Re: [Json] What does "break compatibility" mean?

Paul Hoffman <paul.hoffman@vpnc.org> Thu, 28 February 2013 21:51 UTC

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To: Nico Williams <nico@cryptonector.com>
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Cc: Barry Leiba <barryleiba@computer.org>, json@ietf.org
Subject: Re: [Json] What does "break compatibility" mean?
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On Feb 28, 2013, at 12:46 PM, Nico Williams <nico@cryptonector.com> wrote:

> On Thu, Feb 28, 2013 at 2:06 PM, Tim Bray <tbray@textuality.com> wrote:
>> It’s clear to me that, *for the purposes of the IETF*, someone needs to say
>> “People sending JSON MUST NOT use duplicate keys.”  The fact that certain
>> libraries allow less-clueful developers to do this, and that parsing
>> software is observed to behave unpredictably when they do, should only
>> encourage us.
> 
> The obvious compromise is to say senders MUST NOT send dup object keys
> and receivers MUST take the last key value pair of any dup keys,
> per-ECMAScript.  The latter preserves compatibility.

...but the former ("say senders MUST NOT send dup object keys") breaks it, given that the RFC had a SHOULD not a MUST. Thus the question in this thread.

--Paul Hoffman