An InstanceDeclarationmarked with the ModellingRule Mandatorymeans that for each existing BrowsePathon the instance a similar Nodeshall exist, but it is not defined whether a new Nodeis created or an existing Nodeis referenced.

For example, the TypeDefinitionNodeof 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 InstanceDeclarationSP1. Figure 26illustrates the example.

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Figure 26– Use of the Standard ModellingRule Mandatory

In 6.4.4.4.2a complex example combining the Mandatoryand Optional ModellingRulesis given.