context: It is highly unlikely that Sandra left the football. We believe that Greg is gray. It is likely that Brian is a rhino. It is probably not the case that if either 'Brian is a rhino' or 'Sandra left the football' but not both then Lily is a frog. Chances are slight that if either 'Greg is gray' or 'Brian is a rhino' but not both then Gertrude is a cat. There is almost no chance that if either 'Greg is gray' or 'Sandra left the football' but not both then Mary discarded the milk.
hypothesis: It is unlikely that either 'Brian is a rhino' or 'Gertrude is a cat' but not both.
valid_hypothesis: It is likely that either 'Brian is a rhino' or 'Gertrude is a cat' but not both.
invalid_hypothesis: It is unlikely that either 'Brian is a rhino' or 'Gertrude is a cat' 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
    0.05::factA.
    0.75::factB.
    0.7::factC.
    %hop1
    0.25::factX:-xor(factC,factA).
    0.1::factY:-xor(factB,factC).
    0.02::factZ:-xor(factB,factA).
  
    %hop2
    conclusion:-xor(factC,factY).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Brian is a rhino' or 'Gertrude is a cat' but not both.