A test battery is proposed that can be used to characterize the behavi
our of updating systems. The battery is based on 20 rationality postul
ates of the types developed in studies of theory change and nonmonoton
ic reasoning. These postulates are arranged into seven sequences with
increasing strength, each of which measures the degree of conformity w
ith a basic desideratum for database updating. Some of these desiderat
a are partly in conflict, and they cannot all be satisfied to the high
est degree. Mathematical characterizations are given of how far they c
an be combined.