1Chapter 1

2Chapter 1

Database Application System & Database Application System & Database ManagementDatabase Management

Definitions Disadvantages of File Processing Database Management System Advantages of the Database Approach Three-Level Database Architecture Program-Data Independence Data and Metadata Data Dictionary Evolution of Database Systems

3Chapter 1

DefinitionsDefinitions

– Data: Meaningful facts, text, graphics, images, sound,

video segments.

Data in Context

4Chapter 1

DefinitionsDefinitions

– Database: An organized collection of logically related data.

– Information: Data processed to be useful in decision making.

– Metadata: Data that describes data.

5Chapter 1

Disadvantages of Disadvantages of File Processing SystemsFile Processing Systems

Program-Data Dependence– All programs maintain metadata for each file they use

Data Redundancy (Duplication of data)– Different systems/programs have separate copies of the same data

Limited Data Sharing– No centralized control of data

Lengthy Development Times– Programmers must design their own file formats

Excessive Program Maintenance– 80% of of information systems budget

6Chapter 1

Database Management Database Management SystemSystem

– A DBMS is a data storage and retrieval system which permits data to be stored

non-redundantly while making it appear to the user as if the data is well-integrated.

7Chapter 1

Database Management Database Management SystemSystem

8Chapter 1

Advantages of the Database Advantages of the Database ApproachApproach

a) Program-Data Independence: The separation of data descriptions (metadata) from

the application programs that use the data is called data independence. This property of database systems allows an organization's data to change and evolve (within limits) without changing the application programs that process the data.

9Chapter 1

Advantages of the Database Advantages of the Database ApproachApproach

Problems with Data Dependency Each application programmer must maintain their

own data. Each application program needs to include code

for the metadata of each file. Each application program must have its own

processing routines for reading, inserting, updating and deleting data.

Lack of coordination and central control Non-standard file formats

10Chapter 1

Advantages of the Database Advantages of the Database ApproachApproach

b) Minimal Data Redundancy : The design goal with the database approach is that

previously separate (and redundant) data files are integrated into a single, logical structure. Each primary fact is recorded (ideally) in only one place in the database. For example, the fact that the product with Product_ID 3 is an oak computer desk with a unit price of $375.00 is recorded in one place in the Product table

11Chapter 1

Advantages of the Database Advantages of the Database ApproachApproach

c) Improved Data Consistency : By eliminating (or controlling) data redundancy, we

greatly reduce the opportunities for inconsistency. For example, if a customer address is stored only once, we cannot have disagreement on the stored values.

12Chapter 1

Advantages of the Database Advantages of the Database ApproachApproach

d) Improved Data Sharing : A database is designed as a shared corporate

resource. Authorized users are granted permission to use the database, and each user (or group users) is provided one or more user views to facilitate this use.

13Chapter 1

Advantages of the Database Advantages of the Database ApproachApproach

e) Increased Productivity of Application Development :

A major of the database approach is that it greatly reduces the cost and time for developing new business applications.

f) Enforcement of Standards When the database approach is implemented with full

management support, the database administration function should be granted single-point authority and responsibility for establishing and enforcing data standards

14Chapter 1

Advantages of the Database Advantages of the Database ApproachApproach

g) Improved Data Quality : The database approach provides a number of tools

and processes to improve data quality

h) Improved Data Accessibility and Responsiveness

With a relational database, end users without programming experience can often retrieve and display data, even when it crosses traditional departmental boundaries

15Chapter 1

Advantages of the Database Advantages of the Database ApproachApproach

i) Reduced Program Maintenance : Stored data must be changed frequently for a variety

of reasons: new data item types are added, data formats are changed, and so on. In a database environment, data are more independent of the application programs that use them. Within limits, we can change either the data or the application programs that use the data without necessitating a change in the other factor. As a result, program maintenance can be significantly reduced in a modern database environment

16Chapter 1

Database ArchitectureDatabase Architecture

generalized framework proposed by ANSI/SPARC Committee

3 levels– External– Conceptual– Internal

17Chapter 1

3 Levels in Architecture of a 3 Levels in Architecture of a DBMSDBMS

External level– consists of the user (group) views of the database– each user will have its own view of the database

18Chapter 1

External level of DBMSExternal level of DBMS

Concern with the way the data is viewed by individual user- application programmer or on-line terminal user

for application programmer- language such as VB, VC, powerbuilder, COBOL

19Chapter 1

3 Levels in Architecture of a 3 Levels in Architecture of a DBMSDBMS

Conceptual level– involves analysis of users’ information needs

and definition of data items needed to meet them

– the result of the conceptual design is the conceptual schema, a single, logical description of all data elements and their relationships

20Chapter 1

Conceptual level of DBMSConceptual level of DBMS

Level of indirection between internal and external level a representation of the entire information content of the

database consists of multiple occurrences of multiple types of

conceptual record

21Chapter 1

3 Levels in Architecture of DBMS3 Levels in Architecture of DBMS

Internal Level– provides the physical view of the database- the disk

drives, physical address, indexes, pointers and so on.– This level is the responsibility of physical database

designers.

22Chapter 1

Internal level of DBMSInternal level of DBMS

Concern with the way the data is physically stored low-level representation of the entire database internal record is same as stored record

23Chapter 1

3 Levels in Architecture of a 3 Levels in Architecture of a DBMSDBMS

24Chapter 1

Program-Data Program-Data IndependenceIndependence

– Separation of data description from application program

– Data description are stored in central location called repository

– Allows organization’s data to change without changing the application program

25Chapter 1

Data and Meta-dataData and Meta-data

Data– meaningful facts, text, graphics, images, sound etc.

Metadata– describe the properties / characteristics of other data.

include data definitions and data structures. Example on Class Roster, the metadata show

– data item name,

– data type, length,

– minimum and maximum allowable values

– description of each item

26Chapter 1

Data Item Value----------------------------------- -----------------------

Name Type Length Min Max Description

Course Alphanumeric 30     Course ID and name

Section Integer 1 1 9 Section number

Semester Alphanumeric 10     Semester and year

Name Alphanumeric 30     Student name

ID Integer 9     Student ID (SSN)

Major Alphanumeric 4     Student major

GPA Decimal 3 0.0 4.0 Student grade point average

27Chapter 1

Data DictionaryData Dictionary

– A repository of information about a database which documents data elements of a database.

– An integral part of relational DBMSs is the data dictionary, which stores metadata, or information about the database, including attribute names and definitions for each table in the database.

28Chapter 1

Components of the Components of the Database EnvironmentDatabase Environment

CASE Tools – computer-aided software engineering Repository – centralized storehouse of metadata Database Management System (DBMS) – software for managing

the database Database – storehouse of the data Application Programs – software using the data User Interface – text and graphical displays to users Data Administrators – personnel responsible for maintaining the

database System Developers – personnel responsible for designing databases

and software End Users – people who use the applications and databases

29Chapter 1

Figure 1-10 Components of the database environment

30Chapter 1

Evolution of DB SystemsEvolution of DB Systems

Flat files - 1960s - 1980s Hierarchical – 1970s - 1990s Network – 1970s - 1990s Relational – 1980s - present Object-oriented – 1990s - present Object-relational – 1990s - present Data warehousing – 1980s - present Web-enabled – 1990s - present