context: It is highly unlikely that Greg is a rhino. Chances are about even that Bernhard is yellow. There is little chance that Mary got the football. It is highly unlikely that if either 'Mary got the football' or 'Greg is a rhino' but not both then Jason is tired. It is likely that if 'Mary got the football' or 'Bernhard is yellow' or both then Sandra dropped the milk. It is probable that if 'Mary got the football' or 'Bernhard is yellow' or both then Julius is a frog.
hypothesis: It is highly unlikely that 'Sandra dropped the milk and Mary got the football'.
valid_hypothesis: It is highly unlikely that 'Sandra dropped the milk and Mary got the football'.
invalid_hypothesis: We believe that 'Sandra dropped the milk 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
    0.05::factA.
    0.5::factB.
    0.1::factC.
    %hop1
    0.05::factX:-xor(factC,factA).
    0.7::factY:-or(factC,factB).
    0.7::factZ:-or(factC,factB).
  
    %hop2
    conclusion:-and(factY,factC).
  
    query(conclusion).
    
hypothesis_assertion: 'Sandra dropped the milk and Mary got the football'.