1. A computer-implemented method, comprising: providing a plurality of processing elements comprising one or more operators, the operators configured to process streaming data tuples; establishing an operator graph of a plurality of operators, the operator graph defining at least one execution path in which a first operator of the plurality of operators is configured to: (i) receive data tuples from at least one upstream operator and (ii) transmit data tuples to at least one downstream operator; defining a windowing condition specifying at least one rule for processing data tuples; and responsive to receiving, at a first operator of the plurality of operators, an indication to enforce the windowing condition on the first operator: processing a first set of data tuples received by the first operator; and while processing the first set of data tuples, upon determining that the windowing condition has been satisfied and by operation of one or more computer processors: ceasing the processing of the first set of data tuples, wherein at least one data tuple of the first set of data tuples is not processed; and processing a second set of data tuples.