context: It is likely that Brian is white. It is almost certain that Greg is yellow. We doubt that Emily is a sheep. There is little chance that if 'Emily is a sheep and Brian is white' then Bernhard is a swan. It is highly unlikely that if 'Brian is white' or 'Greg is yellow' or both then John went to the garden. It is probable that if 'Emily is a sheep' or 'Brian is white' or both then Mary left the milk.
hypothesis: It is certain that 'Mary left the milk and Bernhard is a swan'.
valid_hypothesis: It is impossible that 'Mary left the milk and Bernhard is a swan'.
invalid_hypothesis: It is certain that 'Mary left the milk and Bernhard is a swan'.
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.
    0.95::factB.
    0.2::factC.
    %hop1
    0.1::factX:-and(factC,factA).
    0.05::factY:-or(factA,factB).
    0.7::factZ:-or(factC,factA).
  
    %hop2
    conclusion:-and(factZ,factX).
  
    query(conclusion).
    
hypothesis_assertion: 'Mary left the milk and Bernhard is a swan'.