It is certain that Gertrude is a wolf. We doubt that Sandra got the milk. It is probably the case that Emily is a mouse. Chances are slight that if either 'Gertrude is a wolf' or 'Emily is a mouse' but not both then Julius is a lion. It is highly unlikely that if 'Emily is a mouse and Sandra got the milk' then Brian is green. It is unlikely that if 'Sandra got the milk' or 'Emily is a mouse' or both then Greg is a frog.
It is certain that 'Gertrude is a wolf and Greg is a frog'.
It is unlikely that 'Gertrude is a wolf and Greg is a frog'.
It is certain that 'Gertrude is a wolf and Greg is a frog'.

  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
  1.0::factA.
  0.2::factB.
  0.7::factC.
  %hop1
  0.1::factX:-xor(factA,factC).
  0.05::factY:-and(factC,factB).
  0.2::factZ:-or(factB,factC).

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

  query(conclusion).
  
'Gertrude is a wolf and Greg is a frog'.