This element serves as the head of a substitution group
for extensibility elements that wish to appear as children of
wsdl:interface/wsdl:operation/wsdl:input\output
Abstract Element interfaceOpMsgExt
The interfaceOpMsgExt element cannot have "xsi:nil" as an attribute.
The interfaceOpMsgExt element in XML instance can be substituted with other elements.
<xs:documentation>
This element serves as the head of a substitution group
for extensibility elements that wish to appear as children of
wsdl:interface/wsdl:operation/wsdl:input\output
</xs:documentation>