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About OPC Unified Architecture

The OPC Unified Architecture (OPC UA) standard combines all the capabilities of OPC Data Access and OPC Historical Data Access standards (together, referred to as "OPC Classic") and adds various additional capabilities into a single, extensible standard. OPC UA servers provide a single namespace which organizes the data available on the server, into a hierarchical view of nodes (also called items in OPC Classic terminology). Nodes on OPC UA servers can be object nodes, which organize other nodes, or variable nodes, which have a value representing some process value on the server. Variable nodes can contain other variable nodes. Nodes are arranged in a number of representations; for OPC Toolbox™, the nodes are exposed as a hierarchical tree, with nodes containing subnodes called children.

OPC UA servers are required to publish a node in their namespace named "Server". The Server node provides information about the OPC UA server, including the capabilities of the server, specific limitations of the server, and other information related to the server. OPC Toolbox provides selected information from the Server node as properties of the client you create to connect to that server. For information on client properties, see opc.ua.Client.

OPC UA servers may or may not historize Variable nodes. For historizing nodes, OPC UA servers store prior values of the node, and can provide that history to OPC UA Clients as raw data (data points at the times that the server stored the Value), or as data at requested times (the server interpolates the raw data using either sample-and-hold or linear interpolation), or as processed data, using a predefined aggregate function that is requested by the user. Each OPC UA server describes which Aggregate Functions are supported by that server. "OPC UA Aggregate Functions" describes the standard aggregate functions defined in the OPC UA Specification. Servers may implement custom aggregate functions; consult the OPC UA Server reference for information on how those functions work. OPC Toolbox provides a client interface to the OPC UA servers which allows you to browse the server namespace to find nodes of interest. OPC Toolbox supports the opc.tcp binary protocol and anonymous, unsecured connections. For some of the tasks you can perform with OPC Toolbox, see the related examples at the end of this topic.

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