It is probably not the case that Lily is a frog. It is probably not the case that Fred dropped the milk. There is little chance that Bernhard is white. It is almost certain that if 'Lily is a frog' or 'Bernhard is white' or both then Greg is a frog. It is unlikely that if either 'Bernhard is white' or 'Lily is a frog' but not both then Mary is in the school. Chances are slight that if either 'Bernhard is white' or 'Fred dropped the milk' but not both then Jeff moved to the garden.
Chances are about even that 'Lily is a frog' or 'Fred dropped the milk' or both.
Chances are about even that 'Lily is a frog' or 'Fred dropped the milk' or both.
It is almost certain that 'Lily is a frog' or 'Fred dropped the milk' 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
  0.25::factA.
  0.25::factB.
  0.1::factC.
  %hop1
  0.95::factX:-or(factA,factC).
  0.2::factY:-xor(factC,factA).
  0.1::factZ:-xor(factC,factB).

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

  query(conclusion).
  
'Lily is a frog' or 'Fred dropped the milk' or both.