9. One or more computer-readable storage media according to claim 8 , wherein each logically deleted fact, having at one time been added, includes a valid-from time value corresponding to when it was added to the semantic data store.
9. One or more computer-readable storage media according to claim 8 , wherein each logically deleted fact, having at one time been added, includes a valid-from time value corresponding to when it was added to the semantic data store. 10. One or more computer-readable storage media according to claim 9 , wherein each fact that has not been logically deleted has no valid-to time value, whereby some facts are currently valid as indicated by their lack of a valid-to time value and some facts are currently invalid as indicated by their having a valid-to time value, such that over time the facts that are valid and invalid changes, some becoming invalid.