Download INSS 651

INSS 651
Chapter 1
Learning Objectives
• To develop the main database system concepts.
• To show the evolution of database systems from
computer file systems.
• To show that database design is a crucial first
step in the development and proper use of
database systems.
• To understand the main DBMS functions.
• To describe the database environment.
• To introduce the student to the basics of different
types of database systems.
What is a Database?
A database is a SHARED collection of LOGICALLY RELATED and
INTEGRATED data, designed to meet the INFORMATION NEEDS
of multiple users in the org.
. allows sharing
. reduces duplication
. end user data
Metadata:
data about data
Think of Airline database, Motor vehicle database
WHY DATABASES?
•
•
•
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Good way of managing data
Quick retrieval of data
Ad-hoc capabilities
Access to "desired" data
.Quality
.Quantity
• Data Consistency
DBMS
A collection of programs which
• Manages database structure
• Control Data Access
• Intermediary between user and the
database
DB Design
A way of manipulating data in the
database
• create database structure also known
as "logical db design"
• a poorly designed system can lead to
– redundancy
– inconsistency
– data errors
File System
File System:
one file for one application
• Customer
• Sales
• Agent
Query:
• Give the name of all customers
• Give the names of all customers of agent SMITH
Problems with file systems
•
•
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•
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.REDUNDANCY
.INCONSISTENT DATA
.INFLEXIBILITY
.PROGRAM/DATA DEPENDENCE
.LIMITED DATA SHARING
.LITTLE STANDARDS
.EXCESSIVE MAINTENANCE
DATABASE APPROACH
• REDUCED/CONTROLLED DATA
REDUNDANCY
• COMPATIBLE DATA
• DATA INTEGRITY
• PROGRAM/DATA INDEPENDENCE
• SHARING OF DATA
• FLEXIBLE DATA
• EASE OF APPLICATION DEVELOPMENT
• BETTER DATA MANAGEMENT
• SECURITY
COSTS OF DATABASE
APPROACH
• EXPENSIVE
• BACKUPS AND RECOVERY
• NEW SPECIALIZED PERSONNEL
• DATA OWNERSHIP
Components of a Database
Environment
1. HARWARE
.Physical Devices
.Computer
.Peripherals
.Network
2. SOFTWARE
Operating System
DBMS
3. Application Programs &Utilities
3.PERSONNEL:
.DBA
. responsible for maintaining data base
. create standards
. resolve conflicts
.DB Designers
.Design DB structure
.System Analysts & Programmers
.design and implement application programs
END USERS:
Interaction MODE:
.DIRECT
.ad-hoc mode
.query
.INDIRECT
.through application programs
.embedded in host languages
EU OPERATIONS:
.ADD
.DELETE
.MODIFY
.RETRIEVE
4. PROCEDURES:
standards, procedures and rules that govern
the design and usage of DB systems
5.DB (REPOSITORY)
A shared and integrated collection of related data necessary
to Satisfy users
It contains:
.
actual data
.
information about
.
structure of data
.
relationship among data items
TYPES OF DATABASES
CENTRALIZED
greater control
vulnerable to failure
many cases impractical
.all-in-one
.large
.high usage
DISTRIBUTED
database is spread physically across computers in
multiple locations
practical because of organizational Structure
concurrency and security problems
DBMS FUNCTIONS:
..Data Dictionary Mgt
..Data Storage Mgt
..Data Transformation
..Security Mgt
..Multi User Access Control
..Backup & recovery Mgt
..Data Integrity Mgt
..DDL & DML
..Data Communication Interface
...allows data access through computer network environment
...interface with web
..accept user data thru web
..publish report on web
..distribute information to third party thru e-mail
• Q5/P62
Ch 2: Data Models
DB Model
• Represents data structure and
relationship
• Conceptual
"What" is represented
• Implementation
“How" represented
Basic Building Blocks
CONCEPTUAL: 3 types of associations:
one to many (1:m)
many to many (m:n)
one-to-one (1:1)
Constraints & Business Rules (BR)
Constraints are restrictions
BR is a
Policy
Procedure
principle
Implementation
How data is represented in database?
Hierarchical (see page 34)
Network (see page 35)
..Simple
..Complex
Relational (page 36)
Object-oriented
Hierarchical DB Model:
(mimics tree structure)
IMS by IBM
basic unit is SEGMENT
(similar to a record)
..root
..a child can have at the most one parent
..a parent can have many children
..need to provide navigation path
.pre order traversing
.post order traversing
Advtg:
. allows data sharing
.data independence
.data integrity
.efficient processing
Disadvtg:
.need to know some PHYSICAL level details
.data that do not conform to 1:m
.complex and less flexible
.need to provide navigational path
.ad-hoc capabilities limited
Network DB model:
basis is a SET
set has OWNER and MEMBERS
a set can have many members
a set can have many ONERS and MEMBERS
Advtgs:
.m:n easy to implement
.data integrity is maintained
.data independence
Disadvtg:
.Complex
.no structural independence
.navigation path
Relational Model:
no need to know STRUCTURAL details of the data
relation (tables) environment
easy to understand
RDBMS
1:1, 1:m, m:n easy to implement
standardized SQL
Linking relational tables (page 37)
Typically done through primary and foreign key
Object-Oriented Model:
Objects are defined (similar to entities)
Objects contain data and procedures
Objects can FIT with other objects
Objects are reusable
Objects have INHERITANCE property
ER Data Model (page 38)
Define
Entities
Attributes
Relationships
Ex:
Teacher
Student
Degree of DATA abstraction
(see figure 2.9/p46)
• Conceptual IT (hardware/software
independent)
• Internal (DBMS dependent)
• External (end user orientation)
• Physical Model (actual implementation)
Q5/p53, Q25/p56
Supplemental reading:
• www.itpapers.com