context: There is little chance that Brian is a swan. It is impossible that Julius is a swan. It is probably not the case that Gertrude is a mouse. There is a better than even chance that if either 'Brian is a swan' or 'Gertrude is a mouse' but not both then Bernhard is yellow. It is impossible that if either 'Gertrude is a mouse' or 'Julius is a swan' but not both then Mary took the football. It is likely that if either 'Brian is a swan' or 'Gertrude is a mouse' but not both then Greg is a frog.
hypothesis: It is impossible that 'Mary took the football and Bernhard is yellow'.
valid_hypothesis: It is impossible that 'Mary took the football and Bernhard is yellow'.
invalid_hypothesis: There is a very good chance that 'Mary took the football and Bernhard is yellow'.
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.
    0.0::factB.
    0.25::factC.
    %hop1
    0.6::factX:-xor(factA,factC).
    0.0::factY:-xor(factC,factB).
    0.7::factZ:-xor(factA,factC).
  
    %hop2
    conclusion:-and(factY,factX).
  
    query(conclusion).
    
hypothesis_assertion: 'Mary took the football and Bernhard is yellow'.