It is probable that Greg is green. It is probably the case that Julius is gray. It is probably the case that Brian is a lion. It is unlikely that if 'Greg is green' or 'Julius is gray' or both then Lily is yellow. We believe that if 'Julius is gray' or 'Brian is a lion' or both then Mary dropped the milk. There is a better than even chance that if either 'Greg is green' or 'Brian is a lion' but not both then John moved to the office.
It is impossible that 'Mary dropped the milk' or 'Brian is a lion' or both.
It is highly likely that 'Mary dropped the milk' or 'Brian is a lion' or both.
It is impossible that 'Mary dropped the milk' or 'Brian is a lion' or both.

  and(A,B) :- A,B.
  or(A,B) :- A;B.
  nand(A,B) :- not(and(A,B)).
  nor(A,B) :- not(or(A,B)).
  xor(A,B) :- or(A,B), nand(A,B).

  %hop0
  0.7::factA.
  0.7::factB.
  0.7::factC.
  %hop1
  0.2::factX:-or(factA,factB).
  0.75::factY:-or(factB,factC).
  0.6::factZ:-xor(factA,factC).

  %hop2
  conclusion:-or(factY,factC).

  query(conclusion).
  
'Mary dropped the milk' or 'Brian is a lion' or both.