There is a very good chance that Jessica is a wolf. There is almost no chance that Brian is a lion. It is certain that Bernhard is a swan. Chances are slight that if 'Bernhard is a swan' or 'Brian is a lion' or both then Julius is a rhino. It is highly likely that if either 'Brian is a lion' or 'Bernhard is a swan' but not both then Mary dropped the milk. It is certain that if 'Brian is a lion and Jessica is a wolf' then Fred is in the office.
There is a very good chance that 'Mary dropped the milk and Brian is a lion'.
It is impossible that 'Mary dropped the milk and Brian is a lion'.
There is a very good chance that 'Mary 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
  0.8::factA.
  0.02::factB.
  1.0::factC.
  %hop1
  0.1::factX:-or(factC,factB).
  0.9::factY:-xor(factB,factC).
  1.0::factZ:-and(factB,factA).

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

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