It is unlikely that Greg is green. It is probably the case that John moved to the garden. We believe that Mary dropped the apple. There is a very good chance that if 'Greg is green' or 'John moved to the garden' or both then Julius is yellow. It is probably not the case that if 'John moved to the garden and Greg is green' then Gertrude is a wolf. It is probably the case that if either 'Mary dropped the apple' or 'Greg is green' but not both then Lily is white.
There is a better than even chance that 'Julius is yellow' or 'Greg is green' or both.
There is a better than even chance that 'Julius is yellow' or 'Greg is green' or both.
It is highly unlikely that 'Julius is yellow' or 'Greg is green' 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.
  0.7::factB.
  0.75::factC.
  %hop1
  0.8::factX:-or(factA,factB).
  0.25::factY:-and(factB,factA).
  0.7::factZ:-xor(factC,factA).

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

  query(conclusion).
  
'Julius is yellow' or 'Greg is green' or both.