1. Database Systems: Design, Implementation, and Management THIRD EDITION
CHAPTER 1
File Systems and Databases 1

2. Chapter Objectives Understand characteristics of a file system
Understand advantages of using a database
Understand characteristics of database systems
Understand basic database concepts
Understand three different types of database models 2

3. Chapter Overview 1.1 Introducing the Database
1.2 The Historical Roots of the Database: Files and File Systems
1.3 A File System Critique
1.4 Database Systems
1.5 Database Models 3

4. Introducing the Database
Major Database Concepts
Data
Data management
Database
Metadata
Database management system (DBMS) 4

5. Introducing the Database
Importance of DBMS
It helps make data management more efficient and effective.
Its query language allows quick answers to ad hoc queries.
It provides end users better access to more and better-managed data.
It promotes an integrated view of organization operations -- ig picture?
It reduces the probability of inconsistent data. 5

6. Introducing the Database
Figure 1.1 The DBMS Manages the Interaction between the End User and the Database 6

7. Introducing the Database
Why Database Design Is Important?
A poorly designed database is a breeding ground for uncontrolled data redundancies.
A poorly designed database generates errors that lead to bad decisions.
A Practical Approach to Database Design
Focus on principles and concepts of practical database design
Use of two complete applications through the logical design stage 7

8. Historical Roots Why Studying File Systems?
It provides historical perspective.
It teaches lessons to avoid pitfalls of data management.
Its simple characteristics facilitate understanding of the design complexity of a database.
It provides useful knowledge for converting a file system to a database system. 8

9. Historical Roots
Table 1.1 Basic File Terminology 10

10. Historical Roots
Reports Prepared by DP Specialist Using the CUSTOMER file:
Monthly summaries of types and amounts of insurance sold by each agent
Monthly checks to determine which customers must be contacted for renewal
Analysis reports on ratios of insurance types sold by each agent
Customer contact letters with coverage summary and customer relation bonuses 11

11. Historical Roots
Figure 1.2 A Simple File System 13

12. File System Critique File System Data Management
File systems require extensive programming in 3GL.
As file systems become more complex, managing files gets more difficult.
Making changes in existing file structures is important and difficult.
Data access programs are subject to change with file structure changes (structural dependence).
Security features are difficult to implement and are lacking. 14

13. File System Critique Structural and Data Dependence
Structural Dependence
A change in any file structure requires the modification of all programs using that file.
Data Dependence
A change in any file data characteristics requires changes of all data access programs.
Data dependence makes file systems extremely cumbersome from a programming and data management point of view. 15

14. File System Critique Field Definitions and Naming Conventions
A good (flexible) record definition anticipates reporting requirements by breaking up fields into their components.
Example:
Customer Name  Last Name, First Name, Initial
Customer Address  Street Address, City, State
Selecting proper field names is very important.
Descriptive
Self-documenting 16

15. File System Critique
Data Redundancy: Uncontrolled data redundancy sets the stage for
Data Inconsistency (lack of data integrity)
Data anomalies
Modification anomalies
Insertion anomalies
Deletion anomalies 17

16. Database Systems
In a database system, logically related data are stored in a single data repository.
The database represents a change in the way end user data are stored, accessed, and managed.
DBMS makes it easier to eliminate most of the file system data inconsistency, data anomalies, and data structural dependency problems.
Current DBMS stores not only the data structure, but also the relationships.
DBMS takes care of defining all the required access paths. 18

17. Database Systems
Figure 1.3 Contrasting Database and File System Designs 19

18. Database Systems
Figure 1.4 The Database System Environment 20

19. Database Systems The Database System Components Hardware Software
Computer
Peripherals
Software
Operating systems software
DBMS software
Applications programs and utilities software 21

20. Database Systems The Database System Components People Procedures Data
Systems administrators
Database administrators
Database designers
Systems analysts and programmers
End users
Procedures
Instructions and rules that govern the design and use of the database system
Data
Collection of facts stored in the database 22

21. Database Systems Database Systems and Organizational Factors
The complexity of database systems depends on various organizational factors:
Organization size
Organization function
Organization corporate culture
Organizational activities and environment
Database solutions must be cost effective and strategically effective. 23

22. Database Systems Types of Database Systems Number of Users Scope
Single-user
Multi-user
Scope
Desktop
Workgroup
Enterprise 24

23. Database Systems Types of Database Systems Location Use Centralized
Distributed
Use
Transactional (Production)
Decision support
Data warehouse 25

24. Database Systems DBMS Functions Data Dictionary Management
Data dictionary stores definitions of the data elements and their relationships (metadata).
It provides data abstraction and removes structural and data dependency from the system.
Data Storage Management
DBMS creates data storage structure and relieves us from the task of defining and programming physical data characteristics. 26

25. Database Systems DBMS Functions Data Transformation and Management
DBMS relieves us from the chore of making distinction between logical format and physical format of data.
Security Management
DBMS provides user security and data privacy within the database.
Data security is especially important in multi-user database. 27

26. Database Systems DBMS Functions Multi-User Access Control
DBMS ensures that multiple users can access the database concurrently and still guarantees the integrity of the database.
Backup and Recovery Management
DBMS provides backup and recovery procedures to ensure data safety and integrity.
Data Integrity Management
DBMS promotes and enforces integrity rules to eliminate data integrity problems.
Ensuring data integrity is especially important in transaction-oriented database systems. 28

27. Database Systems Managing the Database System: Shift in Focus
The role of DP specialists or manager changes from a programming emphasis to focus on the broader management aspects of the organization data resource and on the administration of complex database software.
Shift in DP Personnel
DP Manager
Systems Administrator
Database Administrator 29

28. Database Models
A database model is a collection of logical constructs used to represent the data structure and the data relationships found within the database.
Two Categories of Database Models
Conceptual models focus on the logical nature of the data representation. They are concerned with what is represented rather than how it is represented.
Implementation models place the emphasis on how the data are represented in the database or on how the data structures are implemented. 30

29. Database Models
Three Types of Relationships in Conceptual Database Models
One-to-many relationships 31

30. Database Models
Three Types of Relationships in Conceptual Database Models
Many-to-many relationships 32

31. Database Models
Three Types of Relationships in Conceptual Database Models
One-to-one relationships 33

32. Database Models Three Types of Implementation Database Models
Hierarchical database model
Network database model
Relational database model 34

33. Database Models Hierarchical Database Model Background
GUAM (Generalized Update Access Method) was developed by North American Rockwell.
It conformed to upside-down tree structure -- hierarchical structure.
Information Management System (IMS) -- Jointly developed by IBM and Rockwell.
Hierarchical database model concepts for the basis for subsequent database development.
Its limitations lead to a different way of looking at database design. 35

34. Database Models
Figure 1.5 A Hierarchical Structure 36

35. Database Models Hierarchical Database Model Basic Structure
Collection of records perceived as organized to conform to the upside-down tree structure.
A tree structure is represented as a hierarchical path on the computer storage media.
One-to-Many (1:M) Relationship
Each parent can have many children.
Each child has only one parent. 37

36. Database Models
Figure 1.6 The Basic Components of a Hierarchical Structure 38

37. Database Models Hierarchical Database Model Advantages
Data sharing and security provision
Data independence -- Reduced programming and maintenance effort
Database integrity
Efficiency dealing with a large database
Large installed (mainframe) base
Abundant business applications 39

38. Database Models Hierarchical Database Model Disadvantages
Requirement of knowledge of physical level of data storage
Inability to represent relationships that do not conform to the hierarchical 1:M standard
Complex and inflexible to manage
Time consuming and complicated application programming
Lack of ad hoc query capability for end users
Lack of standard concepts and implementation -- limited portability
Requirement of extensive programming activities 40

39. Database Models Network Database Model Background
CODASYL (Conference on Data Systems Language) group created DataBase Task Group (DBTG) in 1971.
DBTG specified three crucial database components:
Network schema defines the conceptual organization of the entire database as viewed by the database administrator.
Subschema defines the portion of the database as seen by the applications programs.
Data Management Language defines the data characteristics and the data structure and to manipulate the data. 41

40. Database Models Network Database Model Background
Three DBTG data management language components:
Schema Data Definition Language (DDL)
Subschema Data Definition Language
Data Manipulation Language
ANSI SPARC (Standards Planning And Requirements Committee) augmented the database standards in 1975. 42

41. Database Models Network Database Model Basic Structure
Set -- A relationship is called a set. Each set is composed of at least two record types: an owner (parent) record and a member (child) record.
Figure 1.7 A Set 43

42. Database Models
Figure 1.8 A Network Model 44

43. Database Models Network Database Model
Relationships among the records are decomposed into a series of sets.
Figure 1.9 Defining Set Components 45

44. Database Models Network Database Model Advantages
Easier implementation of M:N relationships
Superior data access type and flexibility
Enforced data integrity
Sufficient data independence 46

45. Database Models Network Database Model Disadvantages
Difficult to design and use properly
Difficult to make changes in a database
Very complex structure from the application programmer point of view
Complex navigational data access environment 47

46. Database Models Relational Database Model Background
E. F. Codd developed the relational model in 1970.
Conceptually simple but versatile
Major breakthrough for both users and designers
From tandard transmission?to utomatic transmission
Requires more computing power
Considered impractical in the 1970
Modern computers (even PCs) are powerful enough to handle relational databases. 48

47. Database Models Relational Database Model Basic Structure
Relational DataBase Management System (RDBMS)
RDBMS allows user/designer operate in a human logical environment.
Relational database is perceived by the user as a collection of tables in which data are stored.
Each table consists of series of row/column intersections.
Tables (or relations) are related to each other by sharing a common entity characteristic.
The relationship type is often shown in a relational schema.
A table yields complete data and structural independence because it is a purely logical structure. 49

48. Database Models Relational Database Model
Figure 1.10 A Relational Schema 51

49. Database Models Relational Database Model Advantages
Data independence and structural independence
Easy to design the database and to manage its contents
Less programming effort required
Powerful and flexible query capability:
Structured Query Language (SQL)
Fourth Generation Language (4GL)
Specify hat to do?not ow to do
Introduced by IBM in 1974
3 parts: (1) User interface, (2) Set of tables (3) SQL engine 52

50. Database Models Relational Database Model Disadvantages
RDBMS requires substantial hardware and operating system overhead.
It tends to be slower than other database systems. 53