There is little chance that Bernhard is yellow. It is improbable that Greg is gray. Chances are about even that Julius is white. There is almost no chance that if 'Bernhard is yellow' or 'Greg is gray' or both then Mary left the football. There is a better than even chance that if either 'Julius is white' or 'Bernhard is yellow' but not both then Brian is yellow. It is probable that if 'Julius is white' or 'Greg is gray' or both then John went to the garden.
There is a better than even chance that 'Bernhard is yellow' or 'Mary left the football' or both.
Chances are slight that 'Bernhard is yellow' or 'Mary left the football' or both.
There is a better than even chance that 'Bernhard is yellow' or 'Mary left the football' 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.
  0.1::factB.
  0.5::factC.
  %hop1
  0.02::factX:-or(factA,factB).
  0.6::factY:-xor(factC,factA).
  0.7::factZ:-or(factC,factB).

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

  query(conclusion).
  
'Bernhard is yellow' or 'Mary left the football' or both.