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Re: [Cbor] A CBOR tag for alternatives/unions, request for comments

chrysn <chrysn@fsfe.org> Wed, 23 February 2022 16:10 UTC

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Date: Wed, 23 Feb 2022 17:09:49 +0100
From: chrysn <chrysn@fsfe.org>
To: Carsten Bormann <cabo@tzi.org>
Cc: Michael Peyton Jones <michael.peyton-jones@iohk.io>, Duncan Coutts <duncan@well-typed.com>, cbor@ietf.org, Jared Corduan <jared.corduan@iohk.io>, Alexander Byaly <alexander.byaly@iohk.io>
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Subject: Re: [Cbor] A CBOR tag for alternatives/unions, request for comments
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Hello Carsten,

On Wed, Feb 23, 2022 at 02:16:14PM +0100, Carsten Bormann wrote:
> If we have time in the CBOR meeting today (very likely) and you have
> time and comments, we could complete the discussion and ask IANA to
> register.

I think the text should caution the user to say something about the
alternative number stability, maybe extending the Semantics section like
this:

| Protocols that use these tags should consider and document two factors
| that influence an alternative's interpretation:
| 
| * Postion. In some protocols, the meaning of an enumerated alternative
|   will depend on the location in the data item surrounding it. This is
|   especially true of protocols that incorporate other protocols.
| 
| * Stability. Whereas interchange protocols are expected to specify
|   semantics for alternatives in a future-proof way, other use cases
|   (such as debug information or crash recovery) may use alternatives
|   whose meaning is only stable within a software release, or even only
|   for a single build.

BR
Christian

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