Transcript Chapter 8
Systems Analysis & Design
(Sixth Edition)
PHASE 3: SYSTEMS DESIGN
Chapter 8
System Architecture
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Chapter Objectives
Provide a checklist of issues to consider when
selecting a system architecture
Describe servers, server-based processing, clients,
and client-based processing
Explain client/server architecture, including tiers, costbenefit issues, and performance considerations
Describe the impact of the Internet on system
architecture
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Chapter Objectives
Explain the difference between online and
batch processing
Define network topology, and provide
examples of hierarchical, star, bus, and ring
network models
Explain network protocols and licensing issues
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Chapter Objectives
Explain system management tools and
techniques, including performance
measurement, fault management, backup, and
disaster recovery
Describe the systems design specification and
explain the contents of each section
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Introduction
An effective system combines elements into
an architecture, or design, that is flexible, costeffective, technically sound, and able to
support the information needs of the business
System architecture translates the logical
design of an information system into a physical
structure that includes hardware, software,
network support, processing methods, and
security
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System Architecture Checklist
A systems analyst must approach system
architecture with an overall checklist
Enterprise resource planning (ERP)
Initial and total cost of ownership (TCO)
Scalability
Web integration
Legacy system interface requirements
System security
Processing options
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System Architecture Checklist
Enterprise Resource Planning (ERP)
The objective of ERP is to establish a company-wide
strategy for using IT resources
Describes environment – platform
Supply chain management
Initial Cost and TCO
During the final design stage, you make decisions
that will have a major impact on the initial costs and
TCO for the new system
You should review all previous cost estimates
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System Architecture Checklist
Initial Cost and TCO
Ask questions like the following
Is in-house development still best choice?
Is specific package still best choice?
New outsourcing available?
New technology available?
Answers might affect the initial cost and TCO for the
proposed system
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System Architecture Checklist
Scalability
Scalability, also called extensibility
Especially important in implementing systems that
are volume-related, such as transaction processing
systems
Web Integration
An information system includes application
programs, also called applications
Web-centric
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System Architecture Checklist
Legacy System Interface Requirements
The new system might have to interface with one or more
legacy systems
Interfacing a new system with legacy systems involves
analysis of data formats and compatibility
The analyst must know if the new application eventually will
replace the legacy system
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System Architecture Checklist
Processing Options
Online or Batch
24/7
Backup and Recovery
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System Architecture Checklist
Security Issues
Security is a concern at every stage of system
development
The systems analyst must consider security issues
that relate to system design specifications and
determine how the company will address them
Web-based systems introduce additional security
concerns
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Planning the Architecture
Every information system involves 3 main functions:
Data Storage and Access Methods
Application Programs
Interface
The 3 functions may be performed on a …
Server
OR
Client
OR
Divided between Server and Client
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Client/Server Architecture
Today’s interconnected world requires an
information architecture that spans the entire
enterprise
Whether you are dealing with a departmental
network or a multinational corporation, as a
systems analyst you will work with a
distributed computing strategy called
client/server architecture
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Client/Server Architecture
Overview
Client/server architecture
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Client/Server Architecture
Client/Server Design Styles
Many forms
Database Server
Transaction Server
Web Server
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Client/Server Architecture
Types of Clients: Fat and Thin
Fat client - Thick client
Thin client
Comparison:
Thin better performance
Thick more processing
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Client/Server Architecture
Client/Server Tiers
Two-tier design
Three-tier design
Middle layer
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Client/Server Architecture
Middleware -Cost-Benefit Issues
Scale the system
http://www.centene.com/investors/annual_reports
Transfer applications
Improve response times
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Client/Server Architecture
Client/Server Performance Issues
Separation of server-based data and networked clients
Separates applications and data
Client contacts server only when necessary
Distributed Database Management System (DDBMS)
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Internet-Based Architecture
The Internet has had an enormous impact on
system architecture
To support this trend, systems analysts must
suggest e-commerce strategies that apply
available technology and meet their
company’s business requirements
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Internet-Based Architecture
Developing E-Commerce Solutions In-House
If you decide to proceed with an in-house solution,
you must have an overall plan to help achieve your
goals
An in-house solution usually requires a greater initial
investment, but provides more flexibility for a
company that must adapt quickly in a dynamic ecommerce environment
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Internet-Based Architecture
Packaged Solutions and E-Commerce
Service Providers
Turnkey systems
Application service provider (ASP)
Does lower initial cost outweigh disadvantage of
reduced flexibility?
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Internet-Based Architecture
Corporate Portals
A portal is an entrance to a multifunction Web site
A corporate portal can provide access for customers,
employees, suppliers, and the public
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Network Models
The OSI Reference Model – consists of 7 layers
Application layer
Presentation layer
Session layer
Transport layer
Network layer
Data link layer
Physical layer
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Network Models
Network Topology
Hierarchical network
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Network Models
Network Topology
Star network
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Network Models
Network Topology
Bus network
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Network Models
Network Topology
Ring network
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Network Models
Network Topology
Other topologies
http://compnetworking.about.com/od/networkdesign/a/topologies.htm
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Network Models
Network Protocols and Licensing Issues
The network must use a protocol
A popular network protocol is Transmission
Control Protocol/Internet Protocol (TCP/IP)
A familiar example of a TCP/IP protocol is the
file transfer protocol (FTP)
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Systems Design Completion
System Design Specification
Baseline
Contents vary depending on company
standards
You do not have to turn this in
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Systems Design Completion
User Approval of …
Interface design
Report and menu designs
Data entry screens
Source documents
Other
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Systems Design Completion
Presentations
Systems analysts, programmers, technical staff
Department managers and users
Company management
Objective: Obtain management’s approval/support
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Chapter Summary
The analyst must consider enterprise resource planning, initial
cost and TCO, scalability, Web integration, legacy interface
requirements, security, and processing options
System security is an important concern
An architecture requires servers and clients
Compared to file server designs, client/server systems are more
scalable and flexible
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Chapter Summary
Networks allow the sharing of hardware, software, and data
resources in order to reduce expenses and provide more
capability to users
The way a network is configured is called the network topology
The system design specification presents the complete
systems design for an information system
Any questions?
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