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Systems Analysis & Design(Sixth Edition)

Chapter 8System Architecture

PHASE 3: SYSTEMS DESIGN

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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, cost-benefit 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, cost-effective, 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 performanceThick 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 e-commerce 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?