Co-existing data base management systems (CODASYL DBTG and System R approaches)

The paper addresses the problem of communication between co-existing DBMSs. Specifically, two data models--that is, the Network and Relationals models--have been analyzed using their respective implementations CODASYL DBTG and System R. Feasibility of communication is discussed and mapping mechanisms are suggested between the two DBMSs at the following levels: - Data Model - Data Definition Language - Data Manipulation Language - Access method Restrictions arising from the individual data models in the mapping process have been outlined, in particular the levels at which communication takes place between the two systems: from Network to Relational at the query language level and the converse at the access method level