  Added value can be extracted from event logs generated by business processes
in various ways. However, although complex computations can be performed over
event logs, the result of such computations is often difficult to explain; in
particular, it is hard to determine what parts of an input log actually matters
in the production of that result. This paper describes how an existing log
processing library, called BeepBeep, can be extended in order to provide a form
of provenance: individual output events produced by a query can be precisely
traced back to the data elements of the log that contribute to (i.e. "explain")
the result.
