 In Euclid’s example we have two sorts, \(l\) (lines) and \(p\) (points) and a 3-place predicate \(\Join\) with \(\Rank(\Join)=\langle l,p,p,0\rangle\). In the example of binary relations we have two sorts, \(i\) (individuals) and \(r\) (binary relations) and a 3-place predicate symbol \(\epsilon _{2}\) with \(\Rank(\epsilon_{2})=\langle i,i,r,0\rangle\). For the comprehension example we have two sorts, \(i\) (individuals) and \(\pi\) (properties) and a 2-place predicate symbol \(\epsilon_{1}\) with \(\Rank(\epsilon_{1})=\langle i,\pi ,0\rangle\).