Re: FW: issue-dbooth-4f: Sec 4, base IRI of an element

On Fri, 2007-06-15 at 11:53 +0100, Jeremy Carroll wrote:
> Summary:
> 
> two possible suggested changes:
> 
> 1) change the normative text from
> "the base IRI of E" to "the base IRI of N"
> in the specific rule
> http://www.w3.org/2004/01/rdxh/spec#rule_tlrel
> or

I don't think this would work, since E is the link element itself (where
the @href and @rel attributes are defined) and N is the root node.  XML
Base gives a mechanism for assigning a base IRI "in context" (i.e., from
the link element, to the head element, and up to the html root element).
The XHTML Base module provides a  universal base URI for resolving
relative references.  Why would we want to remove the context? It
doesn't seem in the spirit of XML Base.

> 2) change the informative text, after the rule from:
> "Note that the base IRI of an element node in an XHTML document may be 
> influenced by factors such as a base element[HTML4] Retrieval 
> URIRFC3986, etc. See test cases such as htmlbase1 for further 
> clarification."
> to
> "Note that the base IRI of an element node in an XHTML document
> is the base IRI of the document and may be influenced by factors such as 
> a base element[HTML4] Retrieval URIRFC3986, etc. See test cases such as 
> htmlbase1 for further clarification."
> 
> (In case 1, the informative text would need a small tweak too)
> (my preference is (2))

If we follow John's earlier [1] assumption (which is the same as mine)
about XHTML Base:

"Note that I am assuming that in XHTML, xml:base *is*
supported, since XHTML is a proper XML dialect."

Then wouldn't that be in conflict with the suggested change?

> But in section 4, XHTML does not implement XML Base, and hence in XHTML 
> documents XML Base is illegal, and a user-agent (including a GRDDL aware 
> agent) should either flag the error or ignore it.

Is this really the case? If XHTML doesn't support xml:base then is it an
XML dialect or independent markup with an XML serialization?  If it is
the former, *should* it really have application/xhtml+xml as its media
type?

> Hence, the wording in
> http://www.w3.org/2004/01/rdxh/spec#rule_tlrel
> "the base IRI of E"
> is slightly misleading, and might result in interoperability failures 
> with a document in the xhtml namespace, that does include an xml:base.

It only fails if there is an xml:base in an XHTML document, which
*seems* to be an undefined combination.

> To some extent this is a GIGO problem.
> If someone mistakenly believes that XML Base is supported by XHTML then 
> they are likely to find different implementations behaving differently. 
> It is, in general, reasonable for a generic XML processor to assume that 
> if the document author has used xml:base then it has been used legally, 
> and not reasonable to expect a generic XML processor to know which 
> document formats support xml:base and which don't and to flag errors of 
> the form, "xml:base has been used inappropriately".

I agree.

> Section 4, which is specifically about XHTML should not. However, the 
> normative rule is written in greater generality (i.e. any XPath node set 
> with a metadata profile, although metadata profiles are only defined for 
> XHTML)
> 
> I think my preference, at this stage, would be to tweak the informative 
> text. I fully expect interoperability failures in this case, but that is 
> because of the confusing state of when xml:base can and cannot be used, 
> and that is not within this group's control or remit.

The only issue is when used in combination with an XHTML Base.  It is
hard to know what to tweak to adequately describe an undefined
situation.  At least, stating that the relative URI resolution happens
WRT the immediate context allows processors which honor xml:base in all
cases to do so.

> Whether this issue should be further called out in the (possible) new 
> base appendix, I am unclear. I think it is more important that at least 
> some implementations flag the error (using xml:base inside an HTML doc) 
> than the exact wording of the spec.

Perhaps the base appendix should highlight why use of xml:base with
XHTML Base is undefined, but be explicit about other scenarios and their
relationships with XML Base, XHTML Base, and RFC 3986?

[1]http://lists.w3.org/Archives/Public/public-grddl-wg/2007Jun/0083.html
-- 
Chimezie Ogbuji
Lead Systems Analyst
Thoracic and Cardiovascular Surgery
Cleveland Clinic Foundation
9500 Euclid Avenue/ W26
Cleveland, Ohio 44195
Office: (216)444-8593
ogbujic@ccf.org


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Received on Friday, 15 June 2007 13:40:02 UTC