It is improbable that John moved to the office. Chances are about even that Sandra left the milk. We doubt that Bernhard is a rhino. It is impossible that if 'Bernhard is a rhino' or 'John moved to the office' or both then Greg is a frog. It is highly likely that if either 'John moved to the office' or 'Bernhard is a rhino' but not both then Daniel got the apple. It is unlikely that if either 'Sandra left the milk' or 'Bernhard is a rhino' but not both then Lily is a swan.
It is likely that 'Lily is a swan' or 'Greg is a frog' or both.
Chances are slight that 'Lily is a swan' or 'Greg is a frog' or both.
It is likely that 'Lily is a swan' or 'Greg is a frog' 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
  0.1::factA.
  0.5::factB.
  0.2::factC.
  %hop1
  0.0::factX:-or(factC,factA).
  0.9::factY:-xor(factA,factC).
  0.2::factZ:-xor(factB,factC).

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

  query(conclusion).
  
'Lily is a swan' or 'Greg is a frog' or both.