. "829"^^ . . . "848209434"^^ . "3946520"^^ . . . . . . . . . "ISBL"@en . . . . "ISBL (Information Systems Base Language) is the relational algebra notation that was invented for PRTV, one of the earliest database management systems to implement E.F. Codd's relational model of data."@en . . . "ISBL (Information Systems Base Language) is the relational algebra notation that was invented for PRTV, one of the earliest database management systems to implement E.F. Codd's relational model of data."@en . . . . . . . . . . .