W3C home > Mailing lists > Public > public-html@w3.org > April 2010

Re: Null change proposal for ISSUE-88 (mark III)

From: Maciej Stachowiak <mjs@apple.com>
Date: Mon, 05 Apr 2010 17:17:54 -0700
Cc: public-html@w3.org
Message-id: <5A9F5E6F-0812-4A2E-9E68-2A0E8B373E98@apple.com>
To: Ian Hickson <ian@hixie.ch>

Updated:
http://dev.w3.org/html5/status/issue-status.html#ISSUE-088

On Apr 3, 2010, at 6:01 PM, Ian Hickson wrote:

>
> ISSUE-88
> ========
>
> SUMMARY
> There is no problem and the proposed remedy is to change nothing.
>
> RATIONALE
> There is no problem.
>
>
> Another change proposal suggests adding a note on the basis that we  
> should
> clarify why the HTTP and pragma declarations are different when it  
> comes
> to values, and how they should be used, suggesting that this is a  
> constant
> source of confusion.
>
> However, no evidence has been provided to suggest that this really  
> is a
> source of confusion.
>
> Furthermore, the suggested note is wrong in practice. The pragma  
> doesn't
> give metadata about the document. The original intent of the <meta
> http-equiv> feature was to provide a way for _servers_ to include  
> data in
> their HTTP headers on a per-file basis; this isn't document-wide  
> metadata
> for user agents, it's for servers. This original intent also doesn't  
> match
> reality; reality is that this pragma sets the default language for
> lang="", which also isn't document-wide metadata for user agents.
>
> Finally, the proffered note does not actually match the associated
> rationale: it doesn't explain why the HTTP and pragma declaration  
> syntaxes
> are different; instead it talks about a "language" attribute.
>
> If there is a "constant source of confusion", then what we need is
> pointers to this confusion, so that text intended specifically to  
> address
> that confusion is included in the spec. It is quite possible that we  
> could
> add lots of explanatory text and explain the situation in detail,  
> but to
> do so we need to know what the confusion is about. As far as I am  
> aware,
> no bug pointing to confusion on this subject and asking for  
> clarification
> has been rejected, which makes using the change proposal process
> inappropriate.
>
>
> The same change proposal also suggests a second change, namely to  
> change
> the syntax to allow multiple comma-separated language codes, even  
> though
> all but the first would be ignored.
>
> User agents vary in their handling of the Content-Language pragma.  
> Some
> user agents support a comma-separated list as meaning (contrary to the
> intent of the Content-Language HTTP header) that the root element  
> and its
> descendants, in the absence of any lang="" attribute, are in multiple
> languages. This seems to contradict the model expected by the :lang
> selector and by the lang="" attribute, which assume that each  
> element has
> a single language.
>
> Other user agents treat the comma as part of the language tag, for  
> example
> treating <meta http-equiv="Content-Language" content="en,fr"> as  
> setting a
> pragma-set default language of "en,fr", which can be matched by a  
> selector
> such as ":lang(en\,fr)", and specifically _not_ by ":lang(en)".
>
> (The specification's UA conformance criteria propose a compromise  
> model
> wherein the user agents aren't required to support multiple  
> languages per
> element, but still interpret the comma correctly, rather than  
> treating it
> as part of the language code.)
>
> Because of the way some legacy UAs handle this pragma, and because the
> behaviour of conforming UAs drops all but the first language, it  
> would be
> ill advised for us to make multiple values conforming. The way to mark
> that a document _uses_ multiple languages in such a way that user  
> agents
> can actually parse and find this information is to use the lang=""
> attribute in the document. Putting multiple values in the pragma would
> fail to handle this according to the proposal.
>
> Another possible use case would be to to have a standard way to say  
> who
> the target audience of the document is, but in practice few people use
> that information on the Web, so it doesn't seem like having a pragma  
> that
> exposes this information would be useful, even if we ignore that the  
> user
> agents are currently required to ignore that information.
>
> Even if there was such a need, this feature would be a bad way to  
> provide
> that information, since it is used in an incompatible way by user  
> agents
> (they use this information to determine processing behaviour -- none  
> of
> the languages are treated as a target audience language hint).
>
> For controlled environments, there are a multitude of options  
> available to
> authors, such as the HTTP header of the same name, <meta name> with  
> custom
> names, microdata, RDFa, out-of-band data, <script> blocks, etc. We  
> don't
> need to use this mechanism for that purpose. Doing so would just  
> confuse
> authors further.
>
> No rationale is given for this second change, so it is hard to  
> evaluate
> what the benefit of making this change would be.
>
>
> Finally, it should be noted that the aforementioned other change  
> proposal
> is self-contradictory. Making the second change (thus making the  
> syntax
> of the pragma the same as its HTTP namesake) would make the  
> rationale for
> the first change (that we should explain the differences between the
> syntax of the pragma and the HTTP header) incorrect.
>
>
> DETAILS
> Change nothing.
>
> IMPACT
>
> POSITIVE EFFECTS
> * Encourages authoring behaviour compatible with both legacy user  
> agents
> and with conforming user agents.
> * Flags uses of the pragma in existing documents that are not being
> reliably processed in existing UAs.
>
> NEGATIVE EFFECTS
> * Flags uses of the pragma in existing documents that are harmless,  
> such
> as "en,en-US". However, evidence suggests that use of the comma is  
> pretty
> rare anyway:
>   http://lists.w3.org/Archives/Public/public-html/2010Apr/0088.html
>
> CONFORMANCE CLASS CHANGES
> None.
>
> RISKS
> It's possible that there is confusion. However, it is easy to handle  
> this
> at a future date when clear evidence of such confusion is found.
>
>
> REFERENCES
> Tests: http://www.hixie.ch/tests/adhoc/html/meta/content-language/
>
> -- 
> Ian Hickson               U+1047E                ) 
> \._.,--....,'``.    fL
> http://ln.hixie.ch/       U+263A                /,   _.. \   _ 
> \  ;`._ ,.
> Things that are impossible just take longer.   `._.-(,_..'-- 
> (,_..'`-.;.'
>
Received on Tuesday, 6 April 2010 00:18:27 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Wednesday, 9 May 2012 00:17:07 GMT