1. Chapter 1 File Systems and Databases
Database Systems: Design, Implementation, and
Management, 4th Edition
Peter Rob & Carlos Coronel

2. Introducing the Database
Major Database Concepts
Data and information
Data - Raw facts
Information - Processed data
Data management
Database
Metadata
Database management system (DBMS)

3. Sales per Employee for Each of ROBCOR’S Two Divisions
Figure 1.1

4. 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’s operations -- “big picture.”
It reduces the probability of inconsistent data.

5. Figure 1.2 The DBMS Manages the Interaction
Between the End User and the Database
Figure 1.2

6. Introducing the Database
Why Database Design Is Important?
A well-designed database facilitates data management and becomes a valuable information generator.
A poorly designed database is a breeding ground for uncontrolled data redundancies.
A poorly designed database generates errors that lead to bad decisions.

7. Historical Roots Why Study 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. Contents of the CUSTOMER File
Figure 1.3

9. Table 1.1 Basic File Terminology

10. Contents of the AGENT File
Figure 1.4

11. A Simple File System
Figure 1.5

12. File System Critique File System Data Management
File systems require extensive programming in a third-generation language (3GL).
As the number of files expands, system administration becomes difficult.
Making changes in existing file structures is important and difficult.
Security features to safeguard data are difficult to program and usually omitted.
Difficulty to pool data creates islands of information.

13. File System Critique Structural and Data Dependence
Structural Dependence
A change in any file’s structure requires the modification of all programs using that file.
Data Dependence
A change in any file’s data characteristics requires changes in all data access programs.
Significance of data dependence is the difference between the data logical format and the data physical format.
Data dependence makes file systems extremely cumbersome from a programming and data management point of view.

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

15. File System Critique Field Definitions and Naming Conventions
Selecting proper field names is very important.
Names must be as descriptive as possible within restrictions.
Naming must reflect designer’s documentation needs and user’s reporting and processing requirements.

16. 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. Figure 1.6

18. The Database System Environment
Figure 1.7
Figure 1.7

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

20. Database Systems The Database System Components People Procedures Data
Systems administrators
Database administrators (DBAs)
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

21. Database Systems The Database System Components
The complexity of database systems depends on various organizational factors:
Organization’s size
Organization’s function
Organization’s corporate culture
Organizational activities and environment
Database solutions must be cost effective AND strategically effective.

22. Database Systems Types of Database Systems Number of Users Scope
Single-user
Desktop database
Multiuser
Workgroup database
Enterprise database
Scope
Desktop
Workgroup
Enterprise

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

24. Database Systems DBMS Functions 1. Data Dictionary Management
2. Data Storage Management
3. Data Transformation and Presentation
4. Security Management
5. Multi-User Access Control
6. Backup and Recovery Management
7. Data Integrity Management
8. Database Access Languages (DDL and DML) and Application Programming Interfaces
9. Database Communication Interfaces

25. 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.

26. Database Models Three Types of Relationships
One-to-many relationships (1:M)
A painter paints many different paintings, but each one of them is painted by only that painter.
PAINTER (1) paints PAINTING (M)
Many-to-many relationships (M:N)
An employee might learn many job skills, and each job skill might be learned by many employees.
EMPLOYEE (M) learns SKILL (N)
One-to-one relationships (1:1)
Each store is managed by a single employee and each store manager (employee) only manages a single store.
EMPLOYEE (1) manages STORE (1)

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

28. A Hierarchical Structure
Figure 1.8

29. Database Models Hierarchical Database Model Basic Structure
Collection of records logically organized to conform to the upside-down tree (hierarchical) structure.
The top layer is perceived as the parent of the segment directly beneath it.
The segments below other segments are the children of the segment above them.
A tree structure is represented as a hierarchical path on the computer’s storage media.

30. Database Models Hierarchical Database Model Advantages Disadvantages
Conceptual simplicity
Database security
Data independence
Database integrity
Efficiency dealing with a large database
Disadvantages
Complex implementation
Difficult to manage
Lacks structural independence
Applications programming and use complexity
Implementation limitations
Lack of standards

31. Child with Multiple Parents
Figure 1.9

32. 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.
A set is represents a 1:M relationship between the owner and the member.

33. A Network Database Model
Figure 1.10

34. Database Models Network Database Model Advantages Disadvantages
Conceptual simplicity
Handles more relationship types
Data access flexibility
Promotes database integrity
Data independence
Conformance to standards
Disadvantages
System complexity
Lack of structural independence

35. Database Models Relational Database Model Basic Structure
RDBMS allows operations in a human logical environment.
The relational database is perceived as a collection of tables.
Each table consists of a 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.

36. Linking Relational Tables
Figure 1.11

37. Database Models Relational Database Model Advantages Disadvantages
Structural independence
Improved conceptual simplicity
Easier database design, implementation, management, and use
Ad hoc query capability (SQL)
Powerful database management system
Disadvantages
Substantial hardware and system software overhead
Possibility of poor design and implementation
Potential “islands of information” problems

38. A Relational Schema
Figure 1.12

39. Database Models Entity-Relationship Data Model
It is one of the most widely accepted graphical data modeling tools.
It graphically represents data as entities and their relationships in a database structure.
It complements the relational data model concepts.

40. Database Models Entity Relationship Data Model Basic Structure
E-R models are normally represented in an entity relationship diagram (ERD).
An entity is represented by a rectangle.
Each entity is described by a set of attributes. An attribute describes a particular characteristics of the entity.
A relationship is represented by a diamond connected to the related entities.

41. Figure 1.13 Relationship Depiction: The ERD

42. Figure 1.14 Relationship Depiction: The Crow’s Foot

43. Database Models Entity-Relationship Data Model Advantages
Exceptional conceptual simplicity
Visual representation
Effective communication tool
Integrated with the relational database model
Disadvantages
Limited constraint representation
Limited relationship representation
No data manipulation language
Loss of information content

44. Database Models Object-Oriented Database Model Characteristics
An object is described by its factual content.
An object includes information about relationships between the facts within the object, as well as with other objects.
An object is a self-contained building block for autonomous structures.

45. Database Models Object-Oriented Database Model Basic Structure
Objects are abstractions of real-world entities or events.
Attributes describe the properties of an object.
Objects that share similar characteristics are grouped in classes.
A class is a collection of similar objects with shared structure (attributes) and behavior (methods).
Classes are organized in a class hierarchy.
An object can inherit the attributes and methods of the classes above it.

46. A Comparison: The OO Data Model and the ER Model
Figure 1.15

47. Database Models Object-Oriented Database Model Advantages
Add semantic content
Visual presentation includes semantic content
Database integrity
Both structural and data independence
Disadvantages
Lack of OODM standards
Complex navigational data access
Steep learning curve
High system overhead slows transactions

48. The Development of Data Models
Figure 1.16

49. Wrap-Up: The Evolution of Data Models
Common characteristics required for data models:
A data model must show some degree of conceptual simplicity without compromising the semantic completeness.
A data model must represent the real world as closely as possible.
The representation of the real-world transformations (behavior) must be in compliance with the consistency and integrity characteristics of any data model.

50. Wrap-Up: The Evolution of Data Models
Database Models and the Internet
The use of the Internet as a prime business tool is shifting focus to database products that interface efficiently and easily with the Internet.
Successful “Internet age” databases are characterized by:
Flexible, efficient, and secure Internet access.
Support for complex data types and relationships.
Seamless interfacing with multiple data sources and structures.
Simplicity of the conceptual database model.
An abundance of available database tools.
A powerful DBMS to help make the DBA’s job easier.