1. —— Introduction to Database Systems Database Systems: A practical Approach to Design, Implementation, and Management (4 rd edition) Thomas Connolly Carolyn Begg Addison-Wesley 2005 Professional English for Software Engineering Shuhua Ruan, School of Software, Sichuan University

2. Topics u Some Common Applications of Database Systems u Database System Architectures u The History of the Development of DBMSs u Two Core Concepts of Database Systems 2 Shuhua Ruan, School of Software, Sichuan University

3. Introduction to Database Systems Database systems are designed to manage large bodies of information, which is a collection of interrelated data relevant to an enterprise. 3 Shuhua Ruan, School of Software, Sichuan University

4. Introduction to Database Systems Management of data involves both defining structures for storage of information and providing mechanisms for the manipulation of information. 4 Shuhua Ruan, School of Software, Sichuan University

5. Introduction to Database Systems Because information is so important in most organizations, database systems must ensure the safety of the information stored, despite system crashes or attempts at unauthorized access. 5 Shuhua Ruan, School of Software, Sichuan University

6. Introduction to Database Systems In addition, if data are to be shared among several users, database systems must avoid possible anomalous results. 6 Shuhua Ruan, School of Software, Sichuan University

7. Some Common Applications of Database Systems Over the last four decades, Databases are widely used and form an essential part of almost all enterprises today. The Internet revolution of the late 1990s sharply increased direct user access to databases. 7 Shuhua Ruan, School of Software, Sichuan University

8. Examples of Database Applications u Banking For customer information, accounts, loans, and banking transactions. When you access a bank Web site and you can retrieve your bank balance and transaction information, the information is retrieved from the bank's database system. 8 Shuhua Ruan, School of Software, Sichuan University

9. Examples of Database Applications u Airlines For reservation and schedule information. Airlines were among the first to use database in a geographically distributed manner -- terminals situated around the world can access the central database system through data networks. 9 Shuhua Ruan, School of Software, Sichuan University

10. Examples of Database Applications u Online Bookstore For product information, such as books, music collections, customer and purchase information. When You browse a book or music collection from Internet, you are accessing data stored in a database. When you enter an order online, your order is stored in the database. 10 Shuhua Ruan, School of Software, Sichuan University

11. Examples of Database Applications u Human Resources For information about employees, salaries, payroll taxes and benefits, and for generation of paychecks. 11 Shuhua Ruan, School of Software, Sichuan University

12. Examples of Database Applications u Electronic Government For information about news, administrative policies and rules for various affairs. When you access a government Web site, online affair systems can provide various services for you and deal with various affairs. 12 Shuhua Ruan, School of Software, Sichuan University

13. Examples of Database Applications u Education For teacher, student and course information, course registrations, and grades. All are stored in a database. 13 Shuhua Ruan, School of Software, Sichuan University

14. A Library Database System u In general, the goal of the library database is to maintain detailed information about: library's members library's holdings books borrowed by a member hold requests sent by a member 14 Shuhua Ruan, School of Software, Sichuan University

15. A Library Database System 15 Shuhua Ruan, School of Software, Sichuan University

16. A Library Database System u Transactions To search for a book with specific title and/or specific (first) author To place a hold request on a book and to be notified either by email or by post when the book is returned To generate letters or send emails to members with overdue books 16 Shuhua Ruan, School of Software, Sichuan University

17. A Library Database System u Transactions These interactions with the database system both query and update the database and these database manipulations are specified in the application programs. 17 Shuhua Ruan, School of Software, Sichuan University

18. A Library Database System u Integrity Constraints The database can also be used to enforce the rules of the library. It prevents a library member from borrowing any book if they have already borrowed 5 books or failed to return overdue books. 18 Shuhua Ruan, School of Software, Sichuan University

19. An E-Store Database System u In general, the goal of the e-store database is to maintain detailed information about: products for sale customer information customers' shopping baskets customers' purchase orders 19 Shuhua Ruan, School of Software, Sichuan University

20. An E-Store Database System 20 Shuhua Ruan, School of Software, Sichuan University

21. An E-Store Database System u Transactions To search for a specific product or browse through a particular category by querying the database. customer-registration program place-order program shipping application 21 Shuhua Ruan, School of Software, Sichuan University

22. An E-Store Database System u Transactions The operations of the e-store are implemented by several application programs that interact with the customers via a Web browser and manipulate the e-store database. 22 Shuhua Ruan, School of Software, Sichuan University

23. An E-Store Database System u Integrity Constraints E-store business rules can be specified as integrity constraints. A simple example is that the shipping date cannot be earlier than the purchase date. Another is that an order cannot be shipped without a credit card authorization number recorded in the database. 23 Shuhua Ruan, School of Software, Sichuan University

24. Database System Architectures 24 Shuhua Ruan, School of Software, Sichuan University

25. Database System Architectures 25 Shuhua Ruan, School of Software, Sichuan University

26. The History of the Development of DBMSs u There are two approaches to data storage and use. One is the file- based system and the other the database approach. In fact, the file- based system is the predecessor to the DBMS. However, there was never a time when the database approach began and the file-based system ceased. And the file-based system still exists in specific areas. Shuhua Ruan, School of Software, Sichuan University 26

27. The History of the Development of DBMSs u It has been suggested that the DBMS has its roots in the 1960s Apollo moon-landing project, which was initiated in response to President Kennedy's objective of landing a man on the moon by the end of that decade. Shuhua Ruan, School of Software, Sichuan University 27

28. The History of the Development of DBMSs u At that time there was no system available that would be able to handle and manage the vast amounts of information that the project would generate. As a result, North American Aviation (NAA, now Rockwell International), developed software known as GUAM (Generalized Update Access Method). Shuhua Ruan, School of Software, Sichuan University 28

29. The History of the Development of DBMSs u GUAM was based on the concept that smaller components come together as parts of large ones, and so on, until the final product is assembled. In the mid-1960s, IBM joined NAA to develop GUAM into what is now known as IMS (Information Management System). Shuhua Ruan, School of Software, Sichuan University 29

30. The History of the Development of DBMSs u Database systems are classified according to the way they represent data, i.e., on their provided data model. u Broadly speaking, data models are classified into record-oriented and object-oriented models. Shuhua Ruan, School of Software, Sichuan University 30

31. The History of the Development of DBMSs u There are three standardized record- oriented data models, Hierarchical Data Model Network Data Model Relational Data Model Shuhua Ruan, School of Software, Sichuan University 31

32. The History of the Development of DBMSs u Although there is not a single object- oriented data model standard, there are two objected-based approaches: Object-Relational Data Model Object-Oriented Data Model Shuhua Ruan, School of Software, Sichuan University 32

33. The History of the Development of DBMSs u There are three phases: The First Generation Hierarchical Data Model Network Data Model The Second Generation Relational Data Model The Third Generation Object-Relational Data Model Object-Oriented Data Model Shuhua Ruan, School of Software, Sichuan University 33

34. Two Core Concepts of Database Systems u If one were to divide the idea of a database system into its two core concepts, these would be the data model, which supports data abstraction, and the notion of transaction, which supports reliability and efficiency. Shuhua Ruan, School of Software, Sichuan University 34

35. Two Core Concepts of Database Systems u Data abstraction, reliability and efficiency are the three characteristics of DBMSs. These three features of the database system approach explain the advantages it has over the older file system approach as a means of storing and managing data. Shuhua Ruan, School of Software, Sichuan University 35

36. Two Core Concepts of Database Systems u Data Models Database systems make it possible for the data to remain relatively independent of the applications that access and manipulate it. This independence is achieved through a process of data abstraction. A fundamental concept underlying data abstraction in databases is the data model. Shuhua Ruan, School of Software, Sichuan University 36

37. Two Core Concepts of Database Systems u Data Models A data model defines how the data is organized and manipulated in a database. Shuhua Ruan, School of Software, Sichuan University 37

38. an example of a data model for a learning system Shuhua Ruan, School of Software, Sichuan University 38

39. Two Core Concepts of Database Systems u Transactions A Logical Unit of Work on the Database A transaction is the execution of a program segment that performs some function or task by accessing a shared database. Shuhua Ruan, School of Software, Sichuan University 39

40. Two Core Concepts of Database Systems u Transactions ACID Properties Atomicity Consistency Isolation Durability Shuhua Ruan, School of Software, Sichuan University 40

41. Two Core Concepts of Database Systems u Transactions A DBMS supports the ACID properties of transactions by implementing three different sets of algorithms. Shuhua Ruan, School of Software, Sichuan University 41

42. Two Core Concepts of Database Systems u Transactions three different sets of algorithms Concurrency Control Protocols, ensures the isolation property. Recovery Protocols, ensures atomicity and durability properties. Triggering and Asserting Mechanisms, enforces the integrity constraints on a database. Shuhua Ruan, School of Software, Sichuan University 42

43. a 2PL execution for concurrency control protocols Shuhua Ruan, School of Software, Sichuan University 43