[Cbor] "Ignore unknown" -- Re: [core] WG Last Call on draft-ietf-core-problem-details

[Carsten Bormann <[e-mail]>]

> * "MUST ignore": From recent chats I understand that it does not only
>  refers to keys (standard, outer and inner custom) the receiver does
>  not recognize, but also to values outside the expected set.
> 
>  If that is the case, it would be good to have a few words of rationale
>  and guidance, as "on error goto next" patterns are often discouraged
>  -- I think they're good here, but other readers might need convincing.

This is much more widely open (and, thus, subject to interpretation) than simply ignoring unknown map keys.
How strict does the implementation need about checking the values so it can ignore an unexpected value?  Can the originator rely on this check having been properly made?
Big can of worms.
Not sure this spec is the place to develop the general solution.
(In practice, ignore unknown works reasonably well, so I don’t see the pain that would justify such a fundamental effort.)

Grüße, Carsten