Posted by cwdjrxyz on 04/23/07 20:57

On Apr 23, 12:20 pm, Andy Dingley <ding...@codesmiths.com> wrote:
> On 23 Apr, 16:03, cwdjrxyz <spamtr...@cwdjr.info> wrote:
>
> > The W3C often uses the word "should" for things that are nice to do,
> > at least in many cases, but they are not absolutely required.
>
> Go read RFC2119

In case anyone is interested in it and does not wish to look at tons
of documents on Google, the following should be enough for most people
who are not on groups writing standards.

_________________________________________________________________________________________________

Network Working Group S.
Bradner
Request for Comments: 2119 Harvard
University
BCP: 14 March
1997
Category: Best Current Practice


Key words for use in RFCs to Indicate Requirement Levels

Status of this Memo

This document specifies an Internet Best Current Practices for the
Internet Community, and requests discussion and suggestions for
improvements. Distribution of this memo is unlimited.

Abstract

In many standards track documents several words are used to signify
the requirements in the specification. These words are often
capitalized. This document defines these words as they should be
interpreted in IETF documents. Authors who follow these guidelines
should incorporate this phrase near the beginning of their
document:

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.

Note that the force of these words is modified by the requirement
level of the document in which they are used.

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.





Bradner Best Current Practice [Page
1]

RFC 2119 RFC Key Words March
1997


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.)

______________________________________________________________________________



> > some old tags are depreciated
>
> deprecated
>
> Different meaning.

Correct. I have an extra "i" in the word.

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