context: There is a better than even chance that Bernhard is a rhino. Chances are slight that Sumit is bored. It is probably the case that Julius is a lion. It is probably the case that if either 'Bernhard is a rhino' or 'Sumit is bored' but not both then Gertrude is a mouse. It is probable that if either 'Bernhard is a rhino' or 'Sumit is bored' but not both then Greg is a swan. Chances are slight that if 'Sumit is bored and Bernhard is a rhino' then Mary took the football.
hypothesis: We believe that 'Greg is a swan and Julius is a lion'.
valid_hypothesis: It is probably not the case that 'Greg is a swan and Julius is a lion'.
invalid_hypothesis: We believe that 'Greg is a swan and Julius is a lion'.
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
    0.6::factA.
    0.1::factB.
    0.7::factC.
    %hop1
    0.7::factX:-xor(factA,factB).
    0.7::factY:-xor(factA,factB).
    0.1::factZ:-and(factB,factA).
  
    %hop2
    conclusion:-and(factY,factC).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is a swan and Julius is a lion'.