An incorrect element citation in the NDR

["G. Ken Holman" <gkholman@CraneSoftwrights.com>]

I found something else regarding the NDR during the UBL class that I 
taught last week.

At 2008-05-06 16:47 -0700, jon.bosak@sun.com wrote:
>AGENDA FOR ATLANTIC UBL TC MEETING
>15:00 - 17:00 UTC WEDNESDAY 7 MAY 2008
>http://www.timeanddate.com/worldclock/fixedtime.html?month=5&day=7&year=2008&hour=15&min=0&sec=0
>...
>UBL 2.0 NDR EDITORIAL REVIEW (TRACKING)
>
>    We need to add a section on code list metadata; see
>
>       http://lists.oasis-open.org/archives/ubl/200803/msg00001.html

I'm pretty sure this mistake has been around for many editions, but 
I've confirmed it is also in the edition distributed with this posting:

   http://lists.oasis-open.org/archives/ubl/200803/msg00007.html

Rule ELD7 in section 5.4 Empty elements reads:

   "[ELD7] Empty elements MUST not be declared, except in the
   case of extension, where the 'UBL Extensions' element is used."

This sentence is referencing the incorrect element.  I believe it 
should read as:

   "[ELD7] Empty elements MUST not be declared, except in the
   case of extension, where the 'UBL ExtensionContent' element is used."

This is because the <ext:ExtensionContent> declaration allows that 
element to be empty, while both the <ext:UBLExtension> and 
<ext:UBLExtensions> element declarations do not allow either one to be empty.

An NDR rule cannot allow something that is not allowed by the schema 
expressions, so I'm supposing that the review of this rule didn't 
catch that the incorrect element was being referenced.  Probably my oversight.

I note that the correct element is cited in the additional document 
constraint [IND5] in section 6.3 of 
http://docs.oasis-open.org/ubl/os-UBL-2.0/UBL-2.0.html#d0e3645 where it reads:

    "[IND5] UBL conformant instance documents MUST NOT contain an element
    devoid of content or containing null values, except in the case of
    extension, where the UBL ExtensionContent element is used."

To recap, the <ext:ExtensionContent> element is allowed to be empty 
because a receiving or intermediate process may need to elide all 
content in unrecognized namespaces, thus resulting in this element 
being empty.  Note that the sibling meta data for the extension is 
not elided because it is in a UBL namespace, thus allowing the 
application to detect the presence and (if included) identity of an 
extension without having to have the actual extension present in the instance.

I hope this helps.

. . . . . . . . . . . Ken

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