There is a better than even chance that Brian is yellow. It is probably not the case that Mary dropped the milk. It is certain that Julius is gray. It is probably the case that if either 'Julius is gray' or 'Brian is yellow' but not both then Fred went to the office. It is probable that if 'Brian is yellow' or 'Julius is gray' or both then Jason is tired. It is probable that if 'Mary dropped the milk' or 'Julius is gray' or both then John moved to the garden.
It is certain that 'Brian is yellow' or 'Julius is gray' or both.
It is certain that 'Brian is yellow' or 'Julius is gray' or both.
Chances are slight that 'Brian is yellow' or 'Julius is gray' 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
  0.6::factA.
  0.25::factB.
  1.0::factC.
  %hop1
  0.7::factX:-xor(factC,factA).
  0.7::factY:-or(factA,factC).
  0.7::factZ:-or(factB,factC).

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

  query(conclusion).
  
'Brian is yellow' or 'Julius is gray' or both.