context: It is unlikely that Mary went to the office. There is a better than even chance that Greg is gray. It is likely that Emily is a sheep. Chances are slight that if 'Emily is a sheep' or 'Mary went to the office' or both then Lily is a swan. It is almost certain that if 'Mary went to the office' or 'Greg is gray' or both then Bernhard is a frog. It is unlikely that if 'Mary went to the office and Greg is gray' then Brian is white.
hypothesis: We doubt that 'Mary went to the office' or 'Brian is white' or both.
valid_hypothesis: We doubt that 'Mary went to the office' or 'Brian is white' or both.
invalid_hypothesis: We believe that 'Mary went to the office' or 'Brian is white' 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
    0.2::factA.
    0.6::factB.
    0.7::factC.
    %hop1
    0.1::factX:-or(factC,factA).
    0.95::factY:-or(factA,factB).
    0.2::factZ:-and(factA,factB).
  
    %hop2
    conclusion:-or(factA,factZ).
  
    query(conclusion).
    
hypothesis_assertion: 'Mary went to the office' or 'Brian is white' or both.