It is impossible that Emily is a mouse. It is improbable that Brian is yellow. It is likely that John dropped the apple. We believe that if either 'John dropped the apple' or 'Brian is yellow' but not both then Mary went to the garden. We believe that if 'Emily is a mouse' or 'Brian is yellow' or both then Bernhard is a swan. We believe that if either 'Brian is yellow' or 'John dropped the apple' but not both then Julius is a rhino.
Chances are about even that 'Julius is a rhino' or 'Emily is a mouse' or both.
Chances are about even that 'Julius is a rhino' or 'Emily is a mouse' or both.
It is impossible that 'Julius is a rhino' or 'Emily is a mouse' or 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
  0.0::factA.
  0.1::factB.
  0.7::factC.
  %hop1
  0.75::factX:-xor(factC,factB).
  0.75::factY:-or(factA,factB).
  0.75::factZ:-xor(factB,factC).

  %hop2
  conclusion:-or(factZ,factA).

  query(conclusion).
  
'Julius is a rhino' or 'Emily is a mouse' or both.