The Data Access (DA) specification is primarily concerned with the real time acquisition and control of data within a process control environment.
DA servers are sources of data and could be a front end for a propriatory control systems or could be directly connected to physical I/O points. Any I/O point that is exposed by a DA server is called a DA item.
DA clients can directly read or write the DA items or they can establish subscriptions that require the DA server to send notifications only when the value of a DA item changes. |
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