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There are 2 messages on the comments list requesting more powerful xs:all [1][2]. There is another comment on xs:all [3] complaining about our limitations on xs:all. Basically the 2 messages are asking for 3 enhancements: 1. Allow maxOccurs>1 on elements inside <xs:all> 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. 2. Allow <xs:all> to appear inside <xs:sequence> and <xs:choice> 3. Allow xs:all extensions, to add new elements into all model groups. [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://lists.w3.org/Archives/Public/www-xml-schema-comments/2005JanMar/0010.html
The WG reached partial agreement on this in March 2006, adopting a proposal to allow maxOccurs > 1 and allow wildcards in all-groups. Other aspects of the proposal were not decided. A wording proposal reflecting the partial consensus reached in March was submitted to the WG in July 2006 and approved on July 21; it is reflected in the (member-only) status quo drafts. The remainder of this bug remains in status 'needsAgreement'.
Part of this comment has been accepted by the WG, and implemented. The rest has been postponed on the grounds that it is too much work for now.
This note, sent to the original commentators, captures the workgroup's intentions for resolving this issue. 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 --------------------------------------