context: There is almost no chance that Lily is a rhino. We doubt that Bernhard is gray. We doubt that Greg is white. There is a very good chance that if either 'Bernhard is gray' or 'Lily is a rhino' but not both then Jessica is a mouse. We believe that if 'Bernhard is gray and Lily is a rhino' then Fred went to the office. It is highly unlikely that if 'Greg is white' or 'Bernhard is gray' or both then Mary dropped the apple.
hypothesis: We believe that 'Bernhard is gray and Greg is white'.
valid_hypothesis: It is highly unlikely that 'Bernhard is gray and Greg is white'.
invalid_hypothesis: We believe that 'Bernhard is gray and Greg is white'.
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
    0.02::factA.
    0.2::factB.
    0.2::factC.
    %hop1
    0.8::factX:-xor(factB,factA).
    0.75::factY:-and(factB,factA).
    0.05::factZ:-or(factC,factB).
  
    %hop2
    conclusion:-and(factB,factC).
  
    query(conclusion).
    
hypothesis_assertion: 'Bernhard is gray and Greg is white'.