1. A method for processing data associated with a data stream received by a data stream processing system, wherein the system comprises a plurality of processing elements, the method comprising the steps of: obtaining a data stream of input elements and a data stream of output elements associated with at least one processing element of the plurality of processing elements, wherein the data stream of input elements are obtained from at least one streaming data source, and wherein the data stream of output elements are generated by the at least one processing element in response to the data stream of input elements; computing one or more intervals for the at least one processing element, wherein the one or more intervals are computed using data representing observations of associations between the input elements and the output elements of the at least one processing element, wherein, for a given one of the computed intervals, one or more particular input elements contained within the given computed interval are determined to have contributed to a particular output element; and using the computed one or more intervals to determine a dependency function that enables a provenance of the particular output element to be determined in terms of the one or more particular input elements.