The Post-filter Association Processor only exists on the Publisher Channel and receives events from the Sync & Ignore Publisher Filter.
Depending on certain criteria the Post-filter Association Processor will take one of the following actions:
The Synthetic Add Process on the Publisher channel happens in the Post-filter Association Processor.
The Synthetic Add Process query back to the source data store for all attributes listed in the driver filter for the current object's class.
The Synthetic Add process then builds an <add> document with those attribute values and discards the original <modify> or <sync> event.