There is little chance that Sandra dropped the milk. It is highly likely that Greg is white. We believe that Lily is a lion. There is a very good chance that if 'Sandra dropped the milk' or 'Greg is white' or both then Bernhard is a swan. There is a better than even chance that if either 'Lily is a lion' or 'Greg is white' but not both then Brian is yellow. It is highly unlikely that if 'Sandra dropped the milk and Lily is a lion' then John took the apple.
There is almost no chance that 'Sandra dropped the milk and Brian is yellow'.
There is almost no chance that 'Sandra dropped the milk and Brian is yellow'.
It is almost certain that 'Sandra dropped the milk and Brian is yellow'.

  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.
  0.9::factB.
  0.75::factC.
  %hop1
  0.8::factX:-or(factA,factB).
  0.6::factY:-xor(factC,factB).
  0.05::factZ:-and(factA,factC).

  %hop2
  conclusion:-and(factA,factY).

  query(conclusion).
  
'Sandra dropped the milk and Brian is yellow'.