We doubt that Julius is gray. It is likely that John dropped the apple. It is almost certain that Gertrude is a wolf. We doubt that if either 'John dropped the apple' or 'Gertrude is a wolf' but not both then Mary moved to the office. We believe that if 'Julius is gray' or 'Gertrude is a wolf' or both then Bernhard is a frog. It is almost certain that if either 'John dropped the apple' or 'Gertrude is a wolf' but not both then Greg is a swan.
It is highly unlikely that 'Greg is a swan and Mary moved to the office'.
It is highly unlikely that 'Greg is a swan and Mary moved to the office'.
There is a better than even chance that 'Greg is a swan and Mary moved to the office'.

  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.
  0.7::factB.
  0.95::factC.
  %hop1
  0.2::factX:-xor(factB,factC).
  0.75::factY:-or(factA,factC).
  0.95::factZ:-xor(factB,factC).

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

  query(conclusion).
  
'Greg is a swan and Mary moved to the office'.