It is probably not the case that Julius is yellow. Chances are slight that Emily is a wolf. Chances are about even that Mary left the football. It is probably not the case that if 'Julius is yellow and Mary left the football' then Lily is a swan. Chances are about even that if either 'Julius is yellow' or 'Mary left the football' but not both then Greg is a frog. It is probably not the case that if 'Emily is a wolf and Mary left the football' then John grabbed the apple.
Chances are about even that either 'Greg is a frog' or 'Julius is yellow' but not both.
Chances are about even that either 'Greg is a frog' or 'Julius is yellow' but not both.
It is almost certain that either 'Greg is a frog' or 'Julius is yellow' but not 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
  0.25::factA.
  0.1::factB.
  0.5::factC.
  %hop1
  0.25::factX:-and(factA,factC).
  0.5::factY:-xor(factA,factC).
  0.25::factZ:-and(factB,factC).

  %hop2
  conclusion:-xor(factY,factA).

  query(conclusion).
  
Either 'Greg is a frog' or 'Julius is yellow' but not both.