context: It is likely that Brian is a rhino. There is little chance that Julius is green. We doubt that John went to the hallway. It is certain that if either 'Brian is a rhino' or 'Julius is green' but not both then Sandra took the milk. There is almost no chance that if 'Julius is green and Brian is a rhino' then Greg is a frog. Chances are slight that if 'Julius is green' or 'Brian is a rhino' or both then Mary left the football.
hypothesis: It is probably the case that either 'Greg is a frog' or 'Sandra took the milk' but not both.
valid_hypothesis: It is probably the case that either 'Greg is a frog' or 'Sandra took the milk' but not both.
invalid_hypothesis: There is little chance that either 'Greg is a frog' or 'Sandra took the milk' 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
    0.7::factA.
    0.1::factB.
    0.2::factC.
    %hop1
    1.0::factX:-xor(factA,factB).
    0.02::factY:-and(factB,factA).
    0.1::factZ:-or(factB,factA).
  
    %hop2
    conclusion:-xor(factY,factX).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Greg is a frog' or 'Sandra took the milk' but not both.