OPC Studio User's Guide and Reference
Points in Connectivity Model
Each connectivity must somehow identify the pieces of data it works with. We call them points. A connectivity can work with one or more types of points. The composite connectivity merges together the point types of multiple constituent connectivities.
For OPC Data Access (with the DAConnectivity component), following types of points exist:
For OPC Unified Architecture (with the UAConnectivity component), the following point type exists:
Note: Not all point types have the same capabilities. For example, the most common usage of Live Binding Model, Connectivity Explorer tool or the Excel Connector (RTD Server) is with subscriptions (to changing value). Because OPC-DA properties (as opposed to OPC-DA items) do not support subscriptions and we do not emulate them, the subscription operation on OPC-DA property points behaves as a single "get" of the property value.