It is improbable that Julius is gray. It is probably not the case that Sandra left the football. It is almost certain that Greg is a frog. It is highly likely that if 'Sandra left the football and Greg is a frog' then Gertrude is a sheep. It is improbable that if 'Julius is gray' or 'Sandra left the football' or both then Mary dropped the milk. Chances are about even that if 'Greg is a frog' or 'Julius is gray' or both then Emily is a mouse.
Chances are about even that either 'Emily is a mouse' or 'Gertrude is a sheep' but not both.
Chances are about even that either 'Emily is a mouse' or 'Gertrude is a sheep' but not both.
It is highly unlikely that either 'Emily is a mouse' or 'Gertrude is a sheep' 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
  0.1::factA.
  0.25::factB.
  0.95::factC.
  %hop1
  0.9::factX:-and(factB,factC).
  0.1::factY:-or(factA,factB).
  0.5::factZ:-or(factC,factA).

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

  query(conclusion).
  
Either 'Emily is a mouse' or 'Gertrude is a sheep' but not both.