Each NodeId that is used to describe the generated ObjectTypes shall use the Namespace “http://opcfoundation.org/UA/IOLink/IODD” and the identifierType String. The String of the NodeId of the ObjectType shall be composed of the VendorId, the DeviceId (in DeviceIdentity) and the version of the IODD (in DocumentInfo) using the format: “<VendorId>|<DeviceId>|<version>” like “888|67335|V1.1”. The InstanceDeclarations use this prefix followed by the BrowsePath. Variables and Methods, which might have several BrowsePaths use the BrowsePath coming from ParameterSet respectively MethodSet, Objects representing menus use the first BrowsePath that is defined in the IODD. The format is: “<ObjectTypeNodeId>||<BrowseName>[:<BrowseName>]”. The BrowseName only contains the String part, not the NamespaceIndex. An example is “888|67335|V1.1||ParameterSet:V_LifeTimeYears” as string-part of the NodeId of a Variable.
Defining the NodeIds of ObjectTypes based on IODDs is necessary so that OPC UA Clients accessing different OPC UA Servers implementing this specification and using the same IODDs can identify that they actually deal with the same types.