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ACTION-983: same-document reference

From: Francois Daoust <fd@w3.org>
Date: Mon, 22 Jun 2009 17:42:33 +0200
Message-ID: <4A3FA669.2030300@w3.org>
To: Mobile Web Best Practices Working Group WG <public-bpwg@w3.org>
Hi,

Discussion on "same-document" references started a long time ago when 
Dom managed to have the group follow his unwise principle that a URI 
always represents the resource and not a given representation of the 
resource. This led to the production of a very smart algorithm in the 
last call version of the guidelines. This was shortly followed by last 
call comment LC-2009 [1]. The comment pointed us to section 4.4 of 
RFC3986 "Uniform Resource Identifier (URI): Generic Syntax" [2] that 
defines the concept of "same-document reference".

In particular, it does say:
[[
    When a same-document reference is dereferenced for a retrieval
    action, the target of that reference is defined to be within the same
    entity (representation, document, or message) as the reference;
    therefore, a dereference should not result in a new retrieval action.
]]
... meaning that a URI that appears in the representation of a resource 
and that happens to be a same-document reference represents the 
representation of the resource, and not the resource itself.

We blamed Dom. We still had extensive discussions on the topic such as 
in [3], in particular because it also connects with the ("Oh no!", the 
Lemming says and explodes) ISSUE-222 [4] and the TAG Finding On Linking 
Alternative Representations To Enable Discovery And Publishing [5]. The 
thing is the theory does not entirely match practice and most (all?) 
browsers do not correctly handle the case when you want to use a 
canonical URI for bookmarking purpose. Plus there is no true way to 
define a URI as the canonical URI for a set of representations [6].

Whilst this is true, it is not directly related to the definition of a 
"same-document reference" and does not change its definition either. In 
short, unless we have good reasons not to, we should stick to the 
definition of the above-mentioned RFC, and this is exactly what Appendix 
G.1.4.2 [7] does.

However, the first bullet point in section 4.2.9 [8] restricts the 
possibility of a "Same Document reference" to an empty href attribute. 
For consistency, the text should rather be:
[[
  the content is HTML and contains <link rel="alternate" 
media="handheld" href="[same-ref]"/> where [same-ref] is a "Same 
Document reference" as defined in RFC 3986 section 4.4 [REF]. In 
particular, an empty href attribute is a "Same Document Reference".
]]

Francois.


[1] 
http://www.w3.org/2006/02/lc-comments-tracker/37584/WD-ct-guidelines-20080801/2009
[2] http://tools.ietf.org/html/rfc3986.html#section-4.4
[3] http://lists.w3.org/Archives/Public/public-bpwg-ct/2008Sep/0027.html
[4] http://www.w3.org/2005/MWI/BPWG/Group/track/issues/222
[5] http://www.w3.org/2001/tag/doc/alternatives-discovery.html
[6] http://lists.w3.org/Archives/Public/public-bpwg/2009Feb/0096.html
[7] 
http://www.w3.org/2005/MWI/BPWG/Group/TaskForces/CT/editors-drafts/Guidelines/090622#sec-use-of-link-element
[8] 
http://www.w3.org/2005/MWI/BPWG/Group/TaskForces/CT/editors-drafts/Guidelines/090622#sec-proxy-decision-to-transform
Received on Monday, 22 June 2009 15:43:09 UTC

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