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? 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.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

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

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