context: Chances are about even that Greg is a swan. It is probably not the case that John went to the hallway. We doubt that Emily is a cat. Chances are about even that if 'Emily is a cat' or 'John went to the hallway' or both then Julius is a lion. It is probably not the case that if 'Greg is a swan' or 'Emily is a cat' or both then Sandra took the milk. It is highly unlikely that if 'John went to the hallway and Emily is a cat' then Lily is green.
hypothesis: Chances are about even that 'Sandra took the milk' or 'Greg is a swan' or both.
valid_hypothesis: Chances are about even that 'Sandra took the milk' or 'Greg is a swan' or both.
invalid_hypothesis: It is impossible that 'Sandra took the milk' or 'Greg is a swan' 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
    0.5::factA.
    0.25::factB.
    0.2::factC.
    %hop1
    0.5::factX:-or(factC,factB).
    0.25::factY:-or(factA,factC).
    0.05::factZ:-and(factB,factC).
  
    %hop2
    conclusion:-or(factY,factA).
  
    query(conclusion).
    
hypothesis_assertion: 'Sandra took the milk' or 'Greg is a swan' or both.