IEC 62541-8-2020 pdf free download

IEC 62541-8-2020 pdf free download.OPC unified architecture — Part 8: Data access
Architecture unifiée OPC — Partie 8: Accés aux données.
A.4.1 Guidelines
The Data Access COM UA Proxy is a COM Server combined with a UA Client. It maps the Data Access address space of UA Data Access Server into the appropriate COM Data Access objects.
Sublauses A.4.1 through A.4.6 identify the design guidelines and constraints used to develop the Data Access COM UA Proxy provided by the OPC Foundation. In order to maintain a high degree of consistency and interoperability, it is strongly recommended that vendors, who choose to implement their own version of the Data Access COM UA Proxy, follow these same guidelines and constraints.
The Data Access COM Client simply needs to address how to connect to the UA Data Access Server. Connectivity approaches include the one where Data Access COM Clients connect to a UA Data Access Server with a CLSID just as if the target Server were a Data Access COM Server. However, the CLSID can be considered virtual since it is defined to connect to intermediary components that ultimately connect to the UA Data Access Server. Using this approach, the Data Access COM Client calls co-create instance with a virtual CLSID as described above. This connects to the Data Access COM UA Proxy components. The Data Access COM UA Proxy then establishes a secure channel and session with the UA Data Access Server. As a result, the Data Access COM Client gets a COM Data Access Server interface pointer.
A.4.2 Information Model and Address Space mapping
A.4.2.1 General
OPC UA defines 8 Node Class types in the address space Object, Variable, Method, ObjectType, VariableType, ReferenceType, DataType, View. The COM UA Proxy maps only the nodes of Node Class types Object, Variable to the OPC DA types as shown in the figure below. Only the nodes under the Objects node are considered for the COM UA Proxy address space and others such as Types and Views are not mapped. Figure A.4 shows an example mapping of OPC DA to OPC UA information.IEC 62541-8-2020 pdf free download.