On the variety question for wRRA (Q2474097)

A relation algebra \(U\) is said to be representable if it is isomorphic to a proper relation algebra (or a set relation algebra); it is said to be weakly representable if it has a representation respecting all the operations except \(+\) and \(-.\) In this paper the author considers a question of \textit{B. Jónsson} [Trans. Am. Math. Soc. 92, 449--464 (1959; Zbl 0105.25302)], whether the class of weakly representable relations algebras is a variety. He proves that the class is closed under taking homomorphic images provided that a certain embedding condition holds.