Abstract
The relational complexity, introduced by G. Cherlin, G.
Martin, and D. Saracino, is a measure of ultrahomogeneity of a relational structure.
It provides an information on minimal arity of additional invariant relations needed to turn given structure into an ultrahomogeneous one. The original motivation was group theory.
This work focuses more on structures and provides an alternative approach. Our study is motivated by related concept of lift complexity studied by Hubi. cka and Nesetril. (C) 2015 Mathematical Institute Slovak Academy of Sciences