Ordering in sequence spaces
A mathematical theory of ordering (with constraints) in sequence spaces was first presented in [7] and [1]. In their setup, an algorithm is sought which “orders” any sequence of length n, i.e., which transforms the sequence x⃗ into the sequence y⃗ (of the same length and with the same symbols in it), such that the number of possible resulting sequences y⃗ is as small as possible. In this sense ordering is a generalization of sorting x⃗ , as this would yield the absolute minimal number of sequences y⃗ .
Ordering in Sequence Spaces: An Overview
Creating order in sequence spaces with simple machines
Entropy reduction, ordering in sequence spaces, and semigroupss of non-negative matrices see here