There is a very good chance that John dropped the apple. We believe that Brian is a swan. It is certain that Emily is a wolf. It is highly likely that if 'John dropped the apple and Brian is a swan' then Lily is gray. It is highly likely that if either 'Brian is a swan' or 'John dropped the apple' but not both then Mary went to the bedroom. Chances are about even that if either 'Brian is a swan' or 'Emily is a wolf' but not both then Julius is green.
We doubt that 'Emily is a wolf' or 'Julius is green' or both.
It is certain that 'Emily is a wolf' or 'Julius is green' or both.
We doubt that 'Emily is a wolf' or 'Julius is green' 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.
  0.75::factB.
  1.0::factC.
  %hop1
  0.9::factX:-and(factA,factB).
  0.9::factY:-xor(factB,factA).
  0.5::factZ:-xor(factB,factC).

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

  query(conclusion).
  
'Emily is a wolf' or 'Julius is green' or both.