Chances are slight that Julius is gray. There is a very good chance that Jason is tired. It is probably the case that Mary took the football. We believe that if either 'Mary took the football' or 'Julius is gray' but not both then Bernhard is white. It is unlikely that if either 'Julius is gray' or 'Mary took the football' but not both then John put down the milk. There is little chance that if either 'Mary took the football' or 'Julius is gray' but not both then Emily is a mouse.
We doubt that 'Bernhard is white' or 'Jason is tired' or both.
It is highly likely that 'Bernhard is white' or 'Jason is tired' or both.
We doubt that 'Bernhard is white' or 'Jason is tired' 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
  0.1::factA.
  0.8::factB.
  0.7::factC.
  %hop1
  0.75::factX:-xor(factC,factA).
  0.2::factY:-xor(factA,factC).
  0.1::factZ:-xor(factC,factA).

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

  query(conclusion).
  
'Bernhard is white' or 'Jason is tired' or both.