Chances are about even that Jason is thirsty. Chances are slight that Sandra put down the milk. It is unlikely that Brian is a swan. It is probable that if 'Brian is a swan and Jason is thirsty' then Julius is a frog. It is likely that if 'Brian is a swan and Sandra put down the milk' then Mary went to the office. It is probable that if either 'Brian is a swan' or 'Jason is thirsty' but not both then Daniel dropped the apple.
There is a better than even chance that 'Daniel dropped the apple' or 'Jason is thirsty' or both.
There is a better than even chance that 'Daniel dropped the apple' or 'Jason is thirsty' or both.
It is impossible that 'Daniel dropped the apple' or 'Jason is thirsty' 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.
  0.1::factB.
  0.2::factC.
  %hop1
  0.7::factX:-and(factC,factA).
  0.7::factY:-and(factC,factB).
  0.7::factZ:-xor(factC,factA).

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

  query(conclusion).
  
'Daniel dropped the apple' or 'Jason is thirsty' or both.