Finiteness Conditions for Algebras of Relations

Algebras of relations on a given set are considered; operations in an algebra are specified by various formulas of first-order logic. Different ways of introducing finiteness conditions for such algebras are studied. For each natural $n$, an example of an algebra is constructed that is generated by one $n$-ary relation and cannot be generated by its relations of smaller arity. An open problem is formulated.