OPC UA is a platform-independent standard through which various kinds of systems and devices can communicate by sending request and responseMessages betweenClients andServers or NetworkMessages betweenPublishers andSubscribersover various types of networks. It supports robust, secure communication that assures the identity of OPC UA Applicationsand resists attacks.

In the Client Servermodel, OPC UA defines sets of Servicesthat Serversmay provide, and individual Serversspecify to Clientswhat Servicesets they support. Information is conveyed using OPC UA-defined and vendor-defined data types, and Serversdefine object models that Clientscan dynamically discover. Serverscan provide access to both current and historical data, as well as Alarmsand Eventsto notify Clientsof important changes. OPC UA can be mapped onto a variety of communication protocols and data can be encoded in various ways to trade off portability and efficiency.

In addition to the Client Servermodel, OPC UA defines a mechanism for Publishersto transfer the information to Subscribersusing the PubSubmodel.