An InstanceDeclaration is an Object, Variable or Method that references a ModellingRule with a HasModellingRule Reference and is the TargetNode of a hierarchical Reference from a TypeDefinitionNode or another InstanceDeclaration. There shall be no two TypeDefinitionNodes referencing the same InstanceDeclaration with a hierarchical Reference, either directly or from another InstanceDeclaration of that TypeDefinitionNode, i.e. an InstanceDeclaration belongs to exactly one TypeDefinitionNode.

The type of an InstanceDeclaration may be abstract, however the instance must be of a concrete type.