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.

Other articles related to "isbl":

Relational Algebra - Implementations
... The first query language to be based on Codd's algebra was ISBL, and this pioneering work has been acclaimed by many authorities as having shown the way to make ... relational DBMS that followed the ISBL example ... for use in teaching relational database theory, and its query language also draws on ISBL's ideas ...