It is unlikely that John went to the hallway. It is certain that Gertrude is a mouse. Chances are slight that Lily is a rhino. Chances are slight that if 'John went to the hallway' or 'Gertrude is a mouse' or both then Greg is white. There is a very good chance that if 'Lily is a rhino' or 'Gertrude is a mouse' or both then Emily is a sheep. We doubt that if 'John went to the hallway' or 'Gertrude is a mouse' or both then Bernhard is yellow.
It is highly likely that either 'Gertrude is a mouse' or 'Lily is a rhino' but not both.
It is highly likely that either 'Gertrude is a mouse' or 'Lily is a rhino' but not both.
Chances are slight that either 'Gertrude is a mouse' or 'Lily is a rhino' 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
  0.2::factA.
  1.0::factB.
  0.1::factC.
  %hop1
  0.1::factX:-or(factA,factB).
  0.8::factY:-or(factC,factB).
  0.2::factZ:-or(factA,factB).

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

  query(conclusion).
  
Either 'Gertrude is a mouse' or 'Lily is a rhino' but not both.