1. Architecture for a Database System
ITD1312 Database Principles
Database Concepts and
Architecture for a Database System

2. Database Application System & Database 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

3. Definitions Data: Data in Context
Meaningful facts, text, graphics, images, sound, video segments.
Data in Context

4. Definitions Database: Information: Metadata:
An organized collection of logically related data.
Information:
Data processed to be useful in decision making.
Metadata:
Data that describes data.

5. Disadvantages of File 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

6. Database Management System
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.

7. Database Management System

8. Advantages of the Database Approach
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.

9. Advantages of the Database Approach
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

10. Advantages of the Database Approach
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 $ is recorded in one place in the Product table

11. Advantages of the Database Approach
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.

12. Advantages of the Database Approach
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.

13. Advantages of the Database Approach
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

14. Advantages of the Database Approach
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

15. Advantages of the Database Approach
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

16. Database Architecture
generalized framework proposed by ANSI/SPARC Committee
3 levels
External
Conceptual
Internal

17. 3 Levels in Architecture of a DBMS
External level
consists of the user (group) views of the database
each user will have its own view of the database

18. External 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

19. 3 Levels in Architecture of a DBMS
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

20. Conceptual 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

21. 3 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.

22. Internal 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

23. 3 Levels in Architecture of a DBMS

24. Program-Data Independence
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

25. Data and Meta-data Data Metadata
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

26. ----------------------------------- -----------------------
Data Item Value
Name
Type
Length
Min
Max
Description
Course
Alphanumeric 30
Course ID and name
Section
Integer 1 9
Section number
Semester 10
Semester and year
Student name ID
Student ID (SSN)
Major 4
Student major
GPA
Decimal 3
0.0
4.0
Student grade point average

27. Data 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.

28. Components of the Database 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

29. Figure 1-10 Components of the database environment

30. Evolution of DB Systems
Flat files s s
Hierarchical – 1970s s
Network – 1970s s
Relational – 1980s - present
Object-oriented – 1990s - present
Object-relational – 1990s - present
Data warehousing – 1980s - present
Web-enabled – 1990s - present