Data Access is an information model for real-time data, i.e. data that represent current state and behaviour of the underlying industrial or business process. Access is provided with Read, Write and Subscription Services. Typical sources are sensors, control devices, position transducers and more.
Such information is typically used by Clients for user displays, or to monitor and control the process.
- device data such as sensor measurement or actuator state
- energy consumption, energy price
- calculated data
- business data
- dynamically-changing system data (such as stock quotes)
- diagnosis data
In automation systems the data is often located on I/O cards or on other devices such as controllers and input/output modules, connected by serial links via field buses or other communication links. The DA model therefore also defines codes that specify the quality of the physical connection.
Note – Data Access is specified in OPC UA Part 8