OPC UA allows an Interface to be applied to type objects or to instances. The OPC UA FX Information Model can be included via Interfaces into an instance of an existing Information Model. This type of update is illustrated in Figure B.4Figure 4.

Figure B.4 – Extending an instance with Interfaces

This set of extensions is very similar to what is described in Annex B.3.2.1, but the Interfaces are applied to the instance instead of the type. The instance will include each of the Interfaces. Furthermore, the references are added to provide the mapping to the existing Variables.

When to use:

• Extending instances with Interfaces is used when an Information Model is already instantiated, and the type definition cannot be extended. Usually, this is instance-specific, and it is difficult to be reused. It can be used in a device or application that wants to utilize an existing Information Model with OPC UA FX but does not plan on creating many instances of this Object. An example could be a device that ships with a single instance of this Object. It does not require any update to a companion or vendor specification.