context: We believe that John went to the office. It is likely that Emily is a mouse. It is highly unlikely that Greg is a lion. It is impossible that if 'Greg is a lion and Emily is a mouse' then Julius is a rhino. It is certain that if 'John went to the office and Emily is a mouse' then Bernhard is green. It is impossible that if 'Greg is a lion' or 'Emily is a mouse' or both then Yann is tired.
hypothesis: We believe that either 'Yann is tired' or 'John went to the office' but not both.
valid_hypothesis: We believe that either 'Yann is tired' or 'John went to the office' but not both.
invalid_hypothesis: Chances are slight that either 'Yann is tired' or 'John went to the office' 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.
    0.7::factB.
    0.05::factC.
    %hop1
    0.0::factX:-and(factC,factB).
    1.0::factY:-and(factA,factB).
    0.0::factZ:-or(factC,factB).
  
    %hop2
    conclusion:-xor(factZ,factA).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Yann is tired' or 'John went to the office' but not both.