We believe that Fred went to the garden. We doubt that Julius is a swan. There is a very good chance that Greg is white. It is highly unlikely that if 'Greg is white and Julius is a swan' then Sandra left the apple. There is almost no chance that if 'Fred went to the garden' or 'Julius is a swan' or both then Brian is green. It is almost certain that if 'Julius is a swan and Greg is white' then Daniel dropped the milk.
It is improbable that 'Julius is a swan' or 'Greg is white' or both.
There is a very good chance that 'Julius is a swan' or 'Greg is white' or both.
It is improbable that 'Julius is a swan' or 'Greg is white' 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.
  0.2::factB.
  0.8::factC.
  %hop1
  0.05::factX:-and(factC,factB).
  0.02::factY:-or(factA,factB).
  0.95::factZ:-and(factB,factC).

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

  query(conclusion).
  
'Julius is a swan' or 'Greg is white' or both.