To promote interoperability of clients and Servers, the OPC UA AddressSpace is structured as a hierarchy, with the top levels standardised for all Servers. Figure 1 illustrates the structure of the AddressSpace. All Objects in this figure are organised using Organizes References and have the ObjectType FolderType as type definition.

Figure 1 – Standard AddressSpace structure

The remainder of this provides descriptions of these standard Nodes and the organization of Nodes beneath them. Servers typically implement a subset of these standard Nodes, depending on their capabilities.