The OPC UA Specifications are organised as a multi-part document. The following list of references provide link to each of the parts. Also referenced are applicable API documents. This companion specification assumes that all OPC UA Application support as a minimum version 1.02 of the OPC UA specifications.
Part 1: OPC UA Specification: Part 1 – Concepts
http://www.opcfoundation.org/UA/Part1/
Part 2: OPC UA Specification: Part 2 – Security Model
http://www.opcfoundation.org/UA/Part2/
Part 3: OPC UA Specification: Part 3 – Address Space Model
http://www.opcfoundation.org/UA/Part3/
Part 4: OPC UA Specification: Part 4 – Services
http://www.opcfoundation.org/UA/Part4/
Part 5: OPC UA Specification: Part 5 – Information Model
http://www.opcfoundation.org/UA/Part5/
Part 6: OPC UA Specification: Part 6 – Mappings
http://www.opcfoundation.org/UA/Part6/
Part 7: OPC UA Specification: Part 7 – Profiles
http://www.opcfoundation.org/UA/Part7/
Part 8: OPC UA Specification: Part 8 – Data Access
http://www.opcfoundation.org/UA/Part8/
Part 9: OPC UA Specification: Part 9 – Alarms and Conditions
http://www.opcfoundation.org/UA/Part9/
Part 10: OPC UA Specification: Part 10 – Programs
http://www.opcfoundation.org/UA/Part10/
Part 11: OPC UA Specification: Part 11 – Historical Access
http://www.opcfoundation.org/UA/Part11/
Part 12: OPC UA Specification: Part 12 – Discovery
http://www.opcfoundation.org/UA/Part12/
Part 13: OPC UA Specification: Part 13 - Aggregates
http://www.opcfoundation.org/UA/Part13/
API Standard 17F - Standard for Subsea Production Control Systems:
http://www.api.org/products-and-services/standards/purchase
The OPC UA Specifications are also available from the IEC as IEC 62541