context: There is little chance that Brian is a swan. There is a very good chance that Julius is a rhino. It is almost certain that Bernhard is a frog. It is improbable that if either 'Bernhard is a frog' or 'Brian is a swan' but not both then Fred is in the cinema. It is improbable that if 'Bernhard is a frog and Brian is a swan' then John moved to the office. It is almost certain that if 'Brian is a swan' or 'Bernhard is a frog' or both then Greg is yellow.
hypothesis: It is almost certain that 'Greg is yellow' or 'Bernhard is a frog' or both.
valid_hypothesis: It is almost certain that 'Greg is yellow' or 'Bernhard is a frog' or both.
invalid_hypothesis: It is highly unlikely that 'Greg is yellow' or 'Bernhard is a frog' 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
    0.1::factA.
    0.8::factB.
    0.95::factC.
    %hop1
    0.1::factX:-xor(factC,factA).
    0.1::factY:-and(factC,factA).
    0.95::factZ:-or(factA,factC).
  
    %hop2
    conclusion:-or(factZ,factC).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is yellow' or 'Bernhard is a frog' or both.