context: Chances are about even that Yann is tired. It is unlikely that Greg is green. We doubt that Lily is a rhino. There is a very good chance that if either 'Greg is green' or 'Yann is tired' but not both then Bernhard is a swan. It is almost certain that if either 'Greg is green' or 'Lily is a rhino' but not both then Mary grabbed the milk. There is little chance that if 'Yann is tired' or 'Greg is green' or both then Brian is yellow.
hypothesis: It is certain that 'Brian is yellow' or 'Yann is tired' or both.
valid_hypothesis: Chances are about even that 'Brian is yellow' or 'Yann is tired' or both.
invalid_hypothesis: It is certain that 'Brian is yellow' or 'Yann is tired' 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
    0.5::factA.
    0.2::factB.
    0.2::factC.
    %hop1
    0.8::factX:-xor(factB,factA).
    0.95::factY:-xor(factB,factC).
    0.1::factZ:-or(factA,factB).
  
    %hop2
    conclusion:-or(factZ,factA).
  
    query(conclusion).
    
hypothesis_assertion: 'Brian is yellow' or 'Yann is tired' or both.