There is a better than even chance that Greg is a lion. There is a very good chance that Mary got the football. It is probable that Lily is gray. There is a better than even chance that if 'Lily is gray' or 'Greg is a lion' or both then Yann is tired. It is certain that if 'Mary got the football and Greg is a lion' then John dropped the milk. It is improbable that if 'Lily is gray and Greg is a lion' then Brian is yellow.
It is highly unlikely that either 'Greg is a lion' or 'Brian is yellow' but not both.
There is a better than even chance that either 'Greg is a lion' or 'Brian is yellow' but not both.
It is highly unlikely that either 'Greg is a lion' or 'Brian is yellow' 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.
  0.8::factB.
  0.7::factC.
  %hop1
  0.6::factX:-or(factC,factA).
  1.0::factY:-and(factB,factA).
  0.1::factZ:-and(factC,factA).

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

  query(conclusion).
  
Either 'Greg is a lion' or 'Brian is yellow' but not both.