1. An analysis system ( 1 ) for analyzing at least one continuous query ( 100 ) for at least one input data stream ( 200 ), wherein the at least one input data stream ( 200 ) comprises a sequence of events captured by at least one sensor and wherein the analysis system comprises: a. an analyzer ( 10 ), adapted for executing the at least one continuous query ( 100 ) and at least one modified continuous query ( 100 ′) on the at least one input data stream ( 200 ), for comparing at least one output data stream ( 300 ) produced by the at least one continuous query ( 100 ) with at least one second output data stream ( 300 ′) produced by the at least one modified continuous query ( 100 ′) and for indicating at least one difference between the at least one output data stream ( 300 ) and the at least one second output data stream ( 300 ′); b. wherein the analyzer ( 10 ) is adapted for synchronizing the execution of the at least one continuous query ( 100 ) and the at least one modified continuous query ( 100 ′).