There is almost no chance that John dropped the apple. It is probable that Julius is a frog. There is a better than even chance that Bill went to the office. Chances are about even that if either 'John dropped the apple' or 'Bill went to the office' but not both then Bernhard is yellow. It is impossible that if 'John dropped the apple' or 'Bill went to the office' or both then Jason is thirsty. It is probably the case that if either 'Bill went to the office' or 'John dropped the apple' but not both then Sandra left the football.
It is improbable that 'Bill went to the office' or 'Julius is a frog' or both.
It is highly likely that 'Bill went to the office' or 'Julius is a frog' or both.
It is improbable that 'Bill went to the office' or 'Julius 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
  0.02::factA.
  0.7::factB.
  0.6::factC.
  %hop1
  0.5::factX:-xor(factA,factC).
  0.0::factY:-or(factA,factC).
  0.7::factZ:-xor(factC,factA).

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

  query(conclusion).
  
'Bill went to the office' or 'Julius is a frog' or both.