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Re: RFC 2119 terms, ALL CAPS vs lower case

2012-05-20 02:40:29

On Sat, 2012-05-19, Brian E Carpenter wrote:
On 2012-05-19 20:39, Ofer Inbar wrote:
...

 But don't change the rules.  2119 works well as is IMO.

Just to be clear about the current rules, 2119 makes it clear that
upper case keywords are optional ("These words are often capitalized").
Indeed, numerous standards track documents don't use them.

I do not agree that 2119 is "clear" on this topic. I read the
beginning of the first paragraph of the Abstract as:

Some background motivation:

  In many standards track documents several words are used to
  signify the requirements in the specification. These words are
  often capitalized.

A new proposal:

  This document defines these words as they should be interpreted
  in IETF documents.

Thus, it is defining a new, unified convention for documenting 
requirements language.

And then the boilerplate shows all of the requirement words in 
uppercase, obviously convincing a lot of people that the new 
standard is to use them in uppercase when their meaning is 
normative.

As one example, in section 6 the text reads:

   Imperatives of the type defined in this memo must be used with care
   and sparingly.  In particular, they MUST only be used where it is
   actually required for interoperation or to limit behavior which has
   potential for causing harm (e.g., limiting retransmisssions)  For
   example, they must not be used to try to impose a particular method
   on implementors where the method is not required for
   interoperability.

There is one instance of "MUST" and two of "must" in this 
paragraph. I would observe that the "MUST" is used to define a 
requirement upon RFC texts, but the two "must"s are used to 
try to affect the motivation of the humans writing the RFC texts.

There are examples elsewhere in 2119 of the use of these words in
lowercase that seem NOT be used in a normative way.

If anything I would evaluate the evidence to indicate that the 
distinction of case *was intended* to be meaningful.

-- 
Bill McQuillan <McQuilWP(_at_)pobox(_dot_)com>