There are two different use cases when creating an instance ‘A’ based on a TypeDefinitionNode ‘A_Type’. Either ‘A’ is used as normal instance or it is used as InstanceDeclaration of another TypeDefinitionNode.
In the first case, it is not required that newly created or referenced instances based on InstanceDeclarations have a ModellingRule, however, it is allowed that they have any ModellingRule independent of the ModellingRule of their InstanceDeclaration.
In Figure 17 an example is given. The instances A1, A2, and A3 are all valid instances of Type_A, although B of A1 has no ModellingRule and B of A3 has a different ModellingRule than B of Type_A.
Figure 17 – Example on changing instances based on InstanceDeclarations
In the second case, all instances that are referenced directly or indirectly from ‘A’ based on InstanceDeclarations of ‘A_Type’ initially maintain the same ModellingRule as their InstanceDeclarations. The ModellingRules may be updated; the allowed changes to the ModellingRules of these Nodes are the same as those defined for subtyping in 188.8.131.52.
In Figure 18 an example of such a scenario is given. Type_B uses an InstanceDeclaration based on Type_A (upper part of the Figure). Later on the ModellingRule of the InstanceDeclaration A1 is changed (lower part of the Figure). A1 has become the NamingRule of Mandatory (changed from Optional).
Figure 18 – Example on changing InstanceDeclarations based on an InstanceDeclaration