Allow recording of an action where the date is unknown - required for feeder systems which have this data.
I would support this + I wonder if this might/should be coupled with some additional state value such as 'reported' which makes it clear that this is a historical record, capturing the clinical content but for which the state is unknown or unreliable.
Rather than having a null date, would it not be better to have something like a flag that means 'on or prior to', and/or ian's suggestion of marking the date as 'imported/reported'.
The point is that we just don't have a date, so rather than synthesising one and marking it as unreliable we should allow null and indicate why it is null. I guess this is a case where null-flavour on DataValue would have been useful.
What are the consequences for null dates in Actions in querying?
if we don't even include a reference date (e.g. date of import) as the most recent possible date, then we can have an Action with a null date that is created on 1/1/2012, and retrieved in a query looking for 'recent actions' 5 years later, if the query is not smart enough to know that null dates should be completely ignored. Also, a query that looks for all Actions before 1/1/2015 should find this Action created on 1/1/2012, but might not if it doesn't know any date at all for the Action.