Elimination of intersection anomalies from database schemes

The desirability of acyclic (conflict-free) schemes is well argued in [8] and [13]. When a scheme is described by multivalued dependencies, acyclicity means that the dependencies do not split each other's left-hand side and do not form intersection anomalies. It is shown that if the second condition fails to hold, the scheme can be amended so that it does hold. The basic step is to add one attribute and some dependencies to resolve one intersection anomaly. This step generates an extension of the given scheme in which the anomaly does not exist. Also, the iterative use of the basic step is analyzed and it is proved that the transformation so defined terminates and removes all intersection anomalies.