 A many-sorted Σ-structure \(\mathcal{A}\) has several universes (or domains) of objects in a family of non-empty sets \(\mathbf{A}_{i}\) (for each \(i\in Sort\)). Structure \(\mathcal{A}\) contains as well: an m-ary relation \(R^{\mathcal{A}}\) for each relation symbol \(R\), an n-ary function \(f^{\mathcal{A}}\) for every n-ary function symbol \(f\) and a distinguish element \(c^{\mathcal{A}}\in \mathbf{A}_{i}\) for every individual constant \(c\). These relations and functions have to be established between elements of the family of domains taking into account their values under function  \(\Rank\).[4]