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   Re: [xml-dev] Optional elements and restrictions

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Hi Marc,

The behaviour you describe is correct.  As you know, 
<DESTINATION_SYSTEM_ID/> is equivalent to
enumerations match "".

I personally don't see how an "empty element" can be considered equivalent 
to an "omitted element",  (e.g. consider <br /> in (early) (X)HTML), so 
changing the data source seems the correct thing.  If reality does not allow 
that, you could add an additional enumeration of the form:

<xs:enumeration value=""/>

But that would probably require additional application layer processing to 
fix it up!


Pete Cordell
for XML to C++ data binding visit

----- Original Message ----- 
From: "Lawson, Marc" <mlawson@relico.com>
To: <xml-dev@lists.xml.org>
Sent: Thursday, November 10, 2005 5:47 PM
Subject: [xml-dev] Optional elements and restrictions


In my schema, I have an "optional" element that looks like this:

<xs:element name="DESTINATION_SYSTEM_ID" minOccurs="0">
<xs:restriction base="xs:string">
<xs:enumeration value="TRUST_PROD"/>
<xs:enumeration value="TRUST_TEST"/>
<xs:enumeration value="PENSION_PROD"/>
<xs:enumeration value="PENSION_TEST"/>

My instance document will fail validation if the element is provided
without any data, as in...


However, the instance document will pass validation if the element is
omitted altogether.

I am hearing that it is best practice to allow both scenarios - the
"empty element" and the "omitted element" - in documents that are
provided.  Do I need to tell the company that is sending the file to
omit the element if it doesn't have data, or can I restructure the
schema to only validate elements that have data?

Any input is appreciated!
Marc Lawson


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