context: There is a better than even chance that Bernhard is a frog. It is certain that John discarded the apple. It is highly likely that Mary put down the milk. There is a better than even chance that if 'Bernhard is a frog and Mary put down the milk' then Jeff left the apple. There is a very good chance that if 'Mary put down the milk' or 'John discarded the apple' or both then Julius is a swan. It is probably not the case that if either 'John discarded the apple' or 'Mary put down the milk' but not both then Brian is a lion.
hypothesis: It is highly unlikely that 'John discarded the apple' or 'Bernhard is a frog' or both.
valid_hypothesis: It is certain that 'John discarded the apple' or 'Bernhard is a frog' or both.
invalid_hypothesis: It is highly unlikely that 'John discarded the apple' 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
    0.6::factA.
    1.0::factB.
    0.9::factC.
    %hop1
    0.6::factX:-and(factA,factC).
    0.8::factY:-or(factC,factB).
    0.25::factZ:-xor(factB,factC).
  
    %hop2
    conclusion:-or(factB,factA).
  
    query(conclusion).
    
hypothesis_assertion: 'John discarded the apple' or 'Bernhard is a frog' or both.