Re: [ietf-822] Expires header field

[Dave Crocker <[e-mail]>]

On 12/2/2022 12:02 PM, Keith Moore wrote:
> an MUA may present the message in such a way as to reflect the 
> message's decreased relevance.

This is MUA guidance.  Within a specification, it implies guidance to 
show this information and to distinguish it.  This is UI/UX design 
guidance and, again, the IETF generally shouldn't do it, because the 
IETF generally isn't skilled at such issues.

Also, strictly in terms of specification language, it is in the style of 
normative guidance (lack of caps notwithstanding) and implies that the 
MUA's choices about showing increased or decreased relevance otherwise 
has been restricted.


So...

The Expires message header field indicates a date-time after which the 
author of the message believes that the message no longer has primary 
relevance to its intended recipient(s).  This field SHOULD NOT be 
interpreted by intermediate systems (such as relaying MTAs or delivery 
agents) and SHOULD NOT be used to trigger automatic deletion of the message.

This is simpler, cleaner, and better-scoped.

However... on reflection, the SHOULD NOT restriction strikes me as 
excessive.  To the extent there should be language pertaining to 
automated actions, I'd instead suggest adding non-normative language 
about the issues concerning taking automated actions upon expiry.


d/

-- 
Dave Crocker
Brandenburg InternetWorking
bbiw.net
mast:@[e-mail]