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RE: NEW ISSUE: The framework specification should enable usage of xml:id

From: Asir Vedamuthu <asirveda@microsoft.com>
Date: Fri, 11 Aug 2006 16:54:41 -0700
Message-ID: <4DF3D07B9910264B9470DA1F811D1A950B260FAF@RED-MSG-43.redmond.corp.microsoft.com>
To: "Yalcinalp, Umit" <umit.yalcinalp@sap.com>, <public-ws-policy@w3.org>

> We could also add a note in the framework/primer when it is not 
> desirable to use xml:id but rely on wsu:id

Good point.

The xml:id Version 1.0 specification says, 'The Canonical XML Version 1.0 specification describes a process whereby attributes in the xml: namespace are inherited in a canonicalized document. While this produces a reasonable result with xml:lang or xml:space attributes, processing xml:id attributes in this way is likely to produce documents that contain xml:id errors, specifically xml:id attribute values that are not unique.'[1]

An illustrative description of the above technical issue can be found in [2]. The XML Core Working Group is chartered [3] to produce a new version of Canonical XML to address this inconsistency.

'XML Signature Syntax and Processing' requires implementations to support C14N 1.0 [4]. C14N 1.0 is widely supported [5] and used. In many cases, users only have access to C14N 1.0 support.

If the WG wants to adopt the xml:id attribute in addition to the wsu:Id attribute, we suggest amending the proposal to include the following note of caution to Section 4.2:

"The use of xml:id attribute in conjunction with Canonical XML 1.0 is inappropriate as described in Appendix C of xml:id Version 1.0 [XMLID] and thus this combination must be avoided (see [C14NNOTE]). For example, a policy expression identified using xml:id attribute should not be signed using XML Digital Signature when Canonical XML 1.0 is being used as the canonicalization method." Where, C14NNOTE is a non-normative reference to [2].

[1] http://www.w3.org/TR/2005/REC-xml-id-20050909/#impact
[2] http://www.w3.org/2006/04/c14n-note/c14n-note.html#S3
[3] http://www.w3.org/2005/02/xml-core-wg-charter.html#deliverables
[4] http://www.w3.org/TR/2002/REC-xmldsig-core-20020212/#sec-c14nAlg
[5] http://www.w3.org/Signature/2001/04/05-xmldsig-interop.html 
    http://www.w3.org/Signature/2000/10/10-c14n-interop.html

Regards,

Asir S Vedamuthu
Microsoft Corporation

________________________________________
From: public-ws-policy-request@w3.org [mailto:public-ws-policy-request@w3.org] On Behalf Of Yalcinalp, Umit
Sent: Tuesday, July 25, 2006 1:54 PM
To: public-ws-policy@w3.org
Subject: NEW ISSUE: The framework specification should enable usage of xml:id


Title: The framework specification should also enable the usage of xml:id 
Description: 
The WS-Policy Framework specification uses wsu:id element to designate identification for elements[WS-Policy]. W3C also published xml:id document that allows the same use [XMLID] that is a recommendation. Currently, the WS-Policy specification does not use the xml:id mechanism for uniquely identifying XML elements and relies on the WSS definition of id mechanism. 
Justification: 
The purpose of the xml:id specification is to have unique element identifiers to be recognized by all conformant XML processors. Currently, WS-Policy relies on WS-Security specification for generating URI references instead and requires the framework providers to recognize this alternate mechanism for processing references. As xml:id will be adopted, the support of xml:id in all XML processors may require WS-Policy to also allow utilization of xml:id. Further, the specification does not clarify whether the xml:id is permissable as an identification mechanism for a WS-Policy expression. 
Target: Section 4.2 of the WS-Policy, Appendix A. 
Proposal: 
Allow xml:id as a permissible mechanism for identifying policy expressions in addition to wsu:Id 
1. Replace 
{/wsp:Policy/@wsu:Id 
The identity of the policy expression as an ID within the enclosing XML document. If omitted, there is no implied value. To refer to this policy expression, a URI-reference MAY be formed using this value per Section 4.2 of WS-Security [WS-Security 2004].}


With 
/wsp:Policy/{@wsu:Id | @xml:id} 
The identity of the policy expression as an ID within the enclosing XML document. If omitted, there is no implied value. To refer to this policy expression, a URI-reference MAY be formed using this value per Section 4.2 of WS-Security [WS-Security 2004] when @wsu:Id is used. 
2. Repeat last example in Section 4.2 using xml:id in addition to wsu:id (last paragraph of Section 4.2) to illustrate the form. This is purely editorial. 
3. Add normative reference to xml:id [XMLID] in A.1.  
Personal Note: 
I have chosen to retain the reference on wsu:Id given the expected schedule of the publication rather than removing it due to existing support on this attribute in the existing implementations. 
We could also add a note in the framework/primer when it is not desirable to use xml:id but rely on wsu:id if the wg feels that is necessary. 
--umit 
[XMLID] http://www.w3.org/TR/xml-id/ 
[WS-Policy] http://dev.w3.org/cvsweb/~checkout~/2006/ws/policy/ws-policy-framework.html?content-type=text/html;%20charset=utf-8

---------------------- 
Dr. Umit Yalcinalp 
Architect 
NetWeaver Industry Standards 
SAP Labs, LLC 
Email: umit.yalcinalp@sap.com Tel: (650) 320-3095 
SDN: https://www.sdn.sap.com/irj/sdn/weblogs?blog=/pub/u/36238 
Received on Friday, 11 August 2006 23:54:55 GMT

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