It is highly unlikely that Gertrude is a sheep. We doubt that Bernhard is green. It is almost certain that Mary left the milk. We doubt that if 'Mary left the milk' or 'Gertrude is a sheep' or both then John picked up the apple. There is a very good chance that if either 'Mary left the milk' or 'Gertrude is a sheep' but not both then Bill went to the office. It is certain that if either 'Gertrude is a sheep' or 'Mary left the milk' but not both then Lily is a frog.
It is almost certain that 'Lily is a frog' or 'Gertrude is a sheep' or both.
It is almost certain that 'Lily is a frog' or 'Gertrude is a sheep' or both.
Chances are slight that 'Lily is a frog' or 'Gertrude is a sheep' or both.

  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
  0.05::factA.
  0.2::factB.
  0.95::factC.
  %hop1
  0.2::factX:-or(factC,factA).
  0.8::factY:-xor(factC,factA).
  1.0::factZ:-xor(factA,factC).

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

  query(conclusion).
  
'Lily is a frog' or 'Gertrude is a sheep' or both.