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Re: [Sedate] Distinguishing "optional extra" vs "you need to understand this to process the date accurately" extensions

Carsten Bormann <cabo@tzi.org> Thu, 09 December 2021 14:59 UTC

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From: Carsten Bormann <cabo@tzi.org>
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Date: Thu, 09 Dec 2021 15:59:46 +0100
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To: Bron Gondwana <brong@fastmailteam.com>
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Subject: Re: [Sedate] Distinguishing "optional extra" vs "you need to understand this to process the date accurately" extensions
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On 2021-12-09, at 14:04, Bron Gondwana <brong@fastmailteam.com> wrote:
> 
> So I wonder if we need a syntax to say "if this extension is not recognized by the receiving system, it SHOULD throw an error and MUST NOT expect the date to be exact" - either a reserved namespace for such extensions, or some other syntactical sugar.

Protocols typically have a way to distinguish “critical” (or “must-understand”) options from “elective” options.  Sometimes, the distinction is baked into the option code, sometimes there is separate place (which also allows the same option to be used in both ways).  Our syntax should provide an easy way to do the latter, as in:

   1996-12-19T16:39:57-08:00[America/Los_Angeles][u-ca=hebrew]
(Elective, ignore option if not understood)

   1996-12-19T16:39:57-08:00[America/Los_Angeles][u-ca!hebrew]
(Critical, must understand/must reject date if not understood)

Well, we need better examples...

Grüße, Carsten

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