Equivalence of Histories
Two operations conflict if their execution order affects their return values or the DB state.
- a read and write on the same data item conflict
- two writes on the same data item conflict
- two reads (on the same data item) do not conflict
Two histories are equivalent if they have the same operations and conflicting operations are in the same order in both histories
- because only the relative order of conflicting operations can affect the result of the histories