title: on the semantics of `` now '' in databases. authors: j clifford , c dyreson , t isakowitz , c jensen , r snodgrass. venue: acm trans . database syst .. year: 1997
title: on the semantics of \ \ now. authors: j cliord , c dyreson , t isakowitz , cs jensen , rt. venue: databases . acm transactions on database systems ,. year: nan