- From: Mark Nottingham <mnot@mnot.net>
- Date: Wed, 3 Dec 2008 21:39:05 +1100
- To: Phil Archer <phil@philarcher.org>
- Cc: "ietf-http-wg@w3.org Group" <ietf-http-wg@w3.org>, Eran Hammer-Lahav <eran@hueniverse.com>, Drummond Reed <drummond.reed@cordance.net>
I think the key is to define the semantics of rel vs. rev well enough that a relation doesn't necessarily have to say something about them, but that it still can without conflicting. Yes, that's a fine line to walk. On 03/12/2008, at 8:53 PM, Phil Archer wrote: > I'd just like to jump in on one point: > > Eran Hammer-Lahav wrote: > [..] >>>>> Each link-value MUST have at least one "rel" or "rev" parameter >>>>> whose >>>>> value indicates the relation type. If the "rel" parameter is >>> used, >>>>> it indicates that the link's direction for that relation type is >>>>> outbound; if the "rev" parameter is used, the given relation >>> type's >>>>> direction is inbound. >>>> Is 'rev' considered as authoritative as 'rel' (as in, 'type' is >>>> non- >>>> authoritative, just a hint)? Forward looking links using 'rel' are >>>> clearly authoritative as they indicate the view-point of the >>>> resource, which has the authority to declare its own perceive links >>>> to other resources. However, 'rev' can go both ways. It seems to be >>>> semantically equivalent to an identical 'rel' coming from the >>>> linked >>>> resource. For example: >>>> >>>> Resource A: Link: <http://example.com/b>; rel="friend" >>>> Resource B: Link: <http://example.com/a>; rev="friend" >>>> >>>> If the two are semantically identical, 'rev' must be non- >>>> authoritative as it serves as a hint as to what another resource >>>> view the relationship as: "A declares B to be <<its friend>>, B >>>> hints that A <<declares B its friend>>". However, if 'rev' is meant >>>> to be authoritative, the two links above cannot be semantically the >>>> same, as they read: "A declares B to be <<its friend>>, B declares >>>> that A <<consider it a friend>>". The question is, is 'rev' simply >>>> an implied 'rel' from the other direction (and so, non- >>>> authoritative), or 'rev' is a reverse "opinion" of 'rel' which is >>>> completely relative to the resource regardless of any actual 'rel' >>>> from the other direction (and so, authoritative). >>> This draft isn't attempting to establish a framework for semantics >>> or >>> trust, and I'm tempted to take out anything that might imply this... >> I think at a minimum it needs to clearly define the relationship >> between 'rel' and 'rev'. This is why I liked it better when 'rev' >> was dropped. If you only have 'rel', you can express 'rev' with >> another 'rel' value, and that will solve my issue. If you keep >> both, I can't see how you can avoid explaining their relationship >> to one another as listed in the example above. > > I just wrote out an argument for why I felt it was important to keep > rev... and realised that my own arguments convinced me that it > probably isn't needed for HTTP Link after all. The arguments over > the relative authority and semantics of rel and rev links is pretty > compelling. > > And yet, and yet... I would still be concerned to see it go because > it is *really* useful in RDFa. 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. > Even though that is not what is being said or implied here, it could > lead to future confusion. > > Phil. > > -- > > Phil Archer > w. http://philarcher.org/ -- Mark Nottingham http://www.mnot.net/
Received on Wednesday, 3 December 2008 10:39:44 UTC