context: We doubt that Mary grabbed the milk. Chances are about even that Jessica is a mouse. It is certain that Greg is a swan. Chances are about even that if 'Mary grabbed the milk' or 'Jessica is a mouse' or both then John put down the apple. There is a very good chance that if 'Mary grabbed the milk' or 'Jessica is a mouse' or both then Julius is a frog. Chances are about even that if either 'Greg is a swan' or 'Jessica is a mouse' but not both then Brian is a rhino.
hypothesis: It is certain that 'Mary grabbed the milk' or 'Greg is a swan' or both.
valid_hypothesis: It is certain that 'Mary grabbed the milk' or 'Greg is a swan' or both.
invalid_hypothesis: There is little chance that 'Mary grabbed 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
    0.2::factA.
    0.5::factB.
    1.0::factC.
    %hop1
    0.5::factX:-or(factA,factB).
    0.8::factY:-or(factA,factB).
    0.5::factZ:-xor(factC,factB).
  
    %hop2
    conclusion:-or(factA,factC).
  
    query(conclusion).
    
hypothesis_assertion: 'Mary grabbed the milk' or 'Greg is a swan' or both.