##### Wikipedia

**ISBL**

**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.

**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.