Chances are about even that Brian is a frog. It is probable that Greg is white. It is certain that Mary left the milk. Chances are slight that if 'Brian is a frog' or 'Mary left the milk' or both then Antoine is hungry. There is a very good chance that if either 'Greg is white' or 'Brian is a frog' but not both then Julius is a rhino. It is probable that if either 'Mary left the milk' or 'Brian is a frog' but not both then John got the apple.
It is probably not the case that 'Greg is white and Brian is a frog'.
It is probably not the case that 'Greg is white and Brian is a frog'.
It is probably the case that 'Greg is white and Brian is a frog'.

  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
  0.5::factA.
  0.7::factB.
  1.0::factC.
  %hop1
  0.1::factX:-or(factA,factC).
  0.8::factY:-xor(factB,factA).
  0.7::factZ:-xor(factC,factA).

  %hop2
  conclusion:-and(factB,factA).

  query(conclusion).
  
'Greg is white and Brian is a frog'.