Catalan structures and Catalan pairs

A Catalan pair is a pair of binary relations (S,R) satisfying some axioms. These pairs are enumerated by the well-known Catalan numbers, and have been introduced with the aim of giving a common language to many structures counted by Catalan numbers. Here, a simple method is given to pass from the recursive definition of a generic Catalan structure to the recursive definition of the Catalan pair on the same structure, thus giving an automatic way of interpreting Catalan structures in terms of Catalan pairs. The method is applied to several well-known Catalan structures, focusing on the combinatorial meaning of the relations S and R in each case considered.