context: Chances are about even that Brian is a swan. We believe that John went to the garden. Chances are about even that Greg is green. It is improbable that if either 'Greg is green' or 'Brian is a swan' but not both then Gertrude is a mouse. It is likely that if 'Brian is a swan' or 'John went to the garden' or both then Mary dropped the milk. It is improbable that if 'Greg is green' or 'Brian is a swan' or both then Julius is a rhino.
hypothesis: Chances are about even that 'Julius is a rhino and Gertrude is a mouse'.
valid_hypothesis: It is impossible that 'Julius is a rhino and Gertrude is a mouse'.
invalid_hypothesis: Chances are about even that 'Julius is a rhino and Gertrude is a mouse'.
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
    0.5::factA.
    0.75::factB.
    0.5::factC.
    %hop1
    0.1::factX:-xor(factC,factA).
    0.7::factY:-or(factA,factB).
    0.1::factZ:-or(factC,factA).
  
    %hop2
    conclusion:-and(factZ,factX).
  
    query(conclusion).
    
hypothesis_assertion: 'Julius is a rhino and Gertrude is a mouse'.