This works similar to how PatientView operates now. Most of the record is re-sent each time with the exception of the LabOrders, Observations and Procedures sections.
Within these nodes Start and End date attributes can be supplied to indicate that the sections only contain the part of the patients record that falls between those two dates.
If the attributes are supplied then any items of that type that have been received from the unit between those dates are deleted before the items received in the file are loaded.
The date span should be wide enough to cover the longest typical period between an activity (such as a blood sample being taken) and the data being loaded on the system (such as when the result is returned from the lab).
The date values used should be the date range which was used by the extraction tool when querying the database and NOT the earliest and latest dates of items it found. The later behaviour is seen in some current PV feeds.