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Re: Feedback for draft-nottingham-http-link-header-03

From: Mark Nottingham <mnot@mnot.net>
Date: Wed, 10 Dec 2008 10:35:31 +1100
Cc: "Drummond Reed" <drummond.reed@cordance.net>, "'HTTP Working Group'" <ietf-http-wg@w3.org>, "'Ian Hickson'" <ian@hixie.ch>
Message-Id: <199041C6-2D67-40A2-9684-2E9CE53EC2DB@mnot.net>
To: "Roy T. Fielding" <fielding@gbiv.com>

On 10/12/2008, at 8:37 AM, Roy T. Fielding wrote:

> On Dec 9, 2008, at 4:18 AM, Mark Nottingham wrote:
>> That's an extraordinarily subtle distinction (and I still haven't  
>> thought
>> through its impact if we act upon it).
> Well, <http://tools.ietf.org/html/draft-nottingham-http-link- 
> header-03> says
>   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.
> which is wrong.  The distinction isn't subtle if you think about what
> Link defines and how agents are supposed to act on that information.
> We should remove the mistaken usage of "outbound" and "inbound" and
> the definition of rev should be in section 4 (and deprecated because
> experience has shown that reversing semantics is less understandable
> by people than choosing inverse relation names).
>> Is your preference still to keep rev out of the spec?
> No, my preference is to leave it in but deprecate its use.

I think I agree, as long as we can illustrate it well.

The RDF folks should note, though, that REV isn't the link they're  
looking for, AIUI.

> Also, I note the following:
>   If the relation-type is a relative URI, its base URI MUST be
>   considered to be "http://www.iana.org/assignments/relation/", and  
> the
>   corresponding value MUST be present in the link relation registry.
> A MUST here requires that implementations look-up the registry to
> confirm the entry.  Nobody wants that.  There is no need for these
> requirements -- the base is a statement of fact, and the semantics
> are necessarily concluded from that fact.  It should just say:
>   The URI-reference(s) within relation-type are parsed relative to
>   the base URI of <http://www.iana.org/assignments/relation/>.
>   A relation-type value that is not an absolute URI [RFC3986] is
>   therefore presumed to be a relative reference to the corresponding
>   relation within the IANA relation registry [cite].  If no such
>   registered relation exists or the reference is malformed, then
>   the relation is undefined.  Implementations SHOULD ignore relation
>   names that they do not understand or have no need to process.


I'll start work on -04.

Mark Nottingham     http://www.mnot.net/
Received on Tuesday, 9 December 2008 23:36:15 UTC

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