A Steiner triple system of order v, denoted STS (v), is a pair (V, B); V is a u-set of elements and B is a collection of 3-subsets of V called blocks. Each unordered pair of elements is contained in precisely one block. There is a substantial body of research on STS, partially because of their wide applicability in the design of experiments, and in the theory of error-correcting codes. In the d...

We introduce two novel evolutionary formulations of the problem of coloring the nodes of a graph. The rst formulation is based on the relationship that exists between a graph’s chromatic number and its acyclic orientations. It views such orientations as individuals and evolves them with the aid of evolutionary operators that are very heavily based on the structure of the graph and its acyclic o...