We believe that Daniel dropped the apple. It is certain that Greg is a swan. Chances are about even that Jason is tired. There is a very good chance that if either 'Daniel dropped the apple' or 'Greg is a swan' but not both then Julius is white. It is almost certain that if 'Jason is tired and Daniel dropped the apple' then Jessica is a mouse. It is certain that if 'Greg is a swan and Daniel dropped the apple' then Brian is a rhino.
We believe that 'Greg is a swan and Daniel dropped the apple'.
We believe that 'Greg is a swan and Daniel dropped the apple'.
It is probably not the case that 'Greg is a swan and Daniel dropped the apple'.

  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
  0.75::factA.
  1.0::factB.
  0.5::factC.
  %hop1
  0.8::factX:-xor(factA,factB).
  0.95::factY:-and(factC,factA).
  1.0::factZ:-and(factB,factA).

  %hop2
  conclusion:-and(factB,factA).

  query(conclusion).
  
'Greg is a swan and Daniel dropped the apple'.