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FW: Proposed positive text for XML Base

From: Jonathan Marsh <jmarsh@microsoft.com>
Date: Wed, 17 Oct 2001 16:22:04 -0700
Message-ID: <330564469BFEC046B84E591EB3D4D59C038E4025@red-msg-08.redmond.corp.microsoft.com>
To: <xml-dist-app@w3.org>
Cc: "Henrik Frystyk Nielsen" <henrikn@microsoft.com>, "Paul Cotton" <pcotton@microsoft.com>
Henrik and Paul consulted with me on this issue, in my role as editor of the XML Base Recommendation, resulting in an updated proposal based on David Orchard's text.  Although I am a member of the XML Core WG, and believe the text below is consistent with the feedback the Core WG provided on this issue, I do not supply this text under the aegis of the Core WG.  I hope that this proposal is helpful to the XP WG in considering this issue.


BASE URI's and Relative URI Resolution
--------------------------------------
This version of the SOAP specification supports the W3C XML Base Recommendation. An xml:base attribute information item MAY appear on any of the element information items defined in this specification.  This specification does not make use of URI References, only absolute URIs, so xml:base attributes will not affect the behavior of the SOAP envelope itself.  Relative URI values (such as for the SOAP-ENV:EncodingStyle attribute) are not recognized as matching the absolute URI values mandated by this specification.

The XML Base specification provides a standard base URI for the contents of the SOAP-ENV:Body or other header entries.  Specifications for particular applications of SOAP, as well as specifications for transport bindings, header entries and/or body entries MAY define the base URI of the SOAP message interpretation of relative URI's within such body or entries additionally.  When such mechanisms depend upon the base URI of a higher context, such as the document, they SHOULD be given the base URI of the nearest ancestor SOAP envelope element instead.  In the absence of such additional specifications, the resolution of relative URI's appearing within the contents of a body or other header entry is defined by XML Base.  It is not recommended that new specifications invent new mechanisms for adjusting the base URI, since these mechanisms will be in conflict with the [base URI] infoset property, which only recognizes XML Base.

Namespace declarations for the namespaces used in this specification (such as http://www.w3.org/2001/06/soap-envelope) MUST be provided as absolute URI's. Element or attribute names qualified with relative URI namespaces are not recognized as matching the absolute names mandated by this specification."


Rationale:
----------
The simplest reading of SOAP 1.2 does not allow relative URIs (specifically URI References) in any of its attributes.  Making such a change requires positive motivation.  Use cases demonstrating the value of relative URIs in each circumstance should be found before considering a change.  XML Base is a tool for interpreting URI References, and its availability does not mean that all URIs benefit from becoming URI References.

Here is how the proposal above supports the various flavors of base URI calculation:

1) Some payloads will support XML Base.  For example, the payload1 grammar allows xml:base attributes and recognizes XML Base:

<s:envelope>
  <s:body xml:base="http://www.example.com">
    <payload1 ref="test.xml" xml:base="/dir/">
      This grammar honors XML Base.
      The ref is http://www.example.com/dir/test.xml.
    </payload1>
  </s:body>
</s:envelope>

The proposal is optimized for this case.  The [base URI] property of the infoset reliably allows relative references to be resolved.

2) Payloads that don't allow xml:base attributes, and assume the document URI is the base, have a clean interaction with the envelope.  Relative URIs must be interpreted relative to the base URI of the SOAP envelope element.  For example, the payload2 grammar does not recognize XML Base or allow xml:base attributes:

<s:envelope>
  <s:body xml:base="http://www.example.com">
    <payload2 ref="test.xml">
      This grammar does not honor XML Base, or allow xml:base attributes.  
      The ref is http://www.example.com/test.xml, not <message base>/test.xml.
    </payload1>
  </s:body>
</s:envelope>

3) Payloads that provide a different mechanism for determining XML Base, also have a clean interface with the envelope:

<s:envelope>
  <s:body xml:base="http://www.example.com">
    <xhtml:html>
      <xhtml:base href="/dir/"/>
      <xhtml:body>
        <xhtml:a href="test.xml"/>
        The href is http://www.example.org/dir/test.xml.
      </xhtml:body>
    </xhtml:html>
  </s:body>
</s:envelope>

Note that relative URIs for the base are not actually allowed in XHTML.  Note that the [base URI] property of the <xhtml:a> element is http://www.example.com, although an XHTML application would instead treat it as http://www.example.com/dir/.  New specifications should avoid specifying such mechanisms, because processing the relative URI using a generic processor rather than an application-specific processor will provide different results.


-----Original Message-----
From: David Orchard [mailto:david.orchard@bea.com] 
Sent: Friday, October 05, 2001 17:17
To: xml-dist-app@w3.org
Subject: Proposed positive text for XML Base
I took Noah's excellent wording[1] and semantically NOTed it.  My attempt follows.  Please note that this wording defines that relative URI's ARE interpreted according to xml:base, therefore implementations must support xml:base.  It seems to me that an application that doesn't support xml:base but supports relative URIs is an undefined state. 

BASE URI's and Relative URI Resolution
-------------------------------------- 
"This version of the SOAP specification supports the W3C XML Base Recommendation. The xml:base attribute MAY appear on the SOAP-ENV:Envelope, SOAP-ENV:Body, SOAP-ENV:Header, or SOAP-ENV:Fault elements. 

The XML Base specification provides a standard Base URI for the contents of the SOAP-ENV:Body or other header entries.  Specifications for particular applications of SOAP, as well as specifications for transport bindings, header entries and/or body entries MAY define the interpretation of relative URI's within such body or entries additionally. In the absence of such additional specifications, the resolution of relative URI's appearing within the contents of a body or other header entry is defined by XML Base. 

Relative URI's MAY be used as values for attributes or elements (such as SOAP-ENV:Actor, SOAP-ENV:EncodingStyle) defined by this specification; if such values are used, their resolution to absolute URI's is defined according to the XML Base Recommendation. 

Namespace declarations for the namespaces used in this specification (such as http://www.w3.org/2001/06/soap-envelope) MUST be provided as absolute URI's. Element or attribute names qualified with relative URI namespaces are not recognized as matching the absolute names mandated by this specification." 

Cheers,
Dave Orchard

[1] http://lists.w3.org/Archives/Public/xml-dist-app/2001Aug/0268.html 
Received on Wednesday, 17 October 2001 19:23:41 GMT

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