All unquantified variables in this entry should be taken as tacitly universally quantified; hence all axioms should be taken as universal closures. No axiom requires more than three quantified variables; hence a translation of first-order theories into relation algebra is possible.
This entry emphasizes the assumption of universal quantification for unspecified variables and the requirement that all axioms be universal closures. It also highlights the possibility of translating first-order theories into relational algebra due to the limited number of quantifiers required by each axiom.