It is improbable that Lily is yellow. There is almost no chance that Jessica is a mouse. It is probably the case that Greg is a rhino. It is almost certain that if 'Lily is yellow and Jessica is a mouse' then John dropped the apple. There is a better than even chance that if 'Jessica is a mouse' or 'Lily is yellow' or both then Brian is gray. Chances are slight that if 'Lily is yellow and Jessica is a mouse' then Mary moved to the garden.
It is probable that either 'Greg is a rhino' or 'Brian is gray' but not both.
It is probable that either 'Greg is a rhino' or 'Brian is gray' but not both.
We doubt that either 'Greg is a rhino' or 'Brian is gray' 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.
  0.02::factB.
  0.7::factC.
  %hop1
  0.95::factX:-and(factA,factB).
  0.6::factY:-or(factB,factA).
  0.1::factZ:-and(factA,factB).

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

  query(conclusion).
  
Either 'Greg is a rhino' or 'Brian is gray' but not both.