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Re: Review of Authoritative Metadata

From: Roy T. Fielding <fielding@gbiv.com>
Date: Mon, 27 Mar 2006 13:48:44 -0800
Message-Id: <97549A67-F4E5-4938-962A-6B754EC9B710@gbiv.com>
Cc: <www-tag@w3.org>
To: "Rice, Ed (ProCurve)" <ed.rice@hp.com>

On Mar 27, 2006, at 12:23 PM, Rice, Ed (ProCurve) wrote:
> Roy/TAG,
> Some thoughts on the latest Authoritative Metadata paper at
> http://www.w3.org/2001/tag/doc/mime-respect-20060307
> 1 - In Section 2 you state "For Web architecture, a design choice has
> been made that metadata received in an encapsulating container MUST be
> considered authoritative.."
> 	Question:  Is this a 'design choice' or a 'determination'?  A
> design choice seems to leave it open to more interpretation than a TAG
> determination..

I'm not sure that I detect any difference between those terms, but in
any case the choice was made back in the 1992-93 timeframe (pre-TAG).
The TAG is simply reiterating that choice for the reasons given.

> 2 - 3.3 external reference metadata is least authoritative.
> 	Question: In deference to most html, doc types I would agree.
> Is the same true however to xml?  Is the WSDL least authoritative in
> regards to a SOAP message?  I believe by definition the WSDL is THE
> authoritative source as to the format of the doc when it comes to web
> services (please correct me if I'm wrong).  Clearly in this  
> instance the
> WSDL would specify xml, but the element structure/types within the xml
> are also defined in the meta data of the WSDL.  I would also think the
> same applies to an xml/xsd relationship where the xsd is the
> authoritative source regarding the structure of the xml?

I don't think so.  WSDL may define the rules for constructing a SOAP
message, but the recipient has to read the message to determine
what the message means.  WSDL is OOB data that isn't even relevant
unless the SOAP metadata references the WSDL, in which case the SOAP
metadata is authoritative because that is where the decision is made.

I think you are confusing authoritative with definitive.  The WSDL is
definitive once it is referenced by the SOAP message, but the SOAP
message is being authoritative when it references the WSDL definition.
If the SOAP message is well-formed but incorrect, then the fact that
the message references the WSDL allows the processor to determine
that the message is incorrect.  It does not change the meaning of the
message.  This would be in contrast to a SOAP message that doesn't
reference the WSDL at all -- the request may succeed or fail, but the
message is assumed correct because there is nothing (aside from the
SOAP messaging format) to measure its correctness against.

In any case, SOAP messaging has no connection to the Web, AFAICT,
and certainly doesn't adhere to Web architecture, so I have a hard
time caring whether or not it fits the finding (even when it does).

Received on Monday, 27 March 2006 21:49:08 UTC

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