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An InstanceDeclaration marked with the ModellingRule Mandatory fulfils exactly the semantic defined for the NamingRule Mandatory. That 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 19 illustrates the example.

Figure 19 – Use of the Standard ModellingRule Mandatory

In 6.4.4.5.3 a complex example combining the Mandatory and Optional ModellingRules is given.