Chapter2databaseenvironment 120307033742-phpapp01

Database Systems 1
Chapter 2 :Chapter 2 :
DatabaseDatabase
EnvironmentEnvironment

Database Systems 2
Learning Outcomes
At the end of this chapter, students will be able to:
 Describe ANSI/SPARC Architecture
 Described roles in database environment
 Describe data models & conceptual modeling

Database Systems 3
Objectives of Three-Level Architecture
 All users should be able to access same
data.
 A user's view is immune to changes made
in other views.
 Users should not need to know physical
database storage details.

Database Systems 4
Objectives of Three-Level Architecture
 DBA should be able to change database
storage structures without affecting the
users' views.
 Internal structure of database should be
unaffected by changes to physical aspects
of storage.
 DBA should be able to change conceptual
structure of database without affecting all
users.

Database Systems 5
ANSI-SPARC Three-Level Architecture
ANSI - American
National Standards
Institute
SPARC - Standards
Planning and
Requirements
Committee

Database Systems 6
ANSI-SPARC Three-Level Architecture
 External Level
 Users’ view of the database.
 Describes that part of database that is relevant to a
particular user.
 Conceptual Level
 Community view of the database.
 Describes what data is stored in database and
relationships among the data.
 Internal Level
 Physical representation of the database on the
computer.
 Describes how the data is stored in the database.

Database Systems 7
Differences between Three Levels of
ANSI-SPARC Architecture

Database Systems 8
Data Independence and the ANSI-
SPARC Three-Level Architecture
Data Independence: structure of
organization and data format which are
stored physically in storage are independent
from its application.
Specifically, data independence means
changes in storage structure and data
access technique does NOT affect
application program.

Database Systems 9
Data Independence and the ANSI-
SPARC Three-Level Architecture

Database Systems 10
Data Independence
 Logical Data Independence
 Refers to immunity of external schemas to changes in
conceptual schema.
 Conceptual schema changes (e.g. addition/removal of
entities).
 Should not require changes to external schema or
rewrites of application programs.
 Physical Data Independence
 Refers to immunity of conceptual schema to changes in
the internal schema.
 Internal schema changes (e.g. using different file
organizations, storage structures/devices).
 Should not require change to conceptual or external
schemas.

Database Systems 11
Roles in the Database Environment
 Data Administrator (DA)
 Database Administrator (DBA)
 Database Designers (Logical and Physical)
 Application Programmers
 End Users (naive and sophisticated)

Database Systems 12
Database Languages
 Data Definition Language (DDL)
 Allows the DBA or user to describe and name
entities, attributes, and relationships required
for the application
 plus any associated integrity and security
constraints.

Database Systems 13
Database Languages
 Data Manipulation Language (DML)
 Provides basic data manipulation operations
on data held in the database.
 Procedural DML
 allows user to tell system exactly how to
manipulate data.
 Non-Procedural DML
 allows user to state what data is needed rather
than how it is to be retrieved.

Database Systems 14
Database Languages
 Fourth Generation Language (4GL)
 Query Languages
 Forms Generators
 Report Generators
 Graphics Generators
 Application Generators

Database Systems 15
Data Model
 Integrated collection of concepts for
describing data, relationships between data,
and constraints on the data in an organization.
 Data Model comprises:
 a structural part;
 a manipulative part;
 possibly a set of integrity rules.
 Purpose
 To represent data in an understandable way.

Database Systems 16
Data Models
 Categories of data models include:
 Object-based
 Record-based
 Physical.
 Object-Based Data Models
 Entity-Relationship
 Semantic
 Functional
 Object-Oriented.

Database Systems 17
Data Models
 Record-Based Data Models
 Relational Data Model
 Network Data Model
 Hierarchical Data Model.
 Physical Data Models

Database Systems 18
Conceptual Modelling
 Conceptual schema is the core of a system supporting
all user views.
 Should be complete and accurate representation of an
organization’s data requirements.
 Conceptual modeling is process of developing a
model of information use that is independent of
implementation details.
 Result is a conceptual data model.

Database Systems 19
Functions of a DBMS
 Data Storage, Retrieval, and Update.
 A User-Accessible Catalog.
 Transaction Support.
 Concurrency Control Services.
 Recovery Services.

Database Systems 20
Functions of a DBMS
 Authorization Services.
 Support for Data Communication.
 Integrity Services.
 Services to Promote Data Independence.
 Utility Services.

Database Systems 21
Components of a DBMS

Database Systems 22
Components of Database Manager (DM)

Database Systems 23
END OF CHAPTER 2

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