There is a better than even chance that Bernhard is a rhino. Chances are slight that John got the apple. There is a better than even chance that Brian is a frog. There is a very good chance that if 'Bernhard is a rhino' or 'Brian is a frog' or both then Mary took the milk. It is highly unlikely that if 'John got the apple' or 'Bernhard is a rhino' or both then Greg is a swan. It is unlikely that if either 'John got the apple' or 'Bernhard is a rhino' but not both then Emily is a mouse.
It is probable that either 'Emily is a mouse' or 'John got the apple' but not both.
We doubt that either 'Emily is a mouse' or 'John got the apple' but not both.
It is probable that either 'Emily is a mouse' or 'John got the apple' 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
  0.6::factA.
  0.1::factB.
  0.6::factC.
  %hop1
  0.8::factX:-or(factA,factC).
  0.05::factY:-or(factB,factA).
  0.2::factZ:-xor(factB,factA).

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

  query(conclusion).
  
Either 'Emily is a mouse' or 'John got the apple' but not both.