context: We doubt that Sandra took the football. It is unlikely that John discarded the milk. There is little chance that Julius is a rhino. There is almost no chance that if 'Julius is a rhino and John discarded the milk' then Fred went to the garden. It is impossible that if either 'Julius is a rhino' or 'Sandra took the football' but not both then Greg is a lion. It is impossible that if 'Julius is a rhino and John discarded the milk' then Bernhard is a frog.
hypothesis: It is impossible that 'John discarded the milk and Fred went to the garden'.
valid_hypothesis: It is impossible that 'John discarded the milk and Fred went to the garden'.
invalid_hypothesis: It is highly likely that 'John discarded the milk and Fred went to the garden'.
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
    0.2::factA.
    0.2::factB.
    0.1::factC.
    %hop1
    0.02::factX:-and(factC,factB).
    0.0::factY:-xor(factC,factA).
    0.0::factZ:-and(factC,factB).
  
    %hop2
    conclusion:-and(factB,factX).
  
    query(conclusion).
    
hypothesis_assertion: 'John discarded the milk and Fred went to the garden'.