Re: [Bug 2506] XML Schema Support for <all> groups

Thank you very much.  I'm sure I speak for others in the workgroup in 
thanking you for your prompt response and for your support of this 
resolution.

--------------------------------------
Noah Mendelsohn 
IBM Corporation
One Rogers Street
Cambridge, MA 02142
1-617-693-4036
--------------------------------------








Steve Hanson <smh@uk.ibm.com>
Sent by: www-xml-schema-comments-request@w3.org
03/21/2007 10:52 AM
 
        To:     www-xml-schema-comments@w3.org
        cc:     noah_mendelsohn@us.ibm.com
        Subject:        Re: [Bug 2506] XML Schema Support for <all> groups



The XML Schema 1.1 enhancements to xsd:all are a useful extension to the 
capability of XML Schema, and are sufficient to address my comments for 
now. 

Regards, Steve

Steve Hanson
WebSphere Message Brokers
Hursley, UK
Internet: smh@uk.ibm.com
Phone (+44)/(0) 1962-815848 


noah_mendelsohn@us.ibm.com 
20/03/2007 20:44 


To
Steve Hanson/UK/IBM@IBMGB, Robert Nielsen <robertnielsen@nc.rr.com> 
cc
www-xml-schema-comments@w3.org 
Subject
[Bug 2506] XML Schema Support for <all> groups








Gentlemen,

In 2005, both of you sent comments  [1,2]  requesting ehancements to the 
support of <all> groups in the W3C XML Schema Language.  To track work on 
the concerns you raised, the workgroup opened an "issue", which is number 
2506 in our Bugzilla tracking system [3].  The purpose of this note is to 
inform you of our intentions for changes to support for <all> groups in 
XML Schema version 1.1, and to alert you to our intended disposition of 
this issue.

As summarized in the Bugzilla formulation, several functional improvements 

were requested.   Here is what is proposed for those in XML Schema 1.1:

> 1. Allow maxOccurs>1 on elements inside <xs:all>

This will be provided.  maxOccurs>1 will be allowed on <xs:all> groups.

> 1.1 And require that same named elements in the instance have to be 
> together (no interleaving). That is, A,A,B,B,B, instead of A,B,B,A.

This was discussed extensively, and the workgroup could not reach 
consensus that the additional complexity in the specifications, in 
implementations, in testing, and so on was justified by the added utility 
of providing both options.  Accordingly, the validation rules when 
maxOccurs>1 are what is described above as "interleaving".  If we have 
a(maxOccurs=2) and b(maxOccurs=3) then both of the above are valid.

> 2. Allow <xs:all> to appear inside <xs:sequence> and <xs:choice>

This was deemed sufficiently complicated to implement that the function is 

not being provided in XML Schema 1.1

> 3. Allow xs:all extensions, to add new elements into all model groups.

This is supported in XML Schema 1.1.  When extension of an <all> group is 
used an an XML Schema document, then only the "new" elements must be 
explicitly identified on the specification of the derived type.  Others 
are inherited from the base. 

Although not explicitly requested in your notes, and not tracked under the 

same bugzilla bug number, Schema 1.1 also includes significant 
enhancements to the treatment of complex type restriction.  In general, in 

Schema 1.1, a content model is a legal refinement of its base if every 
sequence of elements accepted by the derived model is also valid per the 
base (that's a bit of a simplification, but sufficient I think for 
purposes of this note.)  A consequence of this is that restrictions of 
<all> groups are now supported.  Indeed,  it's possible for <all> groups 
to restrict other groups such as sequences and vice versa. (e.g. the 
sequence {a,b} is a valid restriction of the all group all(a,b).

The workgroup leaves open the possibility that some of the functions that 
you requested that are not supported in Schema 1.1 might be supported in 
some future release.

We would be very grateful if you would send a note to the XML Schema 
Comments mailing list (www-xml-schema-comments@w3.org) confirming that 
these dispositions of your comments are acceptable to you, or if not, 
explaining any remaining concerns.  Thank you very much.

Noah Mendelsohn
for the W3C XML Schema Workgroup

[1] 
http://lists.w3.org/Archives/Public/www-xml-schema-comments/2005JanMar/0038.html


[2] 
http://lists.w3.org/Archives/Public/www-xml-schema-comments/2005JanMar/0043.html


[3] http://www.w3.org/Bugs/Public/show_bug.cgi?id=2506

--------------------------------------
Noah Mendelsohn 
IBM Corporation
One Rogers Street
Cambridge, MA 02142
1-617-693-4036
--------------------------------------










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Received on Thursday, 22 March 2007 19:55:38 UTC