module sets

-- each signature represents a set

sig ABCD {}

-- sig ABD in ABCD {}

sig ABC in ABCD {}

sig AB in ABCD {}

sig AC in ABC {}

sig A in ABC {}

--sig BD in ABD {}
sig BD in ABCD {}

sig B in ABCD {}

fact {
        B in AB
        B in BD
        A in AB
        A in AC
--      AB in ABD
        AB in ABC
--      ABCD in ABC + ABD
        ABCD in BD + ABC
        ABC in AB + AC
--      ABD in AB + BD
}

run {} for 2