week05 - database design
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Database I
Background
Database Design
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Overview of the IS Life Cycle
Information System enable the collection,
management, control of information with in
the organization A computer based IS includes the following
components:
Database
Database Software
Application Software
Computer Hardware
Personal developing and using the system
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Overview of the IS Life Cycle
(Cont.)
Database is fundamental component of IS
Its development/usage should be viewed
from perspective of the wider requirements ofthe organization
Therefore, we will look here at the database
development life cycle
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Database System
Development Lifecycle
Database Planning
System Definition
Requirement Collection and
Analysis
Prototyping
DBMS Selection
Application Design
Implementation
Testing
Maintenance
Conceptual Design
Logical Design
Physical Design
Database Design
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Database Planning
Management activities that allow stages of
database system development lifecycle to be
realized as efficiently and effectively aspossible
Database planning should also include
development of standards that govern:
how data will be collected,
how the format should be specified,
what necessary documentation will be needed,
how design and implementation should proceed
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System Definition
Describes scope and boundaries of database
system and the major user views
User view defines what is required of adatabase system from perspective of:
a particular job role (such as Manager or
Supervisor) or
enterprise application area (such as marketing,personnel, or stock control)
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Requirements Collection and
Analysis
Process of collecting and analyzinginformation about the part of organization tobe supported by the database system, and
using this information to identify usersrequirements of new system
Information is gathered for each major userview including: a description of data used or generated;
details of how data is to be used/generated;
any additional requirements for new databasesystem
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Database Design
Process of creating a design for a databasethat will support the enterprises missionstatement and mission objectives for the
required database system Main purposes of data modeling include:
to assist in understanding the meaning(semantics) of the data;
to facilitate communication about the informationrequirements
Building data model requires answeringquestions about entities, relationships, andattributes
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Database Design (Cont.)
Three phases of database design:
Conceptual database design
Logical database design Physical database design
Conceptual database design
Process of constructing a model of the data used in an
enterprise, independent ofallphysical considerations Data model is built using the information in users
requirements specification
Conceptual data model is source of information for
logical design phase
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Database Design (Cont.)
Logical Database Design
Process of constructing a model of the data used in an
enterprise based on a specific data model (e.g. relational),
but independent of a particular DBMS and other physicalconsiderations
Conceptual data model is refined and mapped on to a
logical data model
Physical Database Design
Process of producing a description of the databaseimplementation on secondary storage
Describes base relations, file organizations, and indexes
used to achieve efficient access to data. Also describes any
associated integrity constraints and security measures
Developed according to specific DBMS in mind
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Database Design (Cont.)
Three-Level ANSI-SPARC Architecture and
Phases of Database Design
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DBMS Selection
Selection of an appropriate DBMS to support
the database system.
Undertaken at any time prior to logical designprovided sufficient information is available
regarding system requirements
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Application Design
Design of user interface and application programs
that use and process the database
Database design and application design are
parallel activities
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Prototyping
Building working model of a database system
Purpose
to identify features of a system that work well, orare inadequate;
to suggest improvements or even new features;
to clarify the users requirements;
to evaluate feasibility of a particular systemdesign
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Implementation
Physical realization of the database and
application designs
Use DDL to create database schemas andempty database files
Use DDL to create any specified user views
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Data Conversion and Loading
Transferring any existing data into new
database and converting any existing
applications to run on new database Only required when new database system is
replacing an old system
DBMS normally has utility that loads existing
files into new database
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Testing
Process of running the database system with
intent of finding errors
Use carefully planned test strategies andrealistic data
Examples of criteria include:
Learnability;
Performance;
Robustness;
Recoverability;
Adaptability
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Operational Maintenance
Process of monitoring and maintainingdatabase system following installation
Monitoring performance of system. if performance falls, may require tuning or
reorganization of the database
Maintaining and upgrading databaseapplication (when required)
Incorporating new requirements intodatabase application
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