Database Systems Chapter 1 The Worlds of Database Systems

Section 1.1 Evolution of Database Systems The DBMS is expected to : 1. Allow users to create new databases and specify their schemas ( logical structure of the data ), using a specialized data - definition language. 2. Give users the ability to query the data ( a “query" is a question about the data ) and modify the data, using an appropriate language, often called a query language or data - manipulation language. 3. Support the storage of very large amounts of data - many terabytes or more - over a long period of time, allowing efficient access to the data for queries and database modifications.

Evolution of Database Systems The DBMS is also expected to: 4. Enable durability, the recovery of the database in the face of failures, errors of many kinds, or intentional misuse. 5. Control access to data from many users at once, without allowing unexpected interactions among users ( called isolation ) and without actions on the data to be performed partially but not completely ( called atomicity )

Some History Early Database Management Systems Adabas Relational Database Systems – 1970 E. F. Codd - Date Smaller and Smaller Systems and XML Large collections of small documents tagged with XML serve as a database Bigger and Bigger Systems Petabytes Information Integration – joining information in many related databases into a whole Data warehouses

Section 1.2 Overview of a Database Management System There is a difference between commands used by users and application programs, and those used by a database administrator Data-Definition Language Commands Defining tables and restrictions on data Overview of Query Processing Answering the Query Transaction Processing Storage and Buffer Management Transaction Processing The ACID Properties of Transactions The Query Processor The query compiler with parser, preprocessor, and optimizer The execution engine

Section 1.3 Outline of Database-System Studies Part I Relational Database Modeling Function dependencies and normalization E/R model, UML, and Object Definition Language (ODL) Part II: Relational Database Programming Relational algebra and SQL Part III: Semi-structured Data Modeling and Programming XML because of the Web Part IV: Database System Implementation Storage management, query processing, transaction processing, logging and recovery Part V: Modern Database System Issues Search engines and data mining