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

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Figure 1– Standard AddressSpace Structure

The remainder of this provides descriptions of these standard Nodesand the organization of Nodesbeneath them. Serverstypically implement a subset of these standard Nodes, depending on their capabilities.