We doubt that Brian is green. There is little chance that Julius is a rhino. It is improbable that John went to the bedroom. It is probably not the case that if 'Julius is a rhino' or 'John went to the bedroom' or both then Jason is tired. There is almost no chance that if 'Julius is a rhino' or 'John went to the bedroom' or both then Bernhard is a frog. Chances are slight that if 'Julius is a rhino' or 'John went to the bedroom' or both then Jeff discarded the milk.
It is probably not the case that either 'Julius is a rhino' or 'Brian is green' but not both.
It is probably not the case that either 'Julius is a rhino' or 'Brian is green' but not both.
It is probable that either 'Julius is a rhino' or 'Brian 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
  0.2::factA.
  0.1::factB.
  0.1::factC.
  %hop1
  0.25::factX:-or(factB,factC).
  0.02::factY:-or(factB,factC).
  0.1::factZ:-or(factB,factC).

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

  query(conclusion).
  
Either 'Julius is a rhino' or 'Brian is green' but not both.