Re: [core] Review of draft-ietf-core-multipart-ct-02

"Fossati, Thomas (Nokia - GB/Cambridge)" <thomas.fossati@nokia.com> Wed, 07 November 2018 18:57 UTC

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From: "Fossati, Thomas (Nokia - GB/Cambridge)" <thomas.fossati@nokia.com>
To: Klaus Hartke <hartke@projectcool.de>
CC: Carsten Bormann <cabo@tzi.org>, "core@ietf.org WG" <core@ietf.org>
Thread-Topic: [core] Review of draft-ietf-core-multipart-ct-02
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Date: Wed, 7 Nov 2018 18:57:07 +0000
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Subject: Re: [core] Review of draft-ietf-core-multipart-ct-02
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Hi Klaus,

> I think the draft needs to be much clearer on whether a multipart
> collection is an unordered multiset of representations (which I had
> assumed so far) or an ordered sequence where applications attach
> additional out-of-band meaning to the positions.

The word multiset got me confused.  In my mind a multiset is a set of
(repeatable) elements of the same type.  What do you mean by "unordered
multiset" exactly?

The way I intend multipart-ct, and I think this is also how it's
described in the current draft, is the latter -- i.e. a sequence of 
fields each with its own type.

> Speaking of additional out-of-band meaning, I wonder if there should
> be identifiers in the collection explicitly describing the semantics
> in the interest of self-description.

(see below)

> There are also considerations related to evolving the out-of-band
> information, such as when an application wants to change the meaning
> of a position but continue using the "application/multipart-core"
> content format ID.

Maybe this an example of where the suggestion about freezing a given
multipart-ct into its own content-format comes in handy.  If you want to
change the semantics, you just give it a different c-f.

At this time I wouldn't go down the road of defining a full blown 
container format with all the bells and whistles.  I'd like to see what
we can achieve with this minimalist framework in the first place and
if experience teaches us it's not fit for purpose, we can always make it 
better in a future iteration.

Cheers!