 This restriction is vital for the proof of invariance. From this, in principle infinite, class of sentences we can measure the length when represented as a program. We select the ones (there might be more than one) of the form \(\overline{T_i}\) that are shortest. The length \(\mathit{l}(\overline{T_i})\) of such a shortest description is a measure for the information content of y. It is asymptotic in the sense that, when the data set y grows to an infinite length, the information content assigned by the choice of another Turing machine will never vary by more than a constant in the limit. Kolmogorov complexity measures the information content of a data set in terms of the shortest description of the set of instructions that produces the data set on a universal computing device.