An InstanceDeclaration marked with the ModellingRule Mandatory means that for each existing BrowsePath on the instance a similar Node shall exist, but it is not defined whether a new Node is created or an existing Node is referenced.
For example, the TypeDefinitionNode of a functional block “AI_BLK_TYPE” will have a setpoint “SP1”. An instance of this type “AI_BLK_1” will have a newly-created setpoint “SP1” as a similar Node to the InstanceDeclaration SP1. Figure 26 illustrates the example.
Figure 26 – Use of the Standard ModellingRule Mandatory
In 22.214.171.124.2 a complex example combining the Mandatory and Optional ModellingRules is given.