context: It is probably the case that Greg is white. It is impossible that Jason is tired. Chances are slight that Bernhard is a frog. It is probable that if either 'Jason is tired' or 'Greg is white' but not both then Lily is green. We believe that if 'Jason is tired and Greg is white' then Sandra left the apple. It is probable that if 'Greg is white and Jason is tired' then Mary went to the garden.
hypothesis: It is unlikely that either 'Greg is white' or 'Lily is green' but not both.
valid_hypothesis: It is unlikely that either 'Greg is white' or 'Lily is green' but not both.
invalid_hypothesis: It is probably the case that either 'Greg is white' or 'Lily is green' 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.
    0.0::factB.
    0.1::factC.
    %hop1
    0.7::factX:-xor(factB,factA).
    0.75::factY:-and(factB,factA).
    0.7::factZ:-and(factA,factB).
  
    %hop2
    conclusion:-xor(factA,factX).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Greg is white' or 'Lily is green' but not both.