gml:operationVersion is the version of the coordinate transformation (i.e., instantiation due to the stochastic nature of the parameters). Mandatory when describing a transformation, and should not be supplied for a conversion.
<element name="operationVersion" type="string"><annotation><documentation>gml:operationVersion is the version of the coordinate transformation (i.e., instantiation due to the stochastic nature of the parameters). Mandatory when describing a transformation, and should not be supplied for a conversion.</documentation></annotation></element>