Allen Wirfs-Brock wrote:
The ES5 spec. for JSON.parse requires (ie MUST accept) that duplicate
keys are accepted and that the value associated with the last
duplicated key wins. A valid implementation of JSON.parse MUST not
reject such JSON strings.
IETF has SHOULD as well as MUST, though. Normative specs can say what
must happen, but also what should happen in a clean-slate or ideal-world
setting. The Internet evolved with Postel's Law falling out of the process.
Previously you wrote:
> I would be willing to [lose] the first sentence (containing the
SHOULD) entirely as it doesn't add any real normative value.
But normative RFCs/internet-drafts that use SHOULD not MUST still have
value.
From http://tools.ietf.org/html/rfc2119
1 <http://tools.ietf.org/html/rfc2119#section-1>. MUST
This word, or the terms "REQUIRED" or "SHALL", mean that the
definition is an absolute requirement of the specification.
2 <http://tools.ietf.org/html/rfc2119#section-2>. MUST NOT
This phrase, or the phrase "SHALL NOT", mean that the
definition is an absolute prohibition of the specification.
3 <http://tools.ietf.org/html/rfc2119#section-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 <http://tools.ietf.org/html/rfc2119#section-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 <http://tools.ietf.org/html/rfc2119#section-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.)
6 <http://tools.ietf.org/html/rfc2119#section-6>. Guidance in the
use of these Imperatives
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 retransmissions) For
example, they must not be used to try to impose a particular method
on implementors where the method is not required for
interoperability.
/be
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