Chances are about even that Brian is a frog. It is probably the case that Bernhard is a lion. It is highly likely that Gertrude is a mouse. It is certain that if 'Gertrude is a mouse' or 'Brian is a frog' or both then Sandra left the milk. It is probably not the case that if 'Bernhard is a lion' or 'Brian is a frog' or both then Julius is a swan. It is likely that if 'Brian is a frog and Bernhard is a lion' then John dropped the apple.
It is improbable that 'Gertrude is a mouse and Bernhard is a lion'.
There is a better than even chance that 'Gertrude is a mouse and Bernhard is a lion'.
It is improbable that 'Gertrude is a mouse and Bernhard 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.
  0.7::factB.
  0.9::factC.
  %hop1
  1.0::factX:-or(factC,factA).
  0.25::factY:-or(factB,factA).
  0.7::factZ:-and(factA,factB).

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

  query(conclusion).
  
'Gertrude is a mouse and Bernhard is a lion'.