13. One or more computer-readable storage media according to claim 12 , wherein when a fact is logically deleted it is automatically removed from the first table and automatically added to the second table and a corresponding valid-to time value is added to the logically deleted fact, the logically deleted fact including a same valid-from time value that it had when it was stored in the first table.
14. One or more computer-readable storage media according to claim 13 , wherein the first table has a valid-from column that stores the valid-from time value of the logically deleted fact, and wherein the second table has a valid-from column that stores the valid-from time value of the logically deleted record and has a valid-to column that stores the valid-to time value of the logically deleted record.