There is a very good chance that John took the apple. There is a very good chance that Bill went to the garden. It is certain that Greg is a lion. It is highly likely that if either 'Bill went to the garden' or 'John took the apple' but not both then Mary got the milk. There is a very good chance that if 'Bill went to the garden and Greg is a lion' then Lily is gray. There is little chance that if 'Greg is a lion' or 'Bill went to the garden' or both then Bernhard is a rhino.
It is certain that 'Lily is gray' or 'Greg is a lion' or both.
It is certain that 'Lily is gray' or 'Greg is a lion' or both.
It is improbable that 'Lily is gray' or 'Greg is a lion' 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
  0.8::factA.
  0.8::factB.
  1.0::factC.
  %hop1
  0.9::factX:-xor(factB,factA).
  0.8::factY:-and(factB,factC).
  0.1::factZ:-or(factC,factB).

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

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