Chances are slight that Lily is a rhino. Chances are slight that John dropped the apple. It is impossible that Daniel put down the milk. It is impossible that if 'John dropped the apple and Lily is a rhino' then Greg is gray. It is likely that if 'Daniel put down the milk and Lily is a rhino' then Mary went to the office. There is a better than even chance that if 'Daniel put down the milk' or 'Lily is a rhino' or both then Bernhard is a frog.
It is highly unlikely that 'Greg is gray' or 'Bernhard is a frog' or both.
It is highly unlikely that 'Greg is gray' or 'Bernhard is a frog' or both.
There is a very good chance that 'Greg is gray' or 'Bernhard is a frog' 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
  0.1::factA.
  0.1::factB.
  0.0::factC.
  %hop1
  0.0::factX:-and(factB,factA).
  0.7::factY:-and(factC,factA).
  0.6::factZ:-or(factC,factA).

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

  query(conclusion).
  
'Greg is gray' or 'Bernhard is a frog' or both.