Removing duplicate items with setof

Q: setof(Child, Age ^ age(Child,Age), ChildList), 
   setof(Age, Child ^ age(Child,Age), AgeList).

A: ChildList = [ anne, pat, peter, tom ]
   AgeList = [5, 7, 8]

• Not only is duplicate removed, but list is also sorted
• Possible to combine objects within a program in other ways

Q: setof(Age/Child, age(Child,Age), List) 
A: List = [5/anne, 5/tom, 7/peter, 8/pat]

• bagof/3 is similar to setof/3 - and differs only in that the solution list is not sorted and may contain duplicates