There is a very good chance that John dropped the apple. It is probably the case that Jessica is a mouse. It is unlikely that Brian is white. Chances are about even that if 'Jessica is a mouse and Brian is white' then Bernhard is a swan. It is probably the case that if 'John dropped the apple and Jessica is a mouse' then Lily is green. Chances are slight that if 'Brian is white and John dropped the apple' then Antoine is thirsty.
We believe that 'Jessica is a mouse' or 'Brian is white' or both.
We believe that 'Jessica is a mouse' or 'Brian is white' or both.
It is impossible that 'Jessica is a mouse' or 'Brian is white' 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.
  0.7::factB.
  0.2::factC.
  %hop1
  0.5::factX:-and(factB,factC).
  0.7::factY:-and(factA,factB).
  0.1::factZ:-and(factC,factA).

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

  query(conclusion).
  
'Jessica is a mouse' or 'Brian is white' or both.