The OPC UA Meta Model (the OPC UA Address Space Model) is represented by UML classes and UML objects marked with the stereotype <<TypeExtension>>. Those stereotyped UML objects represent DataTypesor ReferenceTypes. The domain model can contain user-defined ReferenceTypes andDataTypes, also marked as <<TypeExtension>>. In addition, the domain model contains ObjectTypes, VariableTypes etc. represented as UML objects (see Figure B.1).