context: It is highly unlikely that Lily is a swan. Chances are slight that John left the football. It is impossible that Sandra dropped the milk. Chances are about even that if 'Sandra dropped the milk and Lily is a swan' then Mary got the football. It is unlikely that if 'Lily is a swan and John left the football' then Fred went to the garden. It is probably the case that if either 'Lily is a swan' or 'John left the football' but not both then Brian is a rhino.
hypothesis: There is a very good chance that 'Fred went to the garden and John left the football'.
valid_hypothesis: It is impossible that 'Fred went to the garden and John left the football'.
invalid_hypothesis: There is a very good chance that 'Fred went to the garden and John left 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
    0.05::factA.
    0.1::factB.
    0.0::factC.
    %hop1
    0.5::factX:-and(factC,factA).
    0.2::factY:-and(factA,factB).
    0.7::factZ:-xor(factA,factB).
  
    %hop2
    conclusion:-and(factY,factB).
  
    query(conclusion).
    
hypothesis_assertion: 'Fred went to the garden and John left the football'.