context: It is almost certain that Brian is yellow. Chances are about even that Greg is a rhino. Chances are slight that Lily is a lion. It is likely that if either 'Brian is yellow' or 'Greg is a rhino' but not both then Bernhard is green. It is probably not the case that if 'Lily is a lion and Greg is a rhino' then Julius is a frog. There is little chance that if 'Lily is a lion' or 'Brian is yellow' or both then Mary dropped the apple.
hypothesis: Chances are about even that 'Greg is a rhino' or 'Mary dropped the apple' or both.
valid_hypothesis: Chances are about even that 'Greg is a rhino' or 'Mary dropped the apple' or both.
invalid_hypothesis: It is certain that 'Greg is a rhino' or 'Mary dropped the apple' 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
    0.95::factA.
    0.5::factB.
    0.1::factC.
    %hop1
    0.7::factX:-xor(factA,factB).
    0.25::factY:-and(factC,factB).
    0.1::factZ:-or(factC,factA).
  
    %hop2
    conclusion:-or(factB,factZ).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is a rhino' or 'Mary dropped the apple' or both.