Variablesare always based on a VariableType, i.e. they have a HasTypeDefinition Referencepointing to its VariableType.

Clientscan create Variablesusing the AddNodes Servicedefined in OPC 10000-4. The Servicerequires specifying the TypeDefinitionNodeof the Variable. A Variablecreated by the AddNodes Servicecontains all components defined by its VariableTypedependent on the ModellingRulesspecified for the components. However, the Servermay add additional components and Referencesto the Variableand its components that are not defined by the VariableType. This behaviour is Serverdependent. The VariableTypeonly specifies the minimum set of components that shall exist for each Variableof a VariableType.