It is probably the case that Bernhard is a lion. There is almost no chance that John went to the hallway. It is probably the case that Brian is a swan. It is almost certain that if either 'Brian is a swan' or 'Bernhard is a lion' but not both then Sandra dropped the milk. It is impossible that if either 'Brian is a swan' or 'John went to the hallway' but not both then Fred moved to the office. We believe that if 'Bernhard is a lion' or 'John went to the hallway' or both then Mary put down the apple.
It is highly unlikely that 'Bernhard is a lion and Brian is a swan'.
Chances are about even that 'Bernhard is a lion and Brian is a swan'.
It is highly unlikely that 'Bernhard is a lion and Brian is a swan'.

  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.
  0.02::factB.
  0.7::factC.
  %hop1
  0.95::factX:-xor(factC,factA).
  0.0::factY:-xor(factC,factB).
  0.75::factZ:-or(factA,factB).

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

  query(conclusion).
  
'Bernhard is a lion and Brian is a swan'.