With deferred mapping, the mapped node object does not have to exist at the time of mapping, but is determined later, when it is actually needed. This is useful e.g. if it is costly to create the full object graph upfront, either because it is very large, or because it depends on dynamic factors that are not known at the time of mapping.

In order to use deferred mapping, you need to:

1. Specify Deferred = true with the DANode or UANode attribute. This causes the mapped member be set to a function (“deferred mapping function”) that returns the mapped object (normally, the mapped member contains the mapped object itself).
2. Set the DeferredMapNodeFunction of the  DAClientMapper or  UAClientMapper to a function that returns the deferred mapping function (see above) for a given mapping context.

The deferred mapping is used in OPC-UA Modelling to dynamically provide node objects whose types depend on the information model of the OPC-UA server.