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; providing a selected first trace record by 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 selected first trace record's existence depends, wherein the second set of trace records is a subset of the first set of trace records and the second set of trace records represents a chain of causality of events leading up to an event represented by the selected first trace record; 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, thereby enabling tracing of one or more events that caused the selected first trace record to come into existence during the course of dataflow program execution, displaying, as part of a graphical user interface, one or more actors and one or more actor connections defined by the dataflow program; and displaying, as part of the graphical user interface, a depiction of the selected first trace record in closer proximity to a related one of the displayed actor connections than to all other displayed actor connections, wherein the selected first trace record represents a token that, during execution of the dataflow program, was produced to or consumed from the related actor connection.