Chances are about even that Fred put down the apple. It is probable that Gertrude is a sheep. There is a better than even chance that Mary is in the hallway. There is little chance that if 'Mary is in the hallway and Gertrude is a sheep' then Lily is gray. There is little chance that if 'Mary is in the hallway' or 'Gertrude is a sheep' or both then Greg is a swan. There is a very good chance that if 'Mary is in the hallway' or 'Gertrude is a sheep' or both then John got the milk.
There is a very good chance that 'Gertrude is a sheep' or 'Fred put down the apple' or both.
There is a very good chance that 'Gertrude is a sheep' or 'Fred put down the apple' or both.
We doubt that 'Gertrude is a sheep' or 'Fred put down the apple' 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.
  0.6::factC.
  %hop1
  0.1::factX:-and(factC,factB).
  0.1::factY:-or(factC,factB).
  0.8::factZ:-or(factC,factB).

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

  query(conclusion).
  
'Gertrude is a sheep' or 'Fred put down the apple' or both.