It is probable that Bernhard is a rhino. We doubt that Jason is tired. There is a better than even chance that Brian is white. Chances are slight that if 'Bernhard is a rhino and Jason is tired' then Greg is a swan. It is impossible that if either 'Jason is tired' or 'Bernhard is a rhino' but not both then Mary went to the bedroom. It is unlikely that if 'Bernhard is a rhino' or 'Brian is white' or both then John moved to the garden.
It is highly unlikely that either 'Brian is white' or 'Greg is a swan' but not both.
There is a better than even chance that either 'Brian is white' or 'Greg is a swan' but not both.
It is highly unlikely that either 'Brian is white' or 'Greg is a swan' 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
  0.7::factA.
  0.2::factB.
  0.6::factC.
  %hop1
  0.1::factX:-and(factA,factB).
  0.0::factY:-xor(factB,factA).
  0.2::factZ:-or(factA,factC).

  %hop2
  conclusion:-xor(factC,factX).

  query(conclusion).
  
Either 'Brian is white' or 'Greg is a swan' but not both.