The document describes a method for calculating the probability of an Reactive Constraint (RCon) specification being satisfied, violated, or unaffected given a trace or log of event data. An RCon consists of an activation formula (φα) and target formula (φτ). The probability of a single RCon is calculated by determining the maximum likelihood estimate of the target formula occurring given the activation occurred, based on event labellings in the traces. The probability of an RCon specification (a set of RCon rules) is also defined based on the probabilities of individual RCon rules. This allows interestingness measures to be applied to entire specifications rather than just individual rules.