Chances are slight that Greg is gray. We doubt that Brian is a swan. We believe that Daniel dropped the milk. It is almost certain that if 'Brian is a swan' or 'Daniel dropped the milk' or both then Sumit is thirsty. It is highly likely that if 'Greg is gray and Brian is a swan' then Gertrude is a sheep. There is little chance that if 'Greg is gray' or 'Daniel dropped the milk' or both then John went to the office.
It is likely that 'Daniel dropped the milk and Sumit is thirsty'.
It is likely that 'Daniel dropped the milk and Sumit is thirsty'.
It is highly unlikely that 'Daniel dropped the milk and Sumit is thirsty'.

  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
  0.1::factA.
  0.2::factB.
  0.75::factC.
  %hop1
  0.95::factX:-or(factB,factC).
  0.9::factY:-and(factA,factB).
  0.1::factZ:-or(factA,factC).

  %hop2
  conclusion:-and(factC,factX).

  query(conclusion).
  
'Daniel dropped the milk and Sumit is thirsty'.