W3C home > Mailing lists > Public > www-tag@w3.org > December 2002

Re: Content negotiation issues (was XInclude)

From: Jeremy Dunck <ralinon@hotmail.com>
Date: Mon, 30 Dec 2002 17:29:59 -0600
To: simonstl@simonstl.com, www-tag@w3.org
Message-ID: <BAY1-F149XPMzJ09Z6e000208a7@hotmail.com>

>From: "Simon St.Laurent" <simonstl@simonstl.com>
A couple niggles:
>
<snip>
>There seems to be a general issue with XML specifications and
>content-negotiation.  While the HTML object element includes a type
>attribute that permits such negotiation [1], as do some other aspects of

The type attribute included in HTML is not used for content negotiation, in 
the strict sense.  That is, the value of this attribute is supposed to allow 
the user agent to decide whether to retrieve a resource at all.

From the spec:
"
This attribute specifies the content type for the data specified by data. 
This attribute is optional but recommended when datais specified since it 
allows the user agent to avoid loading information for unsupported content 
types. If the value of this attribute differs from the HTTP Content-Type 
returned by the server when the object is retrieved, the HTTP Content-Type 
takes precedence.
"

My point is that the server -still- maintains control over the actual MIME 
type of representation returned.

>HTML, SMIL, and SVG, most of the XML-based specifications - including
>XInclude and XLink - seem to take a "we provide the URI reference, you
>do with it as you like" approach.

I am not so sure this is a bad way to go.  In my opinion, the server must 
maintain control of the type of the representation returned.  However, that 
doesn't preclude a client from using it in some other way (And I'm pretty 
sure I heard this argument here a couple days ago).  For example, an XML doc 
which is included might be treated as text in order to drop it into CDATA, 
or somesuch.

<snip>
>While these principle don't explicitly reject the more explicit
>specification approach of HTML etc., the combination of their (generally
>worthwhile) conservatism and the lack of specification of any explicit
>mechanisms in the XML specifications to handle content-negotiation
>should effectively provide a straitjacket for conscientious XML
>developers.

I'm not sure I followed that.  Is this derived from the misunderstanding 
that the HTML type attribute is used in content negotiation?

<snip>



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Received on Monday, 30 December 2002 18:30:36 GMT

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