From: Steve Lhomme <slhomme@matroska.org>
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Date: Sun, 11 Jan 2026 11:44:38 +0100
In-Reply-To: 
 <176760281350.3304339.9509637392974117767@dt-datatracker-5656579b89-p6k4r>
To: =?utf-8?Q?=C3=89ric_Vyncke?= <evyncke@cisco.com>
References: 
 <176760281350.3304339.9509637392974117767@dt-datatracker-5656579b89-p6k4r>
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CC: The IESG <iesg@ietf.org>, cellar-chairs@ietf.org, cellar@ietf.org,
 draft-ietf-cellar-tags@ietf.org, spencerdawkins.ietf@gmail.com
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Subject: =?utf-8?q?=5BCellar=5D_Re=3A_=C3=89ric_Vyncke=27s_Discuss_on_draft-ietf-cell?=
	=?utf-8?q?ar-tags-20=3A_=28with_DISCUSS_and_COMMENT=29?=
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 <https://mailarchive.ietf.org/arch/msg/cellar/6la3CAjSVA1w-P0HA8yJx2YPb6Y>


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Hi Eric and thanks for your review,

My comments are inline below.

> On 5 Jan 2026, at 09:46, =C3=89ric Vyncke via Datatracker =
<noreply@ietf.org> wrote:
>=20
> =C3=89ric Vyncke has entered the following ballot position for
> draft-ietf-cellar-tags-20: Discuss
>=20
> When responding, please keep the subject line intact and reply to all
> email addresses included in the To and CC lines. (Feel free to cut =
this
> introductory paragraph, however.)
>=20
>=20
> Please refer to =
https://www.ietf.org/about/groups/iesg/statements/handling-ballot-position=
s/=20
> for more information about how to handle DISCUSS and COMMENT =
positions.
>=20
>=20
> The document, along with other ballot positions, can be found here:
> https://datatracker.ietf.org/doc/draft-ietf-cellar-tags/
>=20
>=20
>=20
> ----------------------------------------------------------------------
> DISCUSS:
> ----------------------------------------------------------------------
>=20
>=20
> # =C3=89ric Vyncke INT AD comments for draft-ietf-cellar-tags-20
> CC @evyncke
>=20
> Thank you for the work put into this document even if I find a little =
weird to
> have tag definitions of a container done in a codec WG, but it fits =
the CELLAR
> WG charter, so all is good.

What is now RFC9559 originally had the tags and codec definition into a =
single document (and even some other things). We split in the document =
so we can work on the main one faster.

> Please find below some blocking DISCUSS points (easy to address), some
> non-blocking COMMENT points/nits (replies would be appreciated even if =
only for
> my own education).
>=20
> Special thanks to Spencer Dawkins for the shepherd's detailed write-up
> including the WG consensus (albeit a small WG it seems) and the =
justification
> of the intended status.
>=20
> I hope that this review helps to improve the document,
>=20
> Regards,
>=20
> -=C3=A9ric
>=20
> Note: this ballot comments follow the Markdown syntax of
> https://github.com/mnot/ietf-comments/tree/main, i.e., they can be =
processed by
> a tool to create github issues.
>=20
> ## DISCUSS (blocking)
>=20
> As noted in
> =
https://datatracker.ietf.org/doc/statement-iesg-handling-ballot-positions-=
20220121/,
> a DISCUSS ballot is a request to have a discussion on the points =
below; I
> really think that the document would be improved with a change here, =
but can be
> convinced otherwise.
>=20
> ### Missing version
>=20
> The CELLAR charter includes `Standards Track specification for =
Matroska
> container format version 4` but this I-D, while proposed standard, =
does not
> mention at all the version 4. So, it is really unclear.
>=20
> Note: RFC 9559 section 7 is about versioning, but this I-D should =
really
> mention version 4.

The tags document define the values set in Matroska elements =
\Segment\Tags\Tag\+SimpleTag\TagName, =
\Segment\Tags\Tag\+SimpleTag\TagString and =
\Segment\Tags\Tag\+SimpleTag\TagBinary.
The elements don=E2=80=99t have a =E2=80=9Cminver=E2=80=9D attribute, =
which means they are usable since Matroska v1. That=E2=80=99s why there =
is no versioning mentioned.=20
All the tags, even the ones that don=E2=80=99t exist yet and even =
=E2=80=9Cunofficial=E2=80=9D ones, can be used in files compatible with =
Matroska v1. For apps that interpret tags, they only need to handle the =
names they care about and ignore the (infinite) rest.

> ### Section 3.2.1
>=20
> Happy to be corrected as I am not a UTF-8 expert, but what is the =
exact
> definition of `any space`? again thinking about UTF-8 and
> https://en.wikipedia.org/wiki/Whitespace_character

A similar question was raised about capital letters as there=E2=80=99s =
no proper rule to define what is UTF-8/Unicode capital letter (I can =
find the post anymore).
I can add a link to the wikipedia page if that helps. Now that these =
recommendations are a MUST we could also remove this line altogether, =
since it=E2=80=99s not part of the allowed characters that MUST be used.

> ### Section 4.11
>=20
> `Library of Congress Control Number` but from which country? This =
definition is
> ambiguous.

Addressed here =
https://github.com/ietf-wg-cellar/matroska-specification/pull/1051=20

> ----------------------------------------------------------------------
> COMMENT:
> ----------------------------------------------------------------------
>=20
>=20
> ## COMMENTS (non-blocking)
>=20
> ### Support for others DISCUSS points
>=20
> I second (hence won't repeat) the following DISCUSS points by Med:
> - use of BCP14 in IANA considerations
> - other issues mentioned in the IANA considerations
>=20
> I note though that IANA tagged (punt intended) this I-D as "IANA OK"
>=20
> ### Abstract
>=20
> Abstracts need to be concise but also useful and descriptive. I.e., at =
least
> mention the version (per my DISCUSS point) and be more descriptive.
>=20
> The title should also include "version 4".

No, these tags are usable in all Matroska versions. There is no =
versioning of tag names and values.

> ### Section 1
>=20
> Please expand `EBML` at first use.

What do you mean by =E2=80=9Cexpand=E2=80=9D ? There is a link to the =
"Section 7.7 of [RFC8794]=E2=80=9D in the first sentence where it=E2=80=99=
s used.

> ### Use of personal pronouns
>=20
> Let's avoid the use of personal pronouns such as `if you wanted to =
store`
> (section 3) or `We also need an official list` (section 3.1) or even =
`Our
> recommendations are in between` and `put any tag in your file` =
(section 3.1
> albeit not pronouns ;-) ). I.e., who is the "we" ? The authors ? The =
WG ? The
> IETF ?

Addressed by =
https://github.com/ietf-wg-cellar/matroska-specification/pull/1052=20

> ### Use of 'official'
>=20
> As noted in other ballots, please refrain using `official`, the IETF =
issues
> standards and not laws; so, s/official/standard/ would be much better.

Addressed by =
https://github.com/ietf-wg-cellar/matroska-specification/pull/1048=20

> ### Section 3.2.1
>=20
> `UTF-8 capital letters`, I am not a UTF-8 or internationalisation =
expert, but
> do all alphabets have "capital letters" (and should it be "character" =
rather
> than `letter`)

There is no clear definition of UTF-8 capital letters nor a nice rule to =
apply.

That could be problem if someone proposes tag names in some language =
that don=E2=80=99t have capital letters (chinese ? japanese ?). No sure =
what to do here. We cannot change the =E2=80=9CTagName" type from UTF-8 =
to ASCII anymore. Maybe we could say only latin capital letters ? A lot =
of languages have a latinized version.

> ### Section 3.2.2
>=20
> Why not a MUST in `Multiple items SHOULD NOT`? See also
> =
https://datatracker.ietf.org/doc/statement-iesg-statement-on-clarifying-th=
e-use-of-bcp-14-key-words/

This used to be that way but turned back in =
https://github.com/ietf-wg-cellar/matroska-specification/pull/1030
After the AD review from Orie =
https://mailarchive.ietf.org/arch/msg/cellar/4ebLFttRb_I8SFu5yMQSIDPuk2E/=20=


> ### Section 3.2.2.2
>=20
> A long discussion about the decimal '.' vs. ',', but nothing is =
written in
> which base the "UTF-8 number" is represented. I guess base 10, but =
let's be
> specific. I also wonder why not using a IEEE binary format was not =
used
> (possibly for backward compatibility).

These tag values often correspond to tags found in other systems like =
ID3 where they are stored as strings. So for compatibility with other =
systems we use strings as well. Newer binary formats like the EBU R128 =
are stored as binary.

I added some text to mention it=E2=80=99s in base 10 in =
https://github.com/ietf-wg-cellar/matroska-specification/pull/1053=20

> ### Section 3.3.1
>=20
> Should there be a definition or reference for `TagChapterUID`? (also =
for other
> *UID terms).

I added some text mentioning the ChapterUID which value is used in =
https://github.com/ietf-wg-cellar/matroska-specification/pull/1054=20

Thanks again for your review.
Steve=

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	charset=utf-8

<html><head><meta http-equiv=3D"content-type" content=3D"text/html; =
charset=3Dutf-8"></head><body style=3D"overflow-wrap: break-word; =
-webkit-nbsp-mode: space; line-break: after-white-space;">Hi Eric and =
thanks for your review,<div><br></div><div>My comments are inline =
below.<br id=3D"lineBreakAtBeginningOfMessage"><div><br><blockquote =
type=3D"cite"><div>On 5 Jan 2026, at 09:46, =C3=89ric Vyncke via =
Datatracker &lt;noreply@ietf.org&gt; wrote:</div><br =
class=3D"Apple-interchange-newline"><div><div>=C3=89ric Vyncke has =
entered the following ballot position for<br>draft-ietf-cellar-tags-20: =
Discuss<br><br>When responding, please keep the subject line intact and =
reply to all<br>email addresses included in the To and CC lines. (Feel =
free to cut this<br>introductory paragraph, however.)<br><br><br>Please =
refer to =
https://www.ietf.org/about/groups/iesg/statements/handling-ballot-position=
s/ <br>for more information about how to handle DISCUSS and COMMENT =
positions.<br><br><br>The document, along with other ballot positions, =
can be found =
here:<br>https://datatracker.ietf.org/doc/draft-ietf-cellar-tags/<br><br><=
br><br>-------------------------------------------------------------------=
---<br>DISCUSS:<br>-------------------------------------------------------=
---------------<br><br><br># =C3=89ric Vyncke INT AD comments for =
draft-ietf-cellar-tags-20<br>CC @evyncke<br><br>Thank you for the work =
put into this document even if I find a little weird to<br>have tag =
definitions of a container done in a codec WG, but it fits the =
CELLAR<br>WG charter, so all is =
good.<br></div></div></blockquote><div><br></div><div>What is now =
RFC9559 originally had the tags and codec definition into a single =
document (and even some other things). We split in the document so we =
can work on the main one faster.</div><br><blockquote =
type=3D"cite"><div><div>Please find below some blocking DISCUSS points =
(easy to address), some<br>non-blocking COMMENT points/nits (replies =
would be appreciated even if only for<br>my own =
education).<br><br>Special thanks to Spencer Dawkins for the shepherd's =
detailed write-up<br>including the WG consensus (albeit a small WG it =
seems) and the justification<br>of the intended status.<br><br>I hope =
that this review helps to improve the =
document,<br><br>Regards,<br><br>-=C3=A9ric<br><br>Note: this ballot =
comments follow the Markdown syntax =
of<br>https://github.com/mnot/ietf-comments/tree/main, i.e., they can be =
processed by<br>a tool to create github issues.<br><br>## DISCUSS =
(blocking)<br><br>As noted =
in<br>https://datatracker.ietf.org/doc/statement-iesg-handling-ballot-posi=
tions-20220121/,<br>a DISCUSS ballot is a request to have a discussion =
on the points below; I<br>really think that the document would be =
improved with a change here, but can be<br>convinced =
otherwise.<br><br>### Missing version<br><br>The CELLAR charter includes =
`Standards Track specification for Matroska<br>container format version =
4` but this I-D, while proposed standard, does not<br>mention at all the =
version 4. So, it is really unclear.<br><br>Note: RFC 9559 section 7 is =
about versioning, but this I-D should really<br>mention version =
4.<br></div></div></blockquote><div><br></div><div>The tags document =
define the values set in Matroska =
elements&nbsp;\Segment\Tags\Tag\+SimpleTag\TagName,&nbsp;\Segment\Tags\Tag=
\+SimpleTag\TagString =
and&nbsp;\Segment\Tags\Tag\+SimpleTag\TagBinary.</div><div>The elements =
don=E2=80=99t have a =E2=80=9Cminver=E2=80=9D attribute, which means =
they are usable since Matroska v1. That=E2=80=99s why there is no =
versioning mentioned.&nbsp;</div><div>All the tags, even the ones that =
don=E2=80=99t exist yet and even =E2=80=9Cunofficial=E2=80=9D ones, can =
be used in files compatible with Matroska v1. For apps that interpret =
tags, they only need to handle the names they care about and ignore the =
(infinite) rest.</div><br><blockquote type=3D"cite"><div><div>### =
Section 3.2.1<br><br>Happy to be corrected as I am not a UTF-8 expert, =
but what is the exact<br>definition of `any space`? again thinking about =
UTF-8 =
and<br>https://en.wikipedia.org/wiki/Whitespace_character<br></div></div><=
/blockquote><div><br></div><div>A similar question was raised about =
capital letters as there=E2=80=99s no proper rule to define what is =
UTF-8/Unicode capital letter (I can find the post anymore).</div><div>I =
can add a link to the wikipedia page if that helps. Now that these =
recommendations are a MUST we could also remove this line altogether, =
since it=E2=80=99s not part of the allowed characters that MUST be =
used.</div><br><blockquote type=3D"cite"><div><div>### Section =
4.11<br><br>`Library of Congress Control Number` but from which country? =
This definition =
is<br>ambiguous.<br></div></div></blockquote><div><br></div><div>Addressed=
 here&nbsp;<a =
href=3D"https://github.com/ietf-wg-cellar/matroska-specification/pull/1051=
">https://github.com/ietf-wg-cellar/matroska-specification/pull/1051</a>&n=
bsp;</div><br><blockquote =
type=3D"cite"><div><div>--------------------------------------------------=
--------------------<br>COMMENT:<br>--------------------------------------=
--------------------------------<br><br><br>## COMMENTS =
(non-blocking)<br><br>### Support for others DISCUSS points<br><br>I =
second (hence won't repeat) the following DISCUSS points by Med:<br>- =
use of BCP14 in IANA considerations<br>- other issues mentioned in the =
IANA considerations<br><br>I note though that IANA tagged (punt =
intended) this I-D as "IANA OK"<br><br>### Abstract<br><br>Abstracts =
need to be concise but also useful and descriptive. I.e., at =
least<br>mention the version (per my DISCUSS point) and be more =
descriptive.<br><br>The title should also include "version =
4".<br></div></div></blockquote><div><br></div><div>No, these tags are =
usable in all Matroska versions. There is no versioning of tag names and =
values.</div><br><blockquote type=3D"cite"><div><div>### Section =
1<br><br>Please expand `EBML` at first =
use.<br></div></div></blockquote><div><br></div><div>What do you mean by =
=E2=80=9Cexpand=E2=80=9D ? There is a link to the "Section 7.7 of =
[RFC8794]=E2=80=9D in the first sentence where it=E2=80=99s =
used.</div><br><blockquote type=3D"cite"><div><div>### Use of personal =
pronouns<br><br>Let's avoid the use of personal pronouns such as `if you =
wanted to store`<br>(section 3) or `We also need an official list` =
(section 3.1) or even `Our<br>recommendations are in between` and `put =
any tag in your file` (section 3.1<br>albeit not pronouns ;-) ). I.e., =
who is the "we" ? The authors ? The WG ? The<br>IETF =
?<br></div></div></blockquote><div><br></div><div>Addressed by&nbsp;<a =
href=3D"https://github.com/ietf-wg-cellar/matroska-specification/pull/1052=
">https://github.com/ietf-wg-cellar/matroska-specification/pull/1052</a>&n=
bsp;</div><br><blockquote type=3D"cite"><div><div>### Use of =
'official'<br><br>As noted in other ballots, please refrain using =
`official`, the IETF issues<br>standards and not laws; so, =
s/official/standard/ would be much =
better.<br></div></div></blockquote><div><br></div><div>Addressed =
by&nbsp;<a =
href=3D"https://github.com/ietf-wg-cellar/matroska-specification/pull/1048=
">https://github.com/ietf-wg-cellar/matroska-specification/pull/1048</a>&n=
bsp;</div><br><blockquote type=3D"cite"><div><div>### Section =
3.2.1<br><br>`UTF-8 capital letters`, I am not a UTF-8 or =
internationalisation expert, but<br>do all alphabets have "capital =
letters" (and should it be "character" rather<br>than =
`letter`)<br></div></div></blockquote><div><br></div><div>There is no =
clear definition of UTF-8 capital letters nor a nice rule to =
apply.</div><div><br></div><div>That could be problem if someone =
proposes tag names in some language that don=E2=80=99t have capital =
letters (chinese ? japanese ?). No sure what to do here. We cannot =
change the =E2=80=9CTagName" type from UTF-8 to ASCII anymore. Maybe we =
could say only latin capital letters ? A lot of languages have a =
latinized version.</div><br><blockquote type=3D"cite"><div><div>### =
Section 3.2.2<br><br>Why not a MUST in `Multiple items SHOULD NOT`? See =
also<br>https://datatracker.ietf.org/doc/statement-iesg-statement-on-clari=
fying-the-use-of-bcp-14-key-words/<br></div></div></blockquote><div><br></=
div><div>This used to be that way but turned back in&nbsp;<a =
href=3D"https://github.com/ietf-wg-cellar/matroska-specification/pull/1030=
">https://github.com/ietf-wg-cellar/matroska-specification/pull/1030</a></=
div><div>After the AD review from Orie&nbsp;<a =
href=3D"https://mailarchive.ietf.org/arch/msg/cellar/4ebLFttRb_I8SFu5yMQSI=
DPuk2E/">https://mailarchive.ietf.org/arch/msg/cellar/4ebLFttRb_I8SFu5yMQS=
IDPuk2E/</a>&nbsp;</div><br><blockquote type=3D"cite"><div><div>### =
Section 3.2.2.2<br><br>A long discussion about the decimal '.' vs. ',', =
but nothing is written in<br>which base the "UTF-8 number" is =
represented. I guess base 10, but let's be<br>specific. I also wonder =
why not using a IEEE binary format was not used<br>(possibly for =
backward compatibility).<br></div></div></blockquote><br><div>These tag =
values often correspond to tags found in other systems like ID3 where =
they are stored as strings. So for compatibility with other systems we =
use strings as well. Newer binary formats like the EBU R128 are stored =
as binary.</div><div><br></div><div>I added some text to mention it=E2=80=99=
s in base 10 in&nbsp;<a =
href=3D"https://github.com/ietf-wg-cellar/matroska-specification/pull/1053=
">https://github.com/ietf-wg-cellar/matroska-specification/pull/1053</a>&n=
bsp;</div><br><blockquote type=3D"cite"><div><div>### Section =
3.3.1<br><br>Should there be a definition or reference for =
`TagChapterUID`? (also for other<br>*UID =
terms).<br></div></div></blockquote><br></div><div>I added some text =
mentioning the ChapterUID which value is used in&nbsp;<a =
href=3D"https://github.com/ietf-wg-cellar/matroska-specification/pull/1054=
">https://github.com/ietf-wg-cellar/matroska-specification/pull/1054</a>&n=
bsp;</div><br></div><div>Thanks again for your =
review.</div><div>Steve</div></body></html>=

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