context: It is improbable that Sumit is thirsty. It is unlikely that Mary left the football. It is highly unlikely that Lily is a lion. There is a very good chance that if 'Lily is a lion' or 'Sumit is thirsty' or both then Sandra dropped the milk. Chances are slight that if 'Mary left the football' or 'Lily is a lion' or both then John grabbed the apple. We believe that if 'Sumit is thirsty' or 'Mary left the football' or both then Bernhard is yellow.
hypothesis: There is a very good chance that either 'Mary left the football' or 'Bernhard is yellow' but not both.
valid_hypothesis: It is improbable that either 'Mary left the football' or 'Bernhard is yellow' but not both.
invalid_hypothesis: There is a very good chance that either 'Mary left the football' or 'Bernhard is yellow' 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
    0.1::factA.
    0.2::factB.
    0.05::factC.
    %hop1
    0.8::factX:-or(factC,factA).
    0.1::factY:-or(factB,factC).
    0.75::factZ:-or(factA,factB).
  
    %hop2
    conclusion:-xor(factB,factZ).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Mary left the football' or 'Bernhard is yellow' but not both.