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Subject: [ubl] version attribute - Re: [ubl] Minutes of Atlantic UBL TCcall2 November 2005

"Plus folk are rightly expecting minimal departure from the
promises of the original NDR and confidence in UBL could 
perhaps be damaged if too much of the NDR1 is preserved
in 2.0 (minor versioning would appear, by nature, to apply
beyond UBL 1.0)."

sorry I meant

"damaged if too much of the NDR1 is NOT preserved
in 2.0"

Plus I'd add that not only would a UBL-specific version
attribute be proprietary as far as software is concerned
but that such an attribute would be specific to a 
particular version of UBL too (since it doesn't exist in
UBL 1.0) so applications upgrading to UBL 1.0 have to
be changed a lot to deal with 2.x and application designed
for 2.0 might not work with 1.0 (not just semantically but

>>> "Stephen Green" <stephen_green@bristol-city.gov.uk> 04/11/05 16:18:32 >>>
Objection regarding version attribute

I'd refer to Eduardo and Arofan's excellent XML 2003 paper
section 4 - first paragraph
"The scope of UBL, and the potential for having several versions of the same schema extant at the same time, places
emphasis on some particular aspects of versioning. First, the manageability of a versioned "package" becomes
very important, because there is little or no control over the applications that use it. Users must be able to easily
distinguish one version from another, and applications should be able to do the same, preferably without having
to implement any functionality that is specific to one particular version. (It should be pointed out that, while XSD
does offer us a "version" attribute on the schema element, there is no standard on how that field is to be used. Any
versioning approach that relies on it, or similar other "version" attributes applied to various elements, is in essence

I agree that a UBL specific version attribute has a downside
of being 'proprietary', too specific to UBL. It does allow the
attribute to appear in an instance which improves on the
xsd:version attribute, but is more proprietary and has to be
catered for in software in a way that is specific to UBL. This
may exacerbate the impact on other standards (like ebXML)
and subsets (see my previous email today), not to mention 
customizations (which have to have a way to show they 
are a customisation of a particular minor version).

Add to this the problem of derivation which needs a
namespace different from the one importing it and I
think there is a very strong argument for keeping the
minor version number in the namespace in the case of
UBL - and I see less of a reason for consigning it to a
UBL-defined attribute. Then there is the problem that 
references to the value of the attribute have lack of 
precision of 'vocabulary' control (e.g. is '2.0' the same 
as '2:0' when version needs to be quoted outside of

Plus folk are rightly expecting minimal departure from the
promises of the original NDR and confidence in UBL could 
perhaps be damaged if too much of the NDR1 is preserved
in 2.0 (minor versioning would appear, by nature, to apply
beyond UBL 1.0).

Even if we were to abandon substitution groups and
derivation and deltas (unless these can be kept somehow
without substitution groups in the mechanism), I'd still hope
that we kept the minor version in the namespace (not least 
because it allows necessary precision if just the namespace
and not the version can be referenced in trading partner
agreements and business process specifications and likewise
in customisations).

All the best


>>> <jon.bosak@sun.com> 04/11/05 00:44:07 >>>


   It was decided at the close of this meeting that due to
   attendance at XML 2005, we will not be holding the Atlantic
   call 16 November.  We *will* be holding this call at its
   regularly scheduled time next week (9 November).


   Jon Bosak (chair)
   Mikkel Brun
   Mavis Cournane
   Michael Grimley
   Betty Harvey
   Bryan Rasmussen
   Kumar Sivaraman
   Paul Thorpe


   Additions to the calendar:


   Review of Pacific and Europe/Asia calls

      No comments.

   Schedule review
      Including attendance at April meeting in Brussels

      JB: This meeting is to be hosted by CEN/ISSS in Brussels the
      week of 24 April.  It accidentally got dropped from the 2.0
      schedule.  We very much want to accept the offer to host,
      but neither JB nor TM will be available to chair.  We need
      to know who can commit to be there.

      ACTION: JB to poll the TC for attendance at the April F2F in


   ACTION: JB to create the first draft of index.htm.

      Status: Done.

   ACTION: TC members visiting NYC in October or November to check
   out the Sun facilities and see whether they are suitable for a
   UBL TC meeting.  JB will be coming through in mid-November and
   will also check then.

      Status: Pending.

   ACTION: JB to post a question on ubl-dev: What do other widely
   used schemas do about minor version namespace URIs?

      Status: Done.

   ACTION: Everyone involved in the development of the support
   pieces to give JB time estimates.

      JB: We have estimates for SBS from SG.  We still need
      estimates for code lists, HISC, and the business process

      ACTION: MB to check with PB regarding time estimates for the
      business process scenarios.


NDR work session: Minor versioning.  See


   *** NOTE that as usual, voting members have a week to register
   any disagreement with the decisions described below.  If no
   disagreement is registered, the decisions arrived at during the
   call will become officially adopted by the TC. ***

Question 1: Should minor-version schemas only contain the deltas,
or should everything be redeclared (with the 'ccts:Version'
documentation component reflecting the version of individual

   Discussion: Deltas make clear exactly what's been changed or
   added and make it easy to determine backward compatibility.

   AGREED that minor-version schemas should only contain the

Question 1.a: Should we have minor-version spreadsheets that only
capture the deltas and their relationship to the major version?

   Discussion: Providing full spreadsheets for the minor version
   allows someone coming in at that stage to see the whole
   picture.  It also sidesteps the problem of how to capture the
   relationship between major and minor at the spreadsheet level
   (we can just add a flag to mark the items that have been added
   in the minor version).

   AGREED that the minor version spreadsheets should contain the
   entire vocabulary, with a flag to indicate what has been
   changed or added in the minor version.

   AGREED that we thank Bill Burcham for his contribution of a
   method that could have been employed if we had decided that the
   minor version spreadsheets would contain only the deltas.

   Discussion: It may be difficult for tools to generate the
   deltas (see decision on Question 1 above) from the full
   spreadsheets.  It's possible that the tool we use will only be
   able to create major version schemas, and that we will have to
   create the minor version schemas by hand.

   AGREED that while we hope that tools can be configured to
   create the minor version delta schemas from the full
   spreadsheets, we are willing to adopt this policy even if it
   means that the minor version schemas have to be created by

Question 2: Should the namespace name change for minor versions?
How about the namespace prefix?

   Discussion: Our assumption is that a minor version of UBL may
   add new content but will not change the meaning of anything
   declared in the major version schemas.  It therefore appears
   that the best approach is to separate semantic identity from
   versioning.  But doing so will require us to specify expected
   behavior of UBL processors when presented with instances
   exhibiting different versioning information.

   AGREED that minor versions should use the same namespace as the
   major version from which they are derived (which means, for
   example, that the namespace for UBL 2.0 should reference "UBL
   2" rather than "2.0") and that the version should be specified
   in a separate attribute TBD.

   AGREED that the namespace prefix stays the same in minor

   ACTION: NDR editors to propose a suitable version attribute to
   be used by all UBL instances in time for discussion during the
   Atlantic TC call 9 November.

   ACTION: At the Manhattan F2F in January, NDR editors to develop
   a specification of expected behavior of UBL processors when
   encountering a version different from the one for which they
   were designed.  (For example, UBL processors expecting a
   version 2.x when presented with an instance conforming to a
   later version 2.y might be required to attempt validation
   against the 2.x schemas and reject the instance if errors are

   Discussion: We note that some users may not understand that the
   specification of namespace prefixes in our NDRs does not
   hardwire those prefixes in conformant instances.

   ACTION: At the Manhattan F2F in January, NDR editors to develop
   a best practice note for namespace prefixes.  (For example,
   "For ease of comprehension it is recommended that the prefixes
   specified in our NDRs are used in instances, but applications
   must be able to process arbitrary prefix declarations per the
   XML Recommendation.")

Question 3: What, specifically, determines whether a new version
of the schema is actually a 'minor' or 'major' release? (If the
schema only includes the deltas, and utilizes xsd:derivation
concepts, the answer should be simpler than if the versioning is
strictly model-based.)

   Discussion: We have already adopted the definitions given by
   Eduardo Gutentag in his message of 18 October 2005, but we note
   that his definition of backward compatibility transposes X and

      c) backwards compatibility -- a schema X is said to be
      backwards compatible with a schema Y if documents that
      validate against schema X also validate against schema Y,
      and schema X follows (in time, or in version) schema Y.

      In other words, if all documents that validate against
      MySchema v1.0 also validate against MySchema v1.1, then
      MySchema v1.1 is said to be backwards compatible; but there
      is no expectation that any document that validates against
      MySchema v1.1 must also by necessity validate against
      MySchema v1.0

   The example shows that the definition should read "and schema Y
   follows (in time, or in version) schema X."

Question 4: Is (are?) Substitution Groups still on the table?

   AGREED: We will not use substitution groups for minor

Question 5: What should be the normative version of UBL? Schema,
Model or both.

   Discussion: XML inherits from SGML the doctrine that documents
   are normatively specified by the combination of formal
   declarations plus comments.  Properly annotated schema
   formalisms such as DTD (W3C), XSD (W3C), RELAX NG (ISO),
   Schematron (ISO), and ASN.1 (ITU) are the standard mechanisms
   for establishing the validity of XML instances; no such
   standard exists for mechanically checking an instance against a
   model.  And since there is no way of proving that a model and a
   schema describe exactly the same thing, we cannot say that both
   are normative.

   AGREED that UBL is normatively specified by the schemas plus
   associated normative prose.

Jon Bosak

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