[core] Artart last call review of draft-ietf-core-senml-data-ct-04

Bron Gondwana via Datatracker <noreply@ietf.org> Wed, 25 August 2021 13:30 UTC

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Subject: [core] Artart last call review of draft-ietf-core-senml-data-ct-04
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Reviewer: Bron Gondwana
Review result: Ready with Nits

This is a last-call review as part of the ARTART review team, of the document

This document describes an extension to RFC 8428 (SenML) to indicate the media
type and content-coding.

It is mostly easy to understand, however there is a missing reference to one
registry, and some phrases that may be confusing.

The missing registry is here:
(I found it by following normative references, however other similarly
registered data fields in this document link to their registries, and could
likewise be found by following references)

The document specifies `Content-Coding` as:

   Content-Coding:  a registered name for an encoding transformation
      that has been or can be applied to a representation.  Confusingly,
      in HTTP the Content-Coding is then given in a header field called
      "Content-Encoding"; we *never* use this term (except when we are
      in error).

I found this quite confusing, and it also comes across as very snarky and
suggesting infighting.  I suggest removing the "except when we are in error"

I also found "has been or can be" is also confusing.  In the context of this
document, I understood Content-Coding in a `ct` field to mean that said coding
HAS BEEN applied to the value in `vd`, however this wording makes me question
that assumption.

Maybe something like this is sufficient?

Content-Coding: a name registered in [IANA.content-coding] as specified by
[RFC7230].  Confusingly, in HTTP the Content-Coding is found in a field called
"Content-Encoding", however "Content-Coding" is the correct term.

The other confusing section was this in section 3:

  If no "@" sign is present outside the media type parameters, the
  Content-Coding is not specified and the "identity" Content-Coding is used -- 
  no encoding transformation is employed.

"If no @ sign is present outside" is a really clunky turn of phrase that left
me more confused than the examples!  I assume this construction was used
because theoretically an '@' sign could be present inside the media-type, or
inside a parameter, if correctly quoted.  I would suggest at least changing
"present outside" to after, or trailing, or something.

Maybe this?

If no "@" sign is present after the media-type parameters, then no
Content-Coding has been specified, and the "identity" Content-Coding is used --
no encoding transformation is employed.

Other than those two slightly confusing bits, great document - I enjoyed
reading it and the intentions, purpose and use of this document are clear.