The Boeing 737 was tracking towards Sydney at about 250 kts, descending through 6000 ft, following a Boeing 747, when the crew of the 737 reported that they suddenly encountered wake turbulence. The aircraft abruptly rolled about 30 degrees to the left before the handling pilot was able to return the aircraft to straight and level. The crew advised ATC that they required greater separation from the 747. No passengers were injured, however the purser cut her arm and the second senior flight attendant grazed her knee, when they fell during the occurrence. Subsequent investigation revealed that the 737 was 5.8 NM behind and 600 ft below the 747 at the time of the occurrence. The 737 had rolled 38.1 degrees to the left before the roll was stopped. The minimum longitudinal separation standard required for wake turbulence avoidance was 5 NM.