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RE: Last Call: draft-nottingham-http-link-header (Web Linking) to Proposed Standard

From: Ian Hickson <ian@hixie.ch>
Date: Tue, 22 Sep 2009 23:36:02 +0000 (UTC)
To: Eran Hammer-Lahav <eran@hueniverse.com>
Cc: HTTP Working Group <ietf-http-wg@w3.org>
Message-ID: <Pine.LNX.4.62.0909222330380.15471@hixie.dreamhostps.com>
On Wed, 16 Sep 2009, Eran Hammer-Lahav wrote:
> > 
> > I think this basically makes the registry worthless. At least for 
> > HTML5, there are several aspects that we need to have in a 
> > machine-readable fashion for each link type, including:
> > 
> >  - whether the link type is allowed on <link>
> >  - whether the link type is allowed on <a> and <area>
> >  - whether the link type is a hyperlink or references an external
> > resource
> 
> Why?
> 
> The whole point of relation types is that if you see one you don't 
> understand you simply ignore it. It is perfectly reasonable to define a 
> required set so that clients get consistent results using a baseline. 
> But to try and enforce the introduction of new relation types like they 
> were an XML schema goes against the very nature of the mechanism. It's 
> like requiring <A> links to have "value" and be "relevant".

Whether the link type is allowed in the various places in HTML that take 
link types is necessary because otherwise the validator can't say whether 
the link type is being used correctly.

Whether the link type is a hyperlink or references an external resource is 
necessary so that UAs (like wget) can automatically support "save as whole 
page"-like functionality even in the face of relationships they don't 
support. (For example, it would mean wget doesn't need to be revved each 
time browser vendors come up with a new way to hook resource to a 
document, as they did with rel=icon, for instance; it could just update 
itself from the registry).


> > If the link registry isn't going to be providing this, then it's not 
> > really solving the problems for which HTML5 needs a registry.
> 
> It gives HTML5 a consistent semantic meaning without imposing rules on 
> how you utilize that relation. It ensures that developers using multiple 
> technologies don't have to use the same relation type with different 
> semantic meaning which causes mistakes and abuse. Machines don't care 
> about whether a relation type is an English word or a binary array.
> People do. And it would be a significant improvement it we could have a 
> single registry to define what is the meaning / intention of this short 
> relation type.

Those are fine goals, but they're not the goals that led to us creating a 
registry for HTML5.


> For example, I have been using the relation type 'describedby' a lot 
> recently. It has different processing rules for LRDD, XRD, POWDER, etc. 
> But it *means* the same thing.

That seems like two contradictory statements. Surely the meaning of a 
relationship is the processing rules it requires. What else could a link 
type mean?


> > link type be registered with your registry and that the semantics 
> > defined for HTML5 be consistent with those referenced by the 
> > specification given in the registry.
> 
> This would be the right way to handle this. In the future, if many 
> technologies will find it useful to define such custom registries for 
> their own processing rules of relation types, it might make sense to 
> enhance the common registry to hold such information. But given the very 
> different styles of managing such registries (IANA vs. wiki, etc.), it 
> will probably be hard to find a common way to record the information and 
> keep all these different communities happy.

Ok.


> > I would suggest that the IANA host a wiki that anyone can edit.
> 
> That is a horrible idea.
> 
> The registration and semantic meaning of common terms for relation types 
> should be based on wide consensus and not random whims of individuals 
> changing a wiki. We are talking about cross-protocol cross-community 
> registry to establish common basic terminology. Making it lightweight is 
> really not a priority.

If it's harder to register a link type in this registry than in HTML5's, 
then HTML5's will end up a superset, and we will have failed to accomplish 
the goal of avoiding clashes.

-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Tuesday, 22 September 2009 23:29:31 GMT

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