[Health-dev] Cannot overwrite a previously saved data

[Hannah Sun]

Hi! I would just want to ask whether [1]it is possible for a previous record 
that is saved to be a read-only (meaning it cannot be written again). 

For example, in the patient evaluation, once a doctor was done in evaluating 
and saved it, it cannot be overwritten again. 

Additional question,[2] is it possible that the data is time-bound( meaning 
those records that are 1 day older cannot be overwritten anymore) but those who 
are less than a day can still be overwritten?

 This is  to ensure that patient data especially those taken a long time ago 
would not be easily manipulated. 

How can we implement this? Thank you!