Man, this is a mess. It appears the whole
root of the problem (which you can see at http://www.w3.org/TR/html401/present/styles.html#specifying-external)
is that HTML 4 decided to create their own “keyword modifier” for values
of the rel= attribute in links. So you can insert the word “alternate”
in front of “stylesheet” (separated by a space, i.e., rel=“alternate
stylesheet”) to designate that it is an alternate stylesheet.
By coming up with their own semantics for how two
independent strings modify each other as values of the rel attribute, they
screwed up everyone else who would simply want it to be able to contain multiple
values.
What were they THINKING???? It completely blows the
regularity and elegance of the architecture.
I don’t know about anyone else, but I feel they have
set such a bad precedent here that I don’t think we or anyone else should
be obliged to follow it. I think we should stick to the rel attribute accepting
multiple space-delimited values, and just accept that if certain of those
values have a relationship to certain other of those values, that’s
application specific.
Otherwise we’d end out completely screwing up the
link model (and XRD 1.0 architecture that is based on it) to accommodate
somebody else’s bad decision.
I propose we make this the lead (and maybe only) topic on
tomorrow’s XRI TC telecon because it’s so important to get this
feedback in now.
=Drummond
From: Eran
Hammer-Lahav [mailto:eran@hueniverse.com]
Sent: Wednesday, April 08, 2009
8:39 AM
To: Eran Hammer-Lahav;
xri@lists.oasis-open.org
Subject: Re: [xri] FW: [link
draft] Changing the model for links
I forgot to mention this
discussion is taking place on the HTTP list ietf-http-wg@w3.org
EHL
On 4/8/09 8:22 AM, "Eran Hammer-Lahav" <eran@hueniverse.com> wrote:
This will have significant impact on XRD. Please read.
EHL
------ Forwarded Message
From: Mark
Nottingham <mnot@mnot.net>
Date: Tue, 7 Apr 2009 16:21:34
-0700
To: <www-tag@w3.org>
Subject: Fwd: [link draft]
Changing the model for links
Begin forwarded message:
> Resent-From: ietf-http-wg@w3.org
> From: Mark Nottingham <mnot@mnot.net>
> Date: 8 April 2009 9:10:58 AM
> To: HTTP Working Group <ietf-http-wg@w3.org>
> Cc: Ian Hickson <ian@hixie.ch>
> Subject: [link draft] Changing the model for links
> Archived-At: <http://www.w3.org/mid/C1CD0848-13F0-4FCF-91FF-52126622C3B8@mnot.net
> >
>
> I've been discussing the link draft with Ian Hickson, who points out
> that in HTML4, there's a difference between
>
> <link rel="stylesheet" href=""a"/>
> <link rel="stylesheet alternate" href=""a"/>
>
> and
>
> <link rel="stylesheet alternate" href=""a/>
>
> (see <http://www.w3.org/TR/html401/present/styles.html#specifying-external
> > for the background of why these are different)
>
> In the current link draft, there isn't any way to express the
> difference between these; the underlying model is
>
> [ context ] ---[ relation type ]---> [ target ]
>
> where 'relation type' is singular.
>
> To accommodate this use, the model would need to be something like
>
> [ context ] ---[ list of relation types ]---> [ target ]
>
> noting that there may be more than one list of relation types
> between any context and target.
>
> Personally, I think that it would be only in pathological cases that
> it would be necessary to know the difference between the two (i.e.,
> real world Web pages will not point to a URI as both a stylesheet
> and as an alternate for themselves, so it's safe to say that even
> the first example above means that "a" is an alternate
stylesheet).
>
> However, it is important for Link to interoperate well with HTML4.
> Also, the HTML5 folks plan to use this model for other purposes
> (e.g., "up up" to indicate a parent of a parent).
>
> The practical impact of making this change is that serialisations of
> links won't be able to collapse multiple relation types between two
> URIs into one link; they'll have to be separate to allow this
> interpretation.
>
> So, for example, if you have link types ['w', 'x', 'y z'] between A
> and B, it will have to be serialised as
>
> Link: <B>; rel="w"
> Link: <B>; rel="x"
> Link: <B>; rel="y z"
>
> in HTTP headers, NOT
>
> Link: <B>; rel="w x y z"
>
> because that's ambiguous.
>
> The alternative is to say that the 'stylesheet alternate'
> combination isn't specific to how it's serialised, but is tied to
> the occurrence of the links. I.e., when both relations are present
> in links between the same resources, these special semantics take
> affect. However, this does seem to directly conflict with the HTML4
> language (see link above), so I don't think doing so is viable.
>
> Comments?
>
> --
> Mark Nottingham http://www.mnot.net/
>
>
--
Mark Nottingham http://www.mnot.net/
------ End of Forwarded Message