Database Modeling & Design Fourth Edition- P4: Database technology has evolved rapidly in the three decades since the rise and eventual dominance of relational database systems. While many specialized database systems (object-oriented, spatial, multimedia, etc.) have found substantial user communities in the science and engineering fields, relational systems remain the dominant database technology for business enterprises. | 2 CHAPTER 1 Introduction In this chapter we review the basic concepts of database management and introduce the role of data modeling and database design in the database life cycle. Data and Database Management The basic component of a file in a file system is a data item which is the smallest named unit of data that has meaning in the real world for example last name first name street address ID number or political party. A group of related data items treated as a single unit by an application is called a record. Examples of types of records are order salesperson customer product and department. A file is a collection of records of a single type. Database systems have built upon and expanded these definitions In a relational database a data item is called a column or attribute a record is called a row or tuple and a file is called a table. A database is a more complex object it is a collection of interrelated stored data that serves the needs of multiple users within one or more organizations that is interrelated collections of many different types of tables. The motivations for using databases rather than files include greater availability to a diverse set of users integration of data for easier access to and updating of complex transactions and less redundancy of data. A database management system DBMS is a generalized software system for manipulating databases. A DBMS supports a logical view schema subschema physical view access methods data clustering data definition language data manipulation language and important utilities such as transaction management and concurrency control data integrity crash recovery and security. Relational database systems the dominant type of systems for well-formatted business databases also provide a greater degree of data independence than the earlier hierarchical and network CODASYL database management systems. Data independence is the ability to make changes in either the logical or physical structure of the database .
