This specification is organized as a multi-part specification, as illustrated in Figure 1.

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Figure 1– OPC UA Specification Organization

Parts 1 through 7 and Part 14 specify the core capabilities of OPC UA. These core capabilities define the structure of the OPC AddressSpaceand the Servicesthat operate on it. Part 14defines an OPC UA publish subscribe pattern in addition to the Client Serverpattern defined by the Servicesin Part 4. Parts 8 through 11 apply these core capabilities to specific types of access previously addressed by separate OPC COM specifications, such as Data Access (DA), Alarms and Events (A&E) and Historical Data Access (HDA). Part 12describes Discoverymechanisms for OPC UA and Part 13describes ways of aggregating data.

Readers are encouraged to read Parts 1 through 5 of the core specifications before reading Parts 8 through 14. For example, a reader interested in UA Data Access should read Parts 1 through 5 and 8. References in Part 8may direct the reader to other parts of this specification.