context: There is a very good chance that Gertrude is a sheep. It is likely that Lily is a lion. Chances are slight that Bernhard is green. Chances are slight that if 'Bernhard is green' or 'Gertrude is a sheep' or both then John dropped the apple. There is almost no chance that if either 'Gertrude is a sheep' or 'Lily is a lion' but not both then Greg is a rhino. It is highly likely that if either 'Lily is a lion' or 'Bernhard is green' but not both then Brian is a lion.
hypothesis: There is almost no chance that 'Gertrude is a sheep' or 'Brian is a lion' or both.
valid_hypothesis: It is highly likely that 'Gertrude is a sheep' or 'Brian is a lion' or both.
invalid_hypothesis: There is almost no chance that 'Gertrude is a sheep' or 'Brian is a lion' 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.
    0.7::factB.
    0.1::factC.
    %hop1
    0.1::factX:-or(factC,factA).
    0.02::factY:-xor(factA,factB).
    0.9::factZ:-xor(factB,factC).
  
    %hop2
    conclusion:-or(factA,factZ).
  
    query(conclusion).
    
hypothesis_assertion: 'Gertrude is a sheep' or 'Brian is a lion' or both.