context: It is probably the case that Brian is a rhino. We believe that Emily is a mouse. It is unlikely that Bernhard is a frog. It is improbable that if 'Bernhard is a frog' or 'Brian is a rhino' or both then Mary left the football. It is likely that if 'Brian is a rhino and Bernhard is a frog' then Greg is white. There is a better than even chance that if 'Emily is a mouse and Brian is a rhino' then Lily is yellow.
hypothesis: It is highly likely that either 'Greg is white' or 'Mary left the football' but not both.
valid_hypothesis: It is unlikely that either 'Greg is white' or 'Mary left the football' but not both.
invalid_hypothesis: It is highly likely that either 'Greg is white' or 'Mary left the football' 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.
    0.75::factB.
    0.2::factC.
    %hop1
    0.1::factX:-or(factC,factA).
    0.7::factY:-and(factA,factC).
    0.6::factZ:-and(factB,factA).
  
    %hop2
    conclusion:-xor(factY,factX).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Greg is white' or 'Mary left the football' but not both.