context: Chances are about even that John moved to the office. There is little chance that Gertrude is a mouse. It is highly unlikely that Mary is in the school. It is certain that if 'Mary is in the school and Gertrude is a mouse' then Julius is yellow. It is highly likely that if either 'John moved to the office' or 'Mary is in the school' but not both then Greg is a lion. It is improbable that if 'John moved to the office' or 'Gertrude is a mouse' or both then Brian is a swan.
hypothesis: There is little chance that either 'Mary is in the school' or 'Gertrude is a mouse' but not both.
valid_hypothesis: There is little chance that either 'Mary is in the school' or 'Gertrude is a mouse' but not both.
invalid_hypothesis: It is highly likely that either 'Mary is in the school' or 'Gertrude is a mouse' 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
    0.5::factA.
    0.1::factB.
    0.05::factC.
    %hop1
    1.0::factX:-and(factC,factB).
    0.9::factY:-xor(factA,factC).
    0.1::factZ:-or(factA,factB).
  
    %hop2
    conclusion:-xor(factC,factB).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Mary is in the school' or 'Gertrude is a mouse' but not both.