Chances are slight that Lily is green. It is unlikely that Bill left the football. It is certain that Fred went to the garden. It is likely that if either 'Fred went to the garden' or 'Bill left the football' but not both then Mary moved to the office. Chances are slight that if either 'Lily is green' or 'Fred went to the garden' but not both then Bernhard is gray. Chances are slight that if 'Bill left the football and Fred went to the garden' then Greg is green.
There is a very good chance that either 'Bernhard is gray' or 'Greg is green' but not both.
There is little chance that either 'Bernhard is gray' or 'Greg is green' but not both.
There is a very good chance that either 'Bernhard is gray' or 'Greg is green' 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
  0.1::factA.
  0.2::factB.
  1.0::factC.
  %hop1
  0.7::factX:-xor(factC,factB).
  0.1::factY:-xor(factA,factC).
  0.1::factZ:-and(factB,factC).

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

  query(conclusion).
  
Either 'Bernhard is gray' or 'Greg is green' but not both.