Chances are about even that Greg is a frog. It is certain that Lily is a lion. It is probably not the case that Mary went to the office. It is highly unlikely that if either 'Lily is a lion' or 'Mary went to the office' but not both then Fred left the apple. We believe that if 'Mary went to the office and Greg is a frog' then Julius is white. It is improbable that if 'Greg is a frog and Mary went to the office' then Bernhard is a swan.
There is almost no chance that 'Bernhard is a swan and Lily is a lion'.
There is almost no chance that 'Bernhard is a swan and Lily is a lion'.
Chances are about even that 'Bernhard is a swan and Lily 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
  0.5::factA.
  1.0::factB.
  0.25::factC.
  %hop1
  0.05::factX:-xor(factB,factC).
  0.75::factY:-and(factC,factA).
  0.1::factZ:-and(factA,factC).

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

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