context: Chances are about even that John left the football. Chances are about even that Brian is a swan. There is almost no chance that Julius is yellow. It is probably not the case that if 'Julius is yellow' or 'Brian is a swan' or both then Emily is a wolf. It is highly likely that if either 'Brian is a swan' or 'John left the football' but not both then Bill went to the kitchen. It is highly likely that if either 'John left the football' or 'Julius is yellow' but not both then Mary moved to the garden.
hypothesis: Chances are about even that 'John left the football' or 'Julius is yellow' or both.
valid_hypothesis: Chances are about even that 'John left the football' or 'Julius is yellow' or both.
invalid_hypothesis: It is impossible that 'John left the football' or 'Julius is yellow' 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.
    0.5::factB.
    0.02::factC.
    %hop1
    0.25::factX:-or(factC,factB).
    0.9::factY:-xor(factB,factA).
    0.9::factZ:-xor(factA,factC).
  
    %hop2
    conclusion:-or(factA,factC).
  
    query(conclusion).
    
hypothesis_assertion: 'John left the football' or 'Julius is yellow' or both.