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Re: [link draft] Changing the model for links

From: Ian Hickson <ian@hixie.ch>
Date: Wed, 8 Apr 2009 18:37:23 +0000 (UTC)
To: Phil Archer <phil@philarcher.org>, Anne van Kesteren <annevk@opera.com>, Mark Nottingham <mnot@mnot.net>
Cc: HTTP Working Group <ietf-http-wg@w3.org>
Message-ID: <Pine.LNX.4.62.0904081749260.19453@hixie.dreamhostps.com>

Note that in HTML, the following:

   <link href="a.css" rel="stylesheet">
   <link href="b.css" rel="stylesheet">
   <link href="a.css" rel="stylesheet">

...is visibly different to the following case:

   <link href="a.css" rel="stylesheet">
   <link href="b.css" rel="stylesheet">

...and is script-detectably different to the following cases:

   <link href="b.css" rel="stylesheet">
   <link href="a.css" rel="stylesheet">

   <link href="a.css" rel="stylesheet">
   <link href="a.css" rel="stylesheet">
   <link href="b.css" rel="stylesheet">

   <link href="b.css" rel="stylesheet">
   <link href="a.css" rel="stylesheet">
   <link href="a.css" rel="stylesheet">

Similarly, the position of <link> elements relative to other elements 
(e.g. <style>, <script>) and HTTP Link: headers is relevant to behaviour.


On Wed, 8 Apr 2009, Phil Archer wrote:
> 
> For me, the biggest hole in Link in this respect is the lack of support 
> for media types. Not being able to write
> 
> Link <styles1.css> media="handheld" ...
> Link <styles2.css> media="screen" ...
> 
> is a real downer but I know this has been raised before.

Yeah, it seems like we would want provide attributes like media=""... 
HTML5 introduces sizes="" for one rel-type, if HTML is to use the same 
model so that you can set favicons from Link headers also, then we'd have 
to include this too.


On Wed, 8 Apr 2009, Mark Nottingham wrote:
> 
> What's the status of "up up", etc. in HTML5 these days?

Tentative. (The section is marked "last call for comments".)

I think it would be very unfortunate to lost this feature just because the 
underlying model can't describe it, though.


> Also, has testing been done around UAs with regard to serialisation in 
> HTML? I.e., which of these qualify as an alternate stylesheet according 
> to implementations?
> 
> <link rel="alternate stylesheet" href="a"/>
> <link rel="stylesheet alternate" href="a"/>
> <link rel="stylesheet" href="a"/><link rel="alternate" href="a"/>

The first two. I don't know of any software that does special things with 
rel="" for serialisation, so I haven't tested anything on that side.


> Again, if "alternate stylesheet" is grandfathered in and "up up" is 
> supported by saying that all forms that result in two links to the same 
> target with 'up' as the relation, it's a lot easier to get there.

I don't think that would really work, I think it would be quite plausible 
for example for pages to have breadcrumb links at the top and bottom of a 
page.

Also, note that as defined in HTML5 the breadcrumb mechanism is scoped to 
the current paragraph. This is something else that might be hard to 
express in a common data model.


On Wed, 8 Apr 2009, Mark Nottingham wrote:
> 
> So, I'm very interested in whether 'up up' is a good idea, whose idea it 
> is, who wants to implement it, and who already has.
> 
> More to the point, does anybody really need 'up up up up up up up', 
> which is what this implies?

Link types in general aren't that widely used, sadly. The idea with the 
new rel-up/rel-index feature in HTML5 is to enable breadcrumbs to be 
expressed; quite a lot of people have asked for ways to do this. I don't 
know if what we have now is the best way to do it.

-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Wednesday, 8 April 2009 18:38:06 GMT

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