The Outer Planets was a collective term. Its exact subject is difficult to determine. The term Outer Worlds was also in common use. It is unclear what, if any, difference exists between the two. It has been suggested that the Outer and Inner Worlds were under direct Federation control with the Outer Planets being independent and autonomous. While it is true that Servalan specifically refers to Sarran as an Outer Planet, and it does seem to be independent, on other occasions the family of Blake are variously described as relocating to either the Outer Worlds or Outer Planets depending on who is speaking, with no apparent difference in meaning. The two terms would here seem to be used interchangeably.