  We propose a Relational Calculus based on the concept of unary relation. In
this Relational Calculus different axiomatic systems converge to a model called
Dynamic Generative System with Symmetry (DGSS). In DGSS we define the concepts
of relational set and function and prove that extensionality and the
substitution property of equality are theorems of DGSS. As a first
exemplification of DGSS, we construct a model of natural numbers without
relying on Peano's Axioms. Eventually, some new clarifications regarding the
nature of the number zero are given.
