies to a given word by writing the word with all capital letters.

The most common key words are

MUST or MUST NOT

Something is absolutely required.

SHOULD or SHOULD NOT

Something is strongly recommended.

MAY

Something is allowable either way.

Not all pages on this wiki need to indicate requirement levels. Pages that are descriptive rather than prescriptive, that is, those that describe what is rather than what ought to be, need not use this convention. But pages that do indicate requirement levels SHOULD use this convention and SHOULD use the template {{RFC 2119}}, which produces a notice that floats to the right, lest readers confuse these all-capital words with shouting.