A more robust representation of measurement uncertainty in such cases can be fashioned from intervals. An interval ["a","b"] is different from a rectangular or uniform probability distribution over the same range in that the latter suggests that the true value lies inside the right half of the range [("a" + "b")/2, "b"] with probability one half, and within any subinterval of ["a","b"] with probability equal to the width of the subinterval divided by "b" – "a". The interval makes no such claims, except simply that the measurement lies somewhere within the interval. Distributions of such measurement intervals can be summarized as probability boxes and Dempster–Shafer structures over the real numbers, which incorporate both aleatoric and epistemic uncertainties.