rfc-2119

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RFC 2119

Microformat specifications (and their drafts) use the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL". These are to be interpreted as described in RFC2119 and MAY include a link to this page, or directly to http://www.ietf.org/rfc/rfc2119.txt.

Definitions

RFC 2119 gives the following definitions:

  1. MUST This word, or the terms "REQUIRED" or "SHALL", mean that the definition is an absolute requirement of the specification.
  2. MUST NOT This phrase, or the phrase "SHALL NOT", mean that the definition is an absolute prohibition of the specification.
  3. 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.
  4. 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.
  5. MAY This word, or the adjective "OPTIONAL", mean that an item is truly optional. One vendor may choose to include the item because a particular marketplace requires it or because the vendor feels that it enhances the product while another vendor may omit the same item. An implementation which does not include a particular option MUST be prepared to interoperate with another implementation which does include the option, though perhaps with reduced functionality. In the same vein an implementation which does include a particular option MUST be prepared to interoperate with another implementation which does not include the option (except, of course, for the feature the option provides.)

Templates

The following templates are available for use on this wiki:

These adhere to the W3C Manual of Style guidelines for RFC 2119.

Markup suggestions

When using RFC 2119 terms on web pages, consider re-using the mark-up pattern from the W3C Manual of Style (in particular class="RFC2119" - note capitalization), and perhaps their suggested style rule as well.

On this wiki, the above templates help facilitate the use of the markup pattern from the W3C Manual of Style.

In addition, for marking up the commonly used initial paragraph declaring RFC 2119 terms in documents, consider using the following markup, proposed by Edward O'Connor:

   <p>
     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 <a
     href="http://www.ietf.org/rfc/rfc2119.txt"
     rel="help glossary">RFC 2119</a>.
   </p>

microformat thoughts

Some have suggested considering a new microformat for marking up use of RFC 2119 terms.

It appears there is no need for such a new microformat however. Following W3C's established practice, and Edward O'Connor's POSH suggestion for the initial paragraph, appears to be sufficient.

rfc-2119 was last modified: Monday, January 7th, 2008

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