We believe that Lily is a swan. It is highly unlikely that Gertrude is a cat. We believe that John got the apple. It is highly likely that if either 'Gertrude is a cat' or 'Lily is a swan' but not both then Jeff left the apple. It is probably not the case that if 'Lily is a swan and Gertrude is a cat' then Sumit is bored. Chances are about even that if either 'Lily is a swan' or 'John got the apple' but not both then Julius is yellow.
It is highly unlikely that 'Gertrude is a cat' or 'Jeff left the apple' or both.
It is probable that 'Gertrude is a cat' or 'Jeff left the apple' or both.
It is highly unlikely that 'Gertrude is a cat' or 'Jeff left the apple' 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
  0.75::factA.
  0.05::factB.
  0.75::factC.
  %hop1
  0.9::factX:-xor(factB,factA).
  0.25::factY:-and(factA,factB).
  0.5::factZ:-xor(factA,factC).

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

  query(conclusion).
  
'Gertrude is a cat' or 'Jeff left the apple' or both.