W3C home > Mailing lists > Public > public-html@w3.org > May 2009

Re: HTML interpreter vs. HTML user agent

From: Sam Ruby <rubys@intertwingly.net>
Date: Thu, 28 May 2009 09:41:36 -0400
Message-ID: <4A1E9490.9090208@intertwingly.net>
To: Anne van Kesteren <annevk@opera.com>
CC: Maciej Stachowiak <mjs@apple.com>, "Roy T. Fielding" <fielding@gbiv.com>, Larry Masinter <masinter@adobe.com>, HTML WG <public-html@w3.org>
Anne van Kesteren wrote:
> On Thu, 28 May 2009 15:15:11 +0200, Sam Ruby <rubys@intertwingly.net>
> wrote:
>> A concrete example is feed sniffing, where the operational behavior
>> of feed readers is very different than the operational behavior of
>>  browsers.  If this section is eventually split out, then the issue
>> (with respect to "HTML 5: A vocabulary and associated APIs for HTML
>> and XHTML") goes away.  If, however, it ends up remaining, it needs
>> to be identified clearly as operational behavior of one type of
>> application, and not part of the vocabulary and associated APIs
>> that all applications need to implement.
> Why would feed readers not need to implement that section if they
> want to claim conformance with HTTP and still be compatible with
> legacy content?

I don't understand the "conformance with HTTP" part of the question.  I 
believe that the current spec'ed behavior constitutes "a willful 
violation of the HTTP specification, which requires that the 
Content-Type headers be honored, despite implementation experience 
showing that this is not pratical in many cases.", though I believe that 
that note is not properly placed in the document, and misspells practical.

The actual observed behavior of user agents designed to (primarily) 
process content of a certain media type (either in general, or in the 
specific context) is to make every effort to parse the content according 
to those rules, and only if such rules fail to produce meaningful 
results will they investigate alternatives.

Browsers will first attempt to process content as HTML.
FeedReaders will first attempt to process content as a feed.
Media plays will first attempt to process content as media.

Browsers, when chasing an image tag, will make different assumptions 
than when presented with a raw uri from the chrome.

All are equally "right" or "wrong".

None of this is meant to imply that the behavior that is being settled 
upon by browser manufacturers isn't worth specifying or standardizing.

- Sam Ruby
Received on Thursday, 28 May 2009 13:42:09 UTC

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