Basic Relational Data Model

Basic concepts of information models, their realisation in databases comprising data objects and object relationships, and their management by DBMS’s that separate structure (schema) from content, were introduced in the last chapter. The need for a DDL to define the structure of entities and their relationships, and for a DML to specify manipulation of database contents were also established. These concepts, however, were presented in quite abstract terms, with no commitment to any particular data structure for entities or links nor to any particular function to manipulate data objects.