Re: [Cbor] πŸ”” WGLC on draft-ietf-cbor-array-tags-03

Jeffrey Yasskin <jyasskin@chromium.org> Fri, 08 March 2019 01:03 UTC

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From: Jeffrey Yasskin <jyasskin@chromium.org>
Date: Thu, 7 Mar 2019 17:03:37 -0800
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To: Francesca Palombini <francesca.palombini@ericsson.com>
Cc: "cbor@ietf.org" <cbor@ietf.org>, "draft-ietf-cbor-array-tags@ietf.org" <draft-ietf-cbor-array-tags@ietf.org>
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Subject: Re: [Cbor] =?utf-8?q?=F0=9F=94=94_WGLC_on_draft-ietf-cbor-array-tags?= =?utf-8?q?-03?=
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This generally looks good to me, with decreasing confidence as the
document gets farther from the simple typed-array use case in its
title. A couple comments below:

1. The document justifies itself with "performance" improvements, but
I believe the tags also save the space overhead of encoding a type for
each element or nested array.

2. It's not clear on the first reading that
https://tools.ietf.org/html/draft-ietf-cbor-array-tags-03#section-3.1
defines two different tags. I'd appreciate either a subsection for tag
1040 or parallel subsections for the two tags.

3. The definition of tag 40 ends with "Data in the Typed Array byte
string …", but the second sub-array doesn't need to be a Typed Array.

4. The definition of tag 1040 starts with "Note" making it look
non-normative. I'd rather have that paragraph define the meaning of
the data item, like "The data item is interpreted the same as in tag
40 except that the second sub-array holds elements with the first
dimension contiguous (column-major order)."

5. The reference to Section 7.1 of [TypedArrayUpdate] is out of date.

6. It's not clear to me that representing the source of the elements
in a uint8 array is worth the confusion of re-using the
is-little-endian bit. What's a use case? It exists in Javascript to
define how assignment works, but one does not assign to CBOR data.

7. What's the use case for the homogenous array tag? Tags, in general,
are mostly useful for generic parsers: do we have an example of one of
those that's going to add a new set of homogenous array types for its
consumers to have to check for?

Jeffrey

On Wed, Mar 6, 2019 at 4:53 AM Francesca Palombini
<francesca.palombini@ericsson.com>; wrote:
>
> CBOR WG,
>
> The chairs believe the array-tags document is ready for WGLC: https://tools.ietf.org/html/draft-ietf-cbor-array-tags-03
>
> The WGLC will end by *20th of March*, please make sure to send your comments to the list before then.
>
> Best regards,
> Francesca & Barry
>
> ο»ΏOn 05/03/2019, 23:58, "CBOR on behalf of Carsten Bormann" <cbor-bounces@ietf.org on behalf of cabo@tzi.org>; wrote:
>
>     -03 reflects the fact that IANA has made the allocations.
>
>     From this author’s point of view, we are ready for WGLC.
>
>     Grüße, Carsten
>
>
>     > On Mar 5, 2019, at 23:55, internet-drafts@ietf.org wrote:
>     >
>     >
>     > A New Internet-Draft is available from the on-line Internet-Drafts directories.
>     > This draft is a work item of the Concise Binary Object Representation Maintenance and Extensions WG of the IETF.
>     >
>     >        Title           : Concise Binary Object Representation (CBOR) Tags for Typed Arrays
>     >        Authors         : Johnathan Roatch
>     >                          Carsten Bormann
>     >   Filename        : draft-ietf-cbor-array-tags-03.txt
>     >   Pages           : 14
>     >   Date            : 2019-03-05
>     >
>     > Abstract:
>     >   The Concise Binary Object Representation (CBOR, RFC 7049) is a data
>     >   format whose design goals include the possibility of extremely small
>     >   code size, fairly small message size, and extensibility without the
>     >   need for version negotiation.
>     >
>     >   The present document makes use of this extensibility to define a
>     >   number of CBOR tags for typed arrays of numeric data, as well as two
>     >   additional tags for multi-dimensional and homogeneous arrays.  It is
>     >   intended as the reference document for the IANA registration of the
>     >   CBOR tags defined.
>     >
>     >
>     > The IETF datatracker status page for this draft is:
>     > https://datatracker.ietf.org/doc/draft-ietf-cbor-array-tags/
>     >
>     > There are also htmlized versions available at:
>     > https://tools.ietf.org/html/draft-ietf-cbor-array-tags-03
>     > https://datatracker.ietf.org/doc/html/draft-ietf-cbor-array-tags-03
>     >
>     > A diff from the previous version is available at:
>     > https://www.ietf.org/rfcdiff?url2=draft-ietf-cbor-array-tags-03
>     >
>     >
>     > Please note that it may take a couple of minutes from the time of submission
>     > until the htmlized version and diff are available at tools.ietf.org.
>     >
>     > Internet-Drafts are also available by anonymous FTP at:
>     > ftp://ftp.ietf.org/internet-drafts/
>     >
>     > _______________________________________________
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>     > https://www.ietf.org/mailman/listinfo/i-d-announce
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>     > or ftp://ftp.ietf.org/ietf/1shadow-sites.txt
>     >
>
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