context: There is little chance that John put down the milk. It is unlikely that Sandra grabbed the apple. Chances are slight that Julius is gray. There is a better than even chance that if 'Sandra grabbed the apple and John put down the milk' then Emily is a mouse. There is little chance that if 'John put down the milk' or 'Sandra grabbed the apple' or both then Greg is a swan. It is likely that if 'John put down the milk and Julius is gray' then Mary got the football.
hypothesis: It is impossible that 'Greg is a swan and Mary got the football'.
valid_hypothesis: It is impossible that 'Greg is a swan and Mary got the football'.
invalid_hypothesis: It is certain that 'Greg is a swan and Mary got the football'.
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.
    0.2::factB.
    0.1::factC.
    %hop1
    0.6::factX:-and(factB,factA).
    0.1::factY:-or(factA,factB).
    0.7::factZ:-and(factA,factC).
  
    %hop2
    conclusion:-and(factY,factZ).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is a swan and Mary got the football'.