It is likely that Greg is gray. There is a very good chance that Lily is a rhino. It is impossible that John got the milk. It is unlikely that if 'John got the milk and Lily is a rhino' then Mary is in the hallway. We doubt that if 'Lily is a rhino and Greg is gray' then Bernhard is a swan. It is probably not the case that if 'Greg is gray and Lily is a rhino' then Jessica is a sheep.
It is highly unlikely that 'Greg is gray' or 'Lily is a rhino' or both.
It is almost certain that 'Greg is gray' or 'Lily is a rhino' or both.
It is highly unlikely that 'Greg is gray' or 'Lily is a rhino' 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
  0.7::factA.
  0.8::factB.
  0.0::factC.
  %hop1
  0.2::factX:-and(factC,factB).
  0.2::factY:-and(factB,factA).
  0.25::factZ:-and(factA,factB).

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

  query(conclusion).
  
'Greg is gray' or 'Lily is a rhino' or both.