1. A method of processing data sets in a pipelined stream processor; the processor having a pipelined data path; the pipeline including at least one input, at least one output, and at least one discrete stage; the pipeline configured to enable one or more data sets each comprising one or more data items to be streamed therethrough; wherein, in use, said data items enter said pipeline from the at least one input, propagate through said pipeline, and exit said pipeline through the at least one output, the or each discrete stage representing an operation to be performed on the data item occupying said discrete stage; the method comprising: defining one or more non-overlapping sections of said pipeline corresponding to portions of said pipeline occupied by the data items of one of the at least one data sets; providing one or more logic units each dedicated to control the progress of the data items of one of the at least one data sets through said pipeline as said section advances through said pipeline.