Systems%20Analysis%20and%20Design%209th%20Edition

1
Systems Analysis and Design 9th Edition

• Chapter 10
• System Architecture

2
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
• Compare in-house e-commerce development with
  packaged solutions

3
Chapter Objectives

• Discuss the potential impact of cloud computing
  and Web 2.0
• Explain the difference between online and batch
  processing
• Define network topology, including hierarchical,
  bus, ring, and star models

4
Chapter Objectives

• Explain network protocols and licensing issues
• Describe wireless networking, including wireless
  standards, topologies, and trends
• Describe the system design specification

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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, and processing methods

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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
• Supply chain management (SCM)
• 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

• Scalability
• Scalability, also called extensibility, refers to
  a systems ability to expand, change or downsize
  easily to meet the changing need of a business
  enterprise
• Especially important in implementing systems that
  are volume-rated, such as transaction processing
  systems

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System Architecture Checklist

• Web Integration
• An information system includes applications
• Web-centric architecture
• Avoids many of the connectivity and compatibility
  problems that typically arise
• E-marketplaces

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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 a legacy system
  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
• In planning the architecture, designers also must
  consider how the system will process data -
  online or in batches
• Provision must be made for backup and speedy
  recovery in the event of system failure

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System Architecture Checklist

• Security Issues
• Security threats and defenses are a major concern
  to a systems analyst
• The analyst must consider security issues that
  relate to system design specifications
• Web-based systems introduce additional security
  concerns

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Planning the Architecture

• Servers
• Server
• Clients
• Mainframe architecture
• Server-based processing

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Planning the Architecture

• Clients
• As PC technology exploded in the mid-1980s and
  1990s, powerful microcomputers quickly appeared
  on corporate desktops
• Users found that they could run their own word
  processing, spreadsheet, and database
  applications
• Companies linked the stand-alone computers into
  networks

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Planning the Architecture

• Clients
• Stand-Alone Computing
• Local and wide area networks
• Client-based processing

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Client/Server Architecture

• Overview

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Client/Server Architecture

• Client/Server Design Styles

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Client/Server Architecture

• Fat and Thin Clients

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Client/Server Architecture

• Client/Server Tiers
• Two-tier design
• Three-tier design
• Middleware
• Enables the tiers to communicate and pass data
  back and forth
• Provides a transparent interface
• Can integrate legacy systems and Web-based
  applications

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Client/Server Architecture

• Cost-Benefit Issues
• Client/server systems enable the firm to scale
  the system in a rapidly changing environment
• Client/server computing also allows companies to
  transfer applications from expensive mainframes
  to less expensive client platforms
• Client/server systems reduce network load and
  improve response times

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Client/Server Architecture

• Client/Server Performance Issues
• In contrast to the centralized system, a
  client/server design separates applications and
  data
• Distributed database management system (DDBMS)
• The system is scalable, so new data sites can be
  added without reworking the system design
• The system is less likely to experience
  catastrophic failure

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Internet-Based Architecture

• Developing E-Commerce Solutions In-House

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Internet-Based Architecture

• Packaged Solutions and E-commerce Service
  Providers
• Many vendors offer turnkey systems for companies
• Another alternative is to use an application
  service provider (ASP)
• Another option is managed hosting
• Consider the experience of other companies in the
  same industry

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Internet-Based Architecture

• Corporate Portals
• A corporate portal can provide access for
  customers, employees, suppliers, and the public
• Cloud Computing
• Effectively eliminates compatibility issues
• Scaling on demand
• Requires significantly more bandwidth

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Internet-Based Architecture

• Web 2.0
• Envisions a second generation of the web that
  will enable people to collaborate, interact, and
  share information more dynamically
• Wiki
• Internet operating system

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Processing Methods

• Online Processing
• Because it is interactive, online processing
  avoids delays and allows a constant dialog
  between the user and the system
• Online processing also can be used with
  file-oriented systems

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Processing Methods

• Batch Processing
• The IT operations group can run batch programs on
  a predetermined schedule, without user
  involvement, during regular business hours, at
  night, or on weekends
• Require significantly fewer network resources
  than online systems

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Processing Methods

• Combined Online and Batch Processing

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Network Models

• The OSI Reference Model
• The OSI model consists of seven layers
• Each layer performs a specific function
• Offers a set of design standards

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Network Models

• Network Protocols
• In all cases, the network must use a protocol
• Transmission Control Protocol/Internet Protocol
  (TCP/IP)
• File Transfer Protocol (FTP)

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Network Models

• Network Topology
• Hierarchical network
• it mirrors the actual operational flow in the
  organization
• One disadvantage of a hierarchical network is
  that if a business adds additional processing
  levels, the network becomes more complex and
  expensive to operate and maintain

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Network Models

• Network Topology
• Bus network
• Devices can be attached or detached from the
  network at any point without disturbing the rest
  of the network
• Overall performance declines as more users and
  devices are added
• Today, the bus design is much less popular

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Network Models

• Network Topology
• Ring network
• One disadvantage of a ring network is that if a
  network device fails (such as a PC or a server),
  the devices downstream from the failed device
  cannot communicate with the network
• Multistation Access Unit (MAU)

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Network Models

• Network Topology
• Star network
• Disadvantage of the star design is that the
  entire network is dependent on the switch
• However, in most large star networks, backup
  switches are available immediately in case of
  hardware failure

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Network Models

• Network Topology
• Mesh network
• While this design is extremely reliable, it also
  is very expensive to install and maintain
• Originally developed for military applications

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Network Models

• Routers
• Routers differ from switches in that they work at
  a higher OSI level
• Can connect to a larger, dissimilar network, such
  as the Internet
• Gateway
• Proxy server

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Network Models

• Network Modeling Tools
• As you translate the OSI logical model into a
  physical model of the networked system, you can
  use software tools
• Network Licensing Issues
• Software licensing restrictions

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Wireless Networks

• A wireless local area network, or WLAN
• Wireless Network Standards
• 802.11
• Institute of Electrical and Electronics Engineers
  (IEEE)
• Amendments
• Mbps (megabits per second)

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Wireless Networks

• Wireless Network Standards
• 802.11g
• 802.11n
• Multiple input/multiple output (MIMO)
• Multipath design
• 802.11y

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Wireless Networks

• Wireless Network Topologies
• Basic Service Set (BSS) infrastructure mode
• Access point
• Extended Service Set (ESS)
• Roaming
• Independence Service Set (ISS) peer-to-peer mode

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Wireless Networks

• Wireless Trends
• Wi-Fi Alliance
• Wi-Fi (wireless fidelity)
• BlueTooth
• On addition to 802.11 protocols for LANs, IEEE is
  working on 802.16 standards
• MANs (metropolitan area networks)
• WiMAX

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Systems Design Completion

• System Design Specification
• A typical system design specification uses a
  structure similar to the following
• Management summary
• System components
• System environment
• Implementation requirements
• Time and cost estimates
• Additional material

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Systems Design Completion

• User Approval
• Users must review and approve the interface
  design, report and menu designs, data entry
  screens, source documents, and other areas of the
  system that affect them
• Other IT department members also need to review
  the system design specification
• When the system design specification is complete,
  you distribute the document to a target group of
  users, IT department personnel, and company
  management

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Systems Design Completion

• Presentations
• The first presentation is to the systems
  analysts, programmers, and technical support
  staff members
• Your next presentation is to department managers
  and users from departments affected by the system
• The final presentation is for company management
• Management might reach one of three decisions
  proceed with systems development, perform
  additional work on the systems design phase, or
  terminate the project

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Chapter Summary

• An information system combines hardware,
  software, data, procedures, and people into a
  system architecture
• The analyst must consider enterprise resource
  planning, initial cost and TCO, scalability, Web
  integration, legacy interface requirements,
  processing options, and security issues
• An architecture requires servers and clients

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Chapter Summary

• Compared to file server designs, client/server
  systems are more scalable and flexible
• In implementing a design, an analyst should
  consider e-commerce strategies, the availability
  of packaged solutions, and corporate portals,
  which are entrances to a multifunction Web site
• The primary processing methods are online and
  batch processing

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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
• Chapter 10 complete