P1 [A------B-------C--------D-------E]
P2         [1-----2--------3]

A: P1 starts working
B: User wants a report, so P1 spawns job P2.  P1 now waits.....
C: P1 detects that the .TXT file is ready, so it resumes working
D: P1 detects that the .XLS file is ready, so it reports "succeeded"
E: P1 ends

1: P2 starts and begins work on the .TXT report
2: P2 finishes the .TXT report and begins work on the .XLS report
3: P2 completes the .XLS report and ends.