context: It is probable that Brian is a rhino. It is unlikely that Sandra got the football. It is probably the case that Bernhard is gray. It is probably the case that if 'Sandra got the football' or 'Brian is a rhino' or both then Greg is a swan. It is improbable that if either 'Bernhard is gray' or 'Brian is a rhino' but not both then Julius is white. It is highly likely that if 'Bernhard is gray and Sandra got the football' then Lily is green.
hypothesis: Chances are about even that 'Greg is a swan and Brian is a rhino'.
valid_hypothesis: Chances are about even that 'Greg is a swan and Brian is a rhino'.
invalid_hypothesis: It is impossible that 'Greg is a swan and Brian is a rhino'.
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
    0.7::factA.
    0.2::factB.
    0.7::factC.
    %hop1
    0.7::factX:-or(factB,factA).
    0.1::factY:-xor(factC,factA).
    0.9::factZ:-and(factC,factB).
  
    %hop2
    conclusion:-and(factX,factA).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is a swan and Brian is a rhino'.