context: It is impossible that Jessica is a mouse. It is almost certain that John went to the office. We doubt that Julius is white. It is unlikely that if either 'Jessica is a mouse' or 'Julius is white' but not both then Gertrude is a cat. There is a better than even chance that if 'Julius is white and John went to the office' then Greg is a rhino. Chances are slight that if either 'Julius is white' or 'John went to the office' but not both then Mary left the football.
hypothesis: It is unlikely that 'Gertrude is a cat' or 'John went to the office' or both.
valid_hypothesis: It is almost certain that 'Gertrude is a cat' or 'John went to the office' or both.
invalid_hypothesis: It is unlikely that 'Gertrude is a cat' or 'John went to the office' 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
    0.0::factA.
    0.95::factB.
    0.2::factC.
    %hop1
    0.2::factX:-xor(factA,factC).
    0.6::factY:-and(factC,factB).
    0.1::factZ:-xor(factC,factB).
  
    %hop2
    conclusion:-or(factX,factB).
  
    query(conclusion).
    
hypothesis_assertion: 'Gertrude is a cat' or 'John went to the office' or both.