context: It is certain that Jessica is a cat. It is unlikely that Brian is white. Chances are about even that Greg is a rhino. Chances are slight that if 'Brian is white and Greg is a rhino' then Julius is a swan. It is probably the case that if either 'Greg is a rhino' or 'Jessica is a cat' but not both then Mary got the milk. There is little chance that if 'Jessica is a cat' or 'Greg is a rhino' or both then John discarded the apple.
hypothesis: It is highly likely that either 'John discarded the apple' or 'Brian is white' but not both.
valid_hypothesis: It is probably not the case that either 'John discarded the apple' or 'Brian is white' but not both.
invalid_hypothesis: It is highly likely that either 'John discarded the apple' or 'Brian is white' but not 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
    1.0::factA.
    0.2::factB.
    0.5::factC.
    %hop1
    0.1::factX:-and(factB,factC).
    0.7::factY:-xor(factC,factA).
    0.1::factZ:-or(factA,factC).
  
    %hop2
    conclusion:-xor(factZ,factB).
  
    query(conclusion).
    
hypothesis_assertion: Either 'John discarded the apple' or 'Brian is white' but not both.