AutomationML does not have modelling rules, like mandatory, optional or no modelling rule, that guide the creation of instances. Instantiating an SUC usually results in the creation of all InternalElements that are modelled as instance declarations on the type. However, since the UA modelling rules are present on the SUC of the OPC UA FX Libraries, engineering tools could do automatic postprocessing and delete the optional IEs from the type or let the user decide which optional IEs should be removed.

In OPC UA models, there are also attributes that only appear on data types and reference types that do not get propagated to instances, but in AML, the corresponding AML attribute types and AML interface classes, when instantiated propagate all the attributes associated with the type. In cases where the value of an attribute only has meaning on a type, the attribute shall contain an entry in the Additional Information collection of the Header “OPC:TypeOnly” to indicate that the attribute only has meaning on the type and can ideally be deleted or at least ignored on instances as shown in Figure A.20. Engineering tools should delete attributes marked “OPC:TypeOnly” when creating instances on export. Engineering tools shall ignore attributes marked “OPC:TypeOnly” on import in cases where the exporting tool fails to delete them when creating the instance.

Figure A.20 – “OPC:TypeOnly” additional Information in Header