Annex C (informative) Guidelines for the usage of OPC UA for Devices as base for Companion Specifications
In the previous sections it was shown how to use this specification when you want to use at least the TopologyElementType, providing you the capabilities to manage Parameters and Methods via ParameterSet and MethodSet and FunctionalGroups.
If the companion specification only wants to reuse other aspects of this specification, defined in the Interfaces in 4.5 or the AddIns “Locking” in 7 or Software update in 8, the companion specification does not need to derive from the ObjectTypes defined in this specification. Instead of, it can just implement the Interfaces or use the AddIns in their ObjectTypes and build an ObjectType-Hierarchy independent of this specification.
In Figure C.5, an example is given. The companion specification defines an ObjectType hierarchy, and uses the AddIns in the appropriate places (Lock and Transfer). The Interfaces can either be implemented by the ObjectTypes directly (Figure C.5), or by a sub-component in order to group the functionality (Figure C.7). In the second approach, the RootType does not implement the IVendorNameplate directly, but uses a component (Identification) implementing the Interface. Here, the FunctionalGroupType and the predefined name Identification is used. The B_Type extends the Identification and also implements the ITagNameplateType.
Figure C.6 – Example on how to use AddIns and Interface
The advantage of the first approach is, that the content of the Interface is directly at the ObjectType, whereas the advantage of the second approach is, that the content of the Interface is grouped in the sub-component. When the content of the Interface and the additional content of the ObjectType and its expected subtypes is rather small, the first approach is recommended. If the content of the Interface or the additional content of the ObjectType or its subtypes is rather large, the additional grouping Object is recommended, as it does not provide a flat list of sub-components, but groups them accordingly and thus makes it easier to use.
Figure C.7 – Example on how to use Interface with additional Object
IEC 61784: Industrial Communication Networks - Profiles
IEC 61499-1 ed2.0: Function Blocks –Part 1: Architecture
IEC 62591: Industrial communication networks - Wireless communication network and communication profiles - WirelessHART™
IEC 61131, IEC standard for Programmable Logic Controllers (PLCs)