One modelling construct to add information to References, is to provide an intermediate Objectas proxy with additional information (see Figure A.1). The approach often makes sense. For example, to provide information about the physical cable connecting two devices represented as Nodes, another Nodeis added representing the cable, and both device Nodesare connected to the cable Node. The disadvantage of the approach is, that a Clientcannot natively follow the Referenceto the target directly, but always gets to the intermediate Objectfirst and from there to the original target. Therefore, the ReferenceDescriptionuses an approach, where the Referencedirectly connects both Nodeswithout the need to deal with an intermediate Object.


Figure A.1– Refinement of References by Proxy Object


[1] OPC 30010, OPC UA for AutoId Devices

[2] OPC 30120, OPC UA for IO-Link Devices and IO-Link Masters

[3] OPC 10000-100, OPC Unified Architecture – Part 100: Devices