-- | The outcome of comparing two items by possibly multiple contradicting
-- criteria.

  Dominates |

  -- | Where the second item is preferred by all used criteria

  -- | Where the items are equal by all used criteria

  StrongTie

  -- | Where each item is preferred by at least one criterion
  StrongTie |
  -- | Where the first item is preferred by all used critera
  Dominates

-- | Items which can be compared by possibly multiple criteria contradicting
-- criteria

-- | A collection of items where no item is preferred by all criteria.

-- | A series of 'Front's such that each subsequent 'Front' consists of
-- items for which some item in the previous front is preferable by all
-- criteria.

-- | Where two 'Front's are combined, all items are retained except those for
-- which at least one other item is preferred by all criteria.