It is highly likely that Emily is a mouse. It is certain that Bernhard is yellow. It is unlikely that Lily is a swan. Chances are about even that if 'Bernhard is yellow and Lily is a swan' then Julius is a swan. There is little chance that if 'Emily is a mouse' or 'Lily is a swan' or both then Mary went to the bedroom. It is unlikely that if 'Lily is a swan' or 'Emily is a mouse' or both then John discarded the apple.
There is a very good chance that either 'Julius is a swan' or 'Emily is a mouse' but not both.
There is a very good chance that either 'Julius is a swan' or 'Emily is a mouse' but not both.
We doubt that either 'Julius is a swan' or 'Emily is a mouse' 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
  0.9::factA.
  1.0::factB.
  0.2::factC.
  %hop1
  0.5::factX:-and(factB,factC).
  0.1::factY:-or(factA,factC).
  0.2::factZ:-or(factC,factA).

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

  query(conclusion).
  
Either 'Julius is a swan' or 'Emily is a mouse' but not both.