It is highly likely that Bernhard is gray. It is highly likely that Sandra dropped the milk. We doubt that Julius is white. There is little chance that if 'Sandra dropped the milk' or 'Julius is white' or both then Bill moved to the office. There is little chance that if 'Julius is white' or 'Bernhard is gray' or both then Brian is a lion. There is a better than even chance that if 'Bernhard is gray and Julius is white' then Mary went to the garden.
There is little chance that 'Sandra dropped the milk and Brian is a lion'.
There is little chance that 'Sandra dropped the milk and Brian is a lion'.
There is a better than even chance that 'Sandra dropped the milk and Brian is a lion'.

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

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

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