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The primary objective of the OPC UA AddressSpace is to provide a standard way for Servers to represent Objects to Clients. The OPC UA Object Model has been designed to meet this objective. It defines Objects in terms of Variables and Methods. It also allows relationships to other Objects to be expressed. Figure 2 illustrates the model.

Figure 2 – OPC UA Object Model

The elements of this model are represented in the AddressSpace as Nodes. Each Node is assigned to a NodeClass and each NodeClass represents a different element of the Object Model. Clause 5 defines the NodeClasses used to represent this model.