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RE: Feedback for draft-nottingham-http-link-header-03

From: Drummond Reed <drummond.reed@cordance.net>
Date: Fri, 5 Dec 2008 21:53:25 -0800
To: "'Ian Hickson'" <ian@hixie.ch>, "'Phil Archer'" <phil@philarcher.org>
Cc: <ietf-http-wg@w3.org>, "'Eran Hammer-Lahav'" <eran@hueniverse.com>, "'Mark Nottingham'" <mnot@mnot.net>
Message-ID: <24268E32EB5F4B8C91160A658FEC14AA@ELROND>

> > On Wed, 3 Dec 2008, Phil Archer wrote:
> >
> > HTML 5 has dropped rev for the link element and if the tide is against
> > keeping rev in HTTP Link then the impression being given might be that
> > rev is deprecated everywhere.
>
> On Friday, 5 Dec 2008, Ian Hickson wrote:
> 
> Eran asked me to chime in here to give some background on why HTML5 drops
> the "rev" attribute.
> 
> It basically boils down to reducing author confusion. As can be seen from
> this thread, even people quite familiar with Web standards and semantics
> have trouble defining exactly what it means. We did some research and
> found a quite startling situation: the most common value for rev="" in the
> HTML pages we examined was rev="made", which is equivalent to
> rel="author", and the second most common value was rev="stylesheet", which
> is a typo. The remaining values were so too rare to examine. Further
> evidence that there was confusion: rel="made" was a common rel="" value,
> though it is likely that in most cases it should have been rev="made" or
> rel="author".
> 
> What we concluded from this was that despite the feature (rev="") being
> available for a decade or more, authors don't need it, and don't
> understand it.

It seems like a reasonable conclusion relative to HTML authoring.

> We can help authors by making this that they usually misuse invalid,
> because then the validators will catch their errors. (Right now, an HTML4
> validator can't strictly say that rev="stylesheet" was an error, and so
> the error goes undetected even by authors using QA tools.)
> 
> The data was published here:
>    http://code.google.com/webstats/2005-12/linkrels.html
> 
> (More recent but unpublished studies have shown similar results in larger
> and more recent datasets.)
> 
> The above was weighed against the (currently mostly theoretical) need for
> rev="" in various fields, such as RDFa, some Microformats, and so on, but
> on the balance we decided that the immediate help to authors was worth
> more to authors and users than these use cases. Helping with this was the
> realisation that rel="" values could always be minted in a way that was
> equivalent to rev="". For example, if someone had rel="foobar" and really
> wanted rev="foobar" to be available too, they could instead just define
> and use rel="rev-foobar".

Some recent feedback on Link Header highlights a serious issue with that
workaround. Even if HTML5 drops "rev", it doesn't change the semantics
established in HTML4, RDFa, and other uses that "rel" and "rev" assert
outbound and inbound links, respectively. So to start saying that _some_
uses of "rel" can assert inbound links by inserting special semantics _into
the value_ of the attribute would appear to invite a real semantic mess.

Much better to either: a) drop support for "rev" but leave "rel"
unambiguously asserting outbound links, or b) define a whole new attribute
that explicitly takes link directionality semantics out of the attribute
definition and puts them into the attribute value.

=Drummond 
Received on Saturday, 6 December 2008 05:54:12 GMT

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