Re: Sometimes an empty value means "use the default value" and sometimes it doesn't ... right?

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Re: Sometimes an empty value means "use the default value" and sometimes it doesn't ... right?

Costello, Roger L.
Ken, Hello,

Sorry, I was not clear in my message.

I was not asking a question about semantics or meaning.

I was asking a question about the behavior of XML Schema validators.

Hopefully this question will be clearer:

    The XML Schema validator determines the
    value of the empty Altitude element
     to be the default, 100.

    The XML Schema validator determines the
    value of the empty Title element
     to not be the default; instead the value
    is the empty string.

Right?

/Roger


At 2012-08-23 19:04 +0000, Costello, Roger L. wrote:
>Thus sometimes an empty value means "use the default value" and
>sometimes it doesn't.  Right?

What something "means" is up to the semantics of the applications
that act on the content, and to the vocabulary designers who are
trying to impose common understandings of use amongst those employing
the vocabulary.

To add to your list, in UBL an empty value means "error" ... there is
an instance rule that no element shall be empty because it could be
ambiguous between trading partners.

   http://docs.oasis-open.org/ubl/os-UBL-2.0/UBL-2.0.html#d0e3645
   "Use of empty elements within XML instance documents is a
    source of controversy for a variety of reasons."

I hope this helps.

. . . . . . . . . Ken


--
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Re: Sometimes an empty value means "use the default value" and sometimes it doesn't ... right?

G. Ken Holman
At 2012-08-23 19:32 +0000, Costello, Roger L. wrote:

>Sorry, I was not clear in my message.
>
>I was not asking a question about semantics or meaning.
>
>I was asking a question about the behavior of XML Schema validators.
>
>Hopefully this question will be clearer:
>
>     The XML Schema validator determines the
>     value of the empty Altitude element
>      to be the default, 100.
>
>     The XML Schema validator determines the
>     value of the empty Title element
>      to not be the default; instead the value
>     is the empty string.
>
>Right?

I apologize for not recognizing your question.  The specification
talks to your point directly:

http://www.w3.org/TR/2004/REC-xmlschema-1-20041028/#Element_Declaration_details
   Note: The provision of defaults for elements goes beyond what
   is possible in XML 1.0 DTDs, and does not exactly correspond
   to defaults for attributes. In particular, an element with a
   non-empty {value constraint} whose simple type definition
   includes the empty string in its lexical space will
   nonetheless never receive that value, because the {value
   constraint} will override it.

I hope this helps.

. . . . . . . .  Ken


--
Public XSLT, XSL-FO, UBL and code list classes in Europe -- Oct 2012
Contact us for world-wide XML consulting and instructor-led training
Free 5-hour lecture: http://www.CraneSoftwrights.com/links/udemy.htm
Crane Softwrights Ltd.            http://www.CraneSoftwrights.com/x/
G. Ken Holman                   mailto:[hidden email]
Google+ profile: https://plus.google.com/116832879756988317389/about
Legal business disclaimers:    http://www.CraneSoftwrights.com/legal