We doubt that Julius is a frog. It is probably not the case that Fred put down the apple. It is improbable that Gertrude is a mouse. There is a better than even chance that if 'Julius is a frog and Fred put down the apple' then Greg is a swan. It is probably not the case that if 'Gertrude is a mouse' or 'Fred put down the apple' or both then Lily is yellow. It is certain that if 'Julius is a frog' or 'Gertrude is a mouse' or both then Mary moved to the garden.
It is probably not the case that 'Julius is a frog' or 'Gertrude is a mouse' or both.
It is probably not the case that 'Julius is a frog' or 'Gertrude is a mouse' or both.
It is probably the case that 'Julius is a frog' or 'Gertrude is a mouse' 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
  0.2::factA.
  0.25::factB.
  0.1::factC.
  %hop1
  0.6::factX:-and(factA,factB).
  0.25::factY:-or(factC,factB).
  1.0::factZ:-or(factA,factC).

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

  query(conclusion).
  
'Julius is a frog' or 'Gertrude is a mouse' or both.