context: We believe that Julius is a lion. There is little chance that Sandra dropped the milk. There is a better than even chance that Fred went to the garden. It is certain that if 'Fred went to the garden' or 'Julius is a lion' or both then Bernhard is a swan. Chances are slight that if 'Sandra dropped the milk and Fred went to the garden' then Brian is a rhino. There is little chance that if 'Fred went to the garden' or 'Julius is a lion' or both then John picked up the apple.
hypothesis: There is almost no chance that either 'Fred went to the garden' or 'Brian is a rhino' but not both.
valid_hypothesis: There is a better than even chance that either 'Fred went to the garden' or 'Brian is a rhino' but not both.
invalid_hypothesis: There is almost no chance that either 'Fred went to the garden' or 'Brian is a rhino' 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
    0.75::factA.
    0.1::factB.
    0.6::factC.
    %hop1
    1.0::factX:-or(factC,factA).
    0.1::factY:-and(factB,factC).
    0.1::factZ:-or(factC,factA).
  
    %hop2
    conclusion:-xor(factC,factY).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Fred went to the garden' or 'Brian is a rhino' but not both.