Optional elements and restrictions

Hi,

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

<xs:element name="DESTINATION_SYSTEM_ID" minOccurs=”0”>

<xs:simpleType>

<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"/>

</xs:restriction>

</xs:simpleType>

</xs:element>

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

<DESTINATION_SYSTEM_ID/>

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