Although the report was not formally adopted by the American National Standards Institute (ANSI), a number of systems were subsequently developed following the DBTG proposal. These systems are now known as CODASYL or DBTG systems. The CODASYL and hierarchical approaches represented the first-generation of DBMSs. We look more closely at these systems on the Web site for this book (see Preface for the URL). However, these two models have some fundamental disadvantages: