Types involved in the live mapping for OPC Data need to be annotated with the DAType attribute (OPC Classic) or the UAType attribute (OPC-UA). If you derive your types from one of the Mapped Node Classes (such as DAMappedNode or UAMappedNode), this attribute is inherited and you do not have to explicitly specify it again.

Both reference and value types are allowed in the live mapping.

In addition to the DAType (or UAType) attribute, you can use other (“propagated parameter”) attributes on your type, as seen from the table in the Attributes for Live Mapping chapter. These additional attributes do not have direct effect on the type itself, but influence all members of that type. For example, if you specify the DASubscription attribute on your type, and specify the requested update rate, this update rate will be used with all members of that type, unless overridden again by the DASubscription attribute on any member. Similarly, in OPC Unified Architecture, use can specify the sampling interval using the UAMonitoring attribute, and it will be propagated further down.