It is unlikely that Lily is a lion. There is a very good chance that Mary got the football. There is a better than even chance that John went to the garden. It is probably not the case that if 'Lily is a lion' or 'Mary got the football' or both then Julius is a swan. There is little chance that if 'Mary got the football and Lily is a lion' then Jessica is a mouse. It is improbable that if 'Lily is a lion and John went to the garden' then Winona is a mouse.
There is a better than even chance that either 'Jessica is a mouse' or 'John went to the garden' but not both.
There is a better than even chance that either 'Jessica is a mouse' or 'John went to the garden' but not both.
Chances are slight that either 'Jessica is a mouse' or 'John went to the garden' 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.
  0.8::factB.
  0.6::factC.
  %hop1
  0.25::factX:-or(factA,factB).
  0.1::factY:-and(factB,factA).
  0.1::factZ:-and(factA,factC).

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

  query(conclusion).
  
Either 'Jessica is a mouse' or 'John went to the garden' but not both.