Post on 25-Dec-2015
transcript
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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?