The editor reports a validation error if there are zero OutputField's.

However following the discussion on FAI-380 we should support an optional Output element in the XML output.

This would mean (off the top of my head, but may need a little more thought):-

• Remove the check for zero OutputField's.
• If there are zero OutputField's then set the Output element to undefined to prevent an empty <Output /> element in the XML.
• Consequentially if we're to rely on an undefined Output property we should check the unmarshalling XML -> model and adding the first OutputField...

For reference:

<xs:element ref="Output" minOccurs="0"/> meaning that we don't technically need an Output element.

<xs:element ref="OutputField" minOccurs="1" maxOccurs="unbounded"/> where from the current validation came.