It is probably not the case that Greg is a rhino. It is improbable that Gertrude is a cat. There is little chance that Jason is tired. Chances are slight that if 'Gertrude is a cat' or 'Greg is a rhino' or both then Lily is green. There is almost no chance that if 'Greg is a rhino' or 'Gertrude is a cat' or both then Bernhard is yellow. It is likely that if 'Greg is a rhino' or 'Jason is tired' or both then John went to the garden.
It is improbable that either 'Bernhard is yellow' or 'Gertrude is a cat' but not both.
It is improbable that either 'Bernhard is yellow' or 'Gertrude is a cat' but not both.
It is likely that either 'Bernhard is yellow' or 'Gertrude is a cat' 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
  0.25::factA.
  0.1::factB.
  0.1::factC.
  %hop1
  0.1::factX:-or(factB,factA).
  0.02::factY:-or(factA,factB).
  0.7::factZ:-or(factA,factC).

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

  query(conclusion).
  
Either 'Bernhard is yellow' or 'Gertrude is a cat' but not both.