Re: Request to register "identifier" relation type

Herbert Van de Sompel <> Wed, 09 August 2017 14:35 UTC

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From: Herbert Van de Sompel <>
Date: Wed, 9 Aug 2017 16:35:02 +0200
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Subject: Re: Request to register "identifier" relation type
To: link-relations <>
Cc: Peter Williams <>, Geoffrey Bilder <>, Michael Nelson <>, Simeon Warner <>, "John A. Kunze" <>, Ed Summers <>, Herbert Van de Sompel <>
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On Sat, Aug 5, 2017 at 2:56 PM, Herbert Van de Sompel <>

> On Aug 5, 2017, at 13:59, Ed Summers <> wrote:
> >
> >> On Aug 5, 2017, at 3:38 AM, Herbert Van de Sompel <>
> wrote:
> >>
> > I wonder if rather than adding another link relation to the mix if the
> HTML folks would be willing to update rel=bookmark

to allow for usage with <link> which ought to make it amenable to use in an
> HTTP header as some other HTML relations are (e.g. alternate). The
> semantics of bookmark speak directly to the issue of persistence that your
> I-D seems to be addressing.
> >
> Our I-D acknowledges that the semantics of "identifier" are similar to
> "bookmark". But "bookmark" is explicitly not allowed in <link> (and hence
> Link). One has to assume there were/are reasons for that choice because
> other rel types declared in HTML can be used in <link>.
Update: Since, the above mail exchange regarding the suggested use of
"bookmark" the following actions were taken:

* On August 5, Ed Summers posted a question regarding applying "bookmark"
to <link> to the WHATWG list, see
ves/Public/public-whatwg-archive/2017Aug/0001.html. There are no responses
to this post, so far.

* On August 9, Ed Summer posted a similar question to WHATWG/HTML GitHub,
see There is a reaction from
@annevk who (1) speculates that the reason "bookmark" is not to be used
with <link> might be in order not to overlap with "canonical" (2) suggests
the use of "canonical" :-)

* Michael Nelson has further explored "bookmark" and has confirmed that
there effectively is a reason for not allowing "bookmark" in <link>. It is
related to its target use case: surfacing a link for content contained in a
*part* of a page. Hence, Michael concludes that making "bookmark" usable
with <link> will most likely not happen. @annevk's GitHub response does not
seem to contradict that. Michael based his findings on studying and He
may write another blog post about this, but, for now, here's how he
explained on Twitter

As a summary, thus far, of these discussions:

* We have further explained, in a special-purpose blog post, that
"canonical" is not applicable for the use cases we describe in our I-D.

* We have shown that there is a reason why "bookmark" is not usable with
<link>. While the relation type name suggests it has the appropriate
semantics intended by "identifier", its intended use is surfacing a link
for content contained in a *part* of a page. That's not the intention of
"identifier", which is about surfacing another URI (for the purpose of
referencing) for an entire resource.

We agree with Ed Summers that we need to use the web we have, where
possible. To that end, we had included an analysis in our I-D explaining
why certain existing rel types are not applicable. Based on the
discussions, here, we will be able to further clarify that analysis in a
next iteration of our I-D. But the analysis will still reach the conclusion
that these existing relation types are not applicable. As such, we also
reconfirm our request to register "identifier".



Herbert Van de Sompel
Digital Library Research & Prototyping
Los Alamos National Laboratory, Research Library