It is certain that Greg is a swan. There is a better than even chance that Yann is tired. There is a better than even chance that Daniel dropped the apple. It is probably not the case that if 'Daniel dropped the apple' or 'Greg is a swan' or both then Julius is gray. It is improbable that if 'Yann is tired' or 'Daniel dropped the apple' or both then Brian is green. It is likely that if 'Daniel dropped the apple and Greg is a swan' then Gertrude is a cat.
There is a better than even chance that 'Gertrude is a cat' or 'Daniel dropped the apple' or both.
There is a better than even chance that 'Gertrude is a cat' or 'Daniel dropped the apple' or both.
It is highly unlikely that 'Gertrude is a cat' or 'Daniel dropped the apple' 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
  1.0::factA.
  0.6::factB.
  0.6::factC.
  %hop1
  0.25::factX:-or(factC,factA).
  0.1::factY:-or(factB,factC).
  0.7::factZ:-and(factC,factA).

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

  query(conclusion).
  
'Gertrude is a cat' or 'Daniel dropped the apple' or both.