context: There is a very good chance that Brian is a swan. It is unlikely that John took the football. There is little chance that Sandra got the milk. It is probable that if either 'Brian is a swan' or 'Sandra got the milk' but not both then Yann is hungry. There is a very good chance that if either 'Sandra got the milk' or 'John took the football' but not both then Greg is a rhino. It is almost certain that if either 'John took the football' or 'Brian is a swan' but not both then Julius is green.
hypothesis: Chances are slight that 'Yann is hungry' or 'Greg is a rhino' or both.
valid_hypothesis: There is a better than even chance that 'Yann is hungry' or 'Greg is a rhino' or both.
invalid_hypothesis: Chances are slight that 'Yann is hungry' or 'Greg is a rhino' or both.
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
    0.8::factA.
    0.2::factB.
    0.1::factC.
    %hop1
    0.7::factX:-xor(factA,factC).
    0.8::factY:-xor(factC,factB).
    0.95::factZ:-xor(factB,factA).
  
    %hop2
    conclusion:-or(factX,factY).
  
    query(conclusion).
    
hypothesis_assertion: 'Yann is hungry' or 'Greg is a rhino' or both.