There are a number of validation considerations for calculating attribution periods. One consideration is whether or not evidence can have a null attribution end date. If all records for an evidence type should be attributed to finite periods, then a validation should be added to prevent a null attribution end date.
Another consideration is whether or not gaps are allowed between attribution periods. If there should be no gaps, then validation should be added to ensure these gaps do not occur. Also, validations can be used to ensure that attribution periods do not overlap.