Chances are about even that Greg is a swan. It is probably the case that John put down the apple. It is unlikely that Lily is a lion. There is a better than even chance that if either 'Greg is a swan' or 'Lily is a lion' but not both then Mary dropped the milk. It is unlikely that if either 'Lily is a lion' or 'Greg is a swan' but not both then Jason is tired. It is improbable that if 'John put down the apple and Greg is a swan' then Julius is a frog.
It is probably not the case that 'Jason is tired' or 'Lily is a lion' or both.
It is probably not the case that 'Jason is tired' or 'Lily is a lion' or both.
It is probable that 'Jason is tired' or 'Lily 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
  0.5::factA.
  0.7::factB.
  0.2::factC.
  %hop1
  0.6::factX:-xor(factA,factC).
  0.2::factY:-xor(factC,factA).
  0.1::factZ:-and(factB,factA).

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

  query(conclusion).
  
'Jason is tired' or 'Lily is a lion' or both.