This book is in three parts. The first part describes the database management system as it should be and discusses the various facilities it should offer the database administra- tor, the programmer and the general user. The second part describes SQL, including the schema and sub-schema defini- tion languages, the module language, the module language and themanipulation language while a third part is devoted to NDL including the commands to create the schema and the views, the module and the data manipulation language.