Re: [apps-discuss] [link-relations] Fwd: I-D Action: draft-ohye-canonical-link-relation-00.txt

Frank Ellermann <> Mon, 04 July 2011 21:58 UTC

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From: Frank Ellermann <>
Date: Mon, 04 Jul 2011 23:58:17 +0200
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To: Maile Ohye <>
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Subject: Re: [apps-discuss] [link-relations] Fwd: I-D Action: draft-ohye-canonical-link-relation-00.txt
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On 3 July 2011 03:23, Maile Ohye wrote:

Hi, I've stripped the "link relations expert review list" from the CC:
keeping only the IETF apps list.

> In case this email displays as plain text

Sadly it didn't...  <gd&r>  About "relative canonical URLs":

> We could add a relative URL in the Examples section

Good, thanks.  About "SHOULD vs. MUST":

> We prefer SHOULD NOT for a few reasons.
> 1) If we outlawed multiple canonicals using MUST NOT, we
> would effectively call the HTML invalid. In reality, the
> HTML will still be processed, though it’s likely that
> search engines will ignore both/all rel=canonicals.

If you are very sure that violations of the SHOULD NOT are
only *ignored* I'm fine with it.  But search engines could
also treat violations as some kind of "link farming" and
punish authors for their intended or unintended violations.

In that case authors would be better off with a MUST NOT
clearly indicating that it is their own fault if they get
rel="canonical" wrong -- after all they are not forced to
use rel="canonical".

IOW, if you have "only" a SHOULD NOT for publishers you
might need a corresponding "MUST ignore violations" for
web crawlers.

> Worse, for the cases where somebody might rel=canonical
> to a 404, etc.

Ugh.  A typical use case is a simple site with a mirror,
in that case a 404 should be temporary:  New pages on the
mirror(s) not yet available under their canonical URL, or
old pages deleted under their canonical URL still found
on the mirror(s).

You are right, a MUST NOT does not fly for this scenario.