The manufacturer or system integrator of a Compressed Air Systemmay wish to add Variables, Objects, or Methodswhich are not yet defined by this specification. In such a case the additional Variables, Objects, or Methodsshall be added to an appropriate FunctionalGroupof the Component. It is important, that the Variables, Objects, or Methodswhich are added match the description of the FunctionalGroupthey are added to. If there is no FunctionalGroupavailable the Variables, Objects, and Methodsfit in, the manufacturer or system integrator shall create a new Objectof the FunctionalGroupType.

It is also possible to define a subtype of the FunctionalGroupType or one of its subtypes to define a new collection of Variables, Objects, or Methods. When subtyping, the manufacturer or system integrator should keep in mind, that all Variables, Objects, and Methodsof the supertype are also available to the new subtype.

In general, no new Variables, Objects, or Methodsshall be created that are already available in this specification. If the manufacturer or system integrator wants to add already existing Variables, Objects, or Methodsto another FunctionalGroup, the Organizes ReferenceType shall be used.

When creating Variableswhich are representing Quantities, the BaseAnalogType or one of its subtypes shall be used as TypeDefinition. When creating Variablewhich are not representing Quantities, the DataItemType or one of its subtypes, other than the BaseAnalogType, shall be used as TypeDefinition. Either way, the Definition Propertyshall be instantiated to further clarify the intended purpose of the Variable.

Figure 12illustrates some usage examples on how to extend FunctionalGroupsof a compressor.

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Figure 12– Extending FunctionalGroups