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Re: Link Header draft

From: Roy T. Fielding <fielding@gbiv.com>
Date: Sun, 28 Jan 2007 20:11:21 -0800
Message-Id: <B6BD30FB-2FB1-493E-A897-510E531A06BD@gbiv.com>
Cc: "ietf-http-wg@w3.org Group" <ietf-http-wg@w3.org>
To: Mark Nottingham <mnot@mnot.net>

On Jan 28, 2007, at 3:39 PM, Mark Nottingham wrote:
> The use cases I've heard of so far are with things like OpenID,  
> GRDDL, etc.; there may also be use cases with Atom. I do have some  
> concern about collisions between link relations identifiers in  
> different formats (because <link> in Atom and HTML, for example,  
> are slightly different things).

Umm, what makes them slightly different?

> While Profile acts as a name space for the link relations, I'm not  
> certain it'll be respected. Other approaches that come to mind  
> include;
> 1) Specifying that the name space of the link relations is media  
> type-specific, and have a registry for each.

But, they aren't media type specific -- they are just relations.

> 2) Specifying a whole new header *instead* of Link that allows a  
> URI for the link relation; establish a registry that the relation  
> URI is relative to, independent of media type (still allowing them  
> to use absolute URIs if they like).
> #1 seems workable, but it does require people to register their  
> relations.
> #2 feels OK, *except* that somebody using an Atom link relation,  
> for example, would have to do something like
>    New-Link: <http://example.org/>; rel="atom/self"
> rather than
>    Link: <http://example.org/>; rel="self"
> even though in both cases their content would contain
>   <atom:link href="http://example.org/" rel="self"/>

How about #0:  Specifying the name space as flat, first-come first- 
and standards-track.  I would still deprecate the rev attribute, but I
don't see any real demand for extensible relationship identifiers.

I honestly don't care if two technologies choose the same link relation
name for two different purposes -- that is far less harmful in practice
than two technologies using different names for the same purpose.
Groups that want to ensure some degree of uniqueness can always add
a prefix, like "dc.subject".

Link relations are more like method names than identifiers. We really
don't want people to think that having unique relations is a good thing.

Received on Monday, 29 January 2007 04:11:23 UTC

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