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Re: [xml-dev] Preoccupation with zero, empty strings, empty elements, empty everything

At 2013-12-07 14:38 -0500, John Cowan wrote:
On Sat, Dec 7, 2013 at 1:10 PM, <<mailto:gkholman@cranesoftwrights.com>gkholman@cranesoftwrights.com> wrote:

"UBL takes the position that empty elements do not provide the level
of assurance necessary for business information exchanges and
therefore must not be used."

... and have reduced the requirement to the following rules:

[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.

The full rationale doesn't seem to exclude the use of inherently empty elements (those with a content model of EMPTY) that have attributes, yet the rule does.
Except that none of our elements are inherently empty and so the situation is not encountered. Every data item (simple content element) is based on one of a selection of data type representations, none of which provides for an empty value.

   [IND6] The absence of a construct or data in a UBL instance
          document MUST NOT carry meaning.

In that case, how does one express the notions "data unavailable"
and "data does not exist" in UBL?
If an invoice, say, doesn't have a Note, then it just doesn't have a <cbc:Note> element. But that is merely a property of the invoice that it doesn't have a note ... there are no business decisions leveraged on the absence of a note. We encouraged the business analysts on the team to design the document objects to be declarative such that everything is manifest with no interpretation needed of absent content as that would presume the recipient and the sender agreed upon what the absence meant. Whereas when an element exists, its definition is part of the UBL standard.

I'll talk with my committee colleagues to get some specific examples.

. . . . . . . . Ken

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