We doubt that Greg is gray. It is impossible that Bill went to the bedroom. It is probable that Julius is a rhino. Chances are about even that if 'Julius is a rhino and Greg is gray' then Jason is tired. It is likely that if 'Julius is a rhino and Greg is gray' then Brian is a swan. It is certain that if either 'Bill went to the bedroom' or 'Greg is gray' but not both then John left the apple.
We doubt that 'Julius is a rhino' or 'Greg is gray' or both.
We believe that 'Julius is a rhino' or 'Greg is gray' or both.
We doubt that 'Julius is a rhino' or 'Greg is gray' 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.
  0.0::factB.
  0.7::factC.
  %hop1
  0.5::factX:-and(factC,factA).
  0.7::factY:-and(factC,factA).
  1.0::factZ:-xor(factB,factA).

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

  query(conclusion).
  
'Julius is a rhino' or 'Greg is gray' or both.