context: Chances are slight that Sandra left the milk. We believe that Jeff went to the bedroom. Chances are slight that Brian is a rhino. It is almost certain that if either 'Brian is a rhino' or 'Jeff went to the bedroom' but not both then Bernhard is a swan. Chances are slight that if 'Jeff went to the bedroom and Brian is a rhino' then Julius is white. Chances are about even that if 'Sandra left the milk and Brian is a rhino' then Emily is a sheep.
hypothesis: It is impossible that 'Jeff went to the bedroom' or 'Julius is white' or both.
valid_hypothesis: We believe that 'Jeff went to the bedroom' or 'Julius is white' or both.
invalid_hypothesis: It is impossible that 'Jeff went to the bedroom' or 'Julius is white' or both.
problog: 
    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
    0.1::factA.
    0.75::factB.
    0.1::factC.
    %hop1
    0.95::factX:-xor(factC,factB).
    0.1::factY:-and(factB,factC).
    0.5::factZ:-and(factA,factC).
  
    %hop2
    conclusion:-or(factB,factY).
  
    query(conclusion).
    
hypothesis_assertion: 'Jeff went to the bedroom' or 'Julius is white' or both.