Sensitivity Analysis for Declarative Relational Query Languages with   Ordinal Ranks
  We present sensitivity analysis for results of query executions in a relational model of data extended by ordinal ranks. The underlying model of data results from the ordinary Codd's model of data in which we consider ordinal ranks of tuples in data tables expressing degrees to which tuples match queries. In this setting, we show that ranks assigned to tuples are insensitive to small changes, i.e., small changes in the input data do not yield large changes in the results of queries. 
Radim Belohlavek, Lucie Urbanova, Vilem Vychodil
cs.DB