1. A method of processing a dataflow program that defines one or more actors and one or more connections, wherein each connection passes a token from an output port of any one of the actors to an input port of any one of the actors, the method comprising: causing one or more processors to access and execute instructions of the dataflow program; as instructions of the dataflow program are being executed, creating a first set of trace records that represents a sequence of events, wherein each event is a token production by an actor, a token consumption by an actor, an actor state change, or an actor action firing; displaying information representative of a first subset of trace records from the first set of trace records; selecting a first trace record from the first subset of trace records; processing the first set of trace records to identify, based on definitions specified by the dataflow program, a second set of trace records from which the first trace record's existence depends; and displaying information representative of a second subset of trace records, wherein the second subset of trace records is a subset of the second set of trace records.