This chapter discusses system architecture and design. It covers selecting an architecture, client/server models, online and batch processing, network topologies, wireless networks, and completing the system design specification. The objectives are to understand issues in selecting an architecture, describe different processing and network designs, and explain how to finalize a system design.

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
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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
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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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5. 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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6. 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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7. System Architecture Checklist
• Scalability
– Scalability, also called extensibility, refers to a
system’s 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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8. 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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9. 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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10. 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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11. 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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12. Planning the Architecture
• Servers
– Server
– Clients
– Mainframe architecture
– Server-based processing
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13. 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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14. Planning the Architecture
• Clients
– Stand-Alone Computing
– Local and wide area
networks
– Client-based processing
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15. Client/Server Architecture
• Overview
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16. Client/Server Architecture
• Client/Server Design Styles
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17. Client/Server Architecture
• Fat and Thin Clients
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18. 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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19. 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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20. 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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21. Internet-Based Architecture
• Developing E-Commerce Solutions In-House
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22. 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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23. 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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24. 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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25. 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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26. 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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27. Processing Methods
• Combined Online and Batch Processing
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28. 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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29. 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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30. 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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31. 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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32. 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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33. 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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34. 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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35. 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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36. 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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37. 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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38. Wireless Networks
• Wireless Network Standards
– 802.11g
– 802.11n
– Multiple input/multiple output (MIMO)
– Multipath design
– 802.11y
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39. 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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40. 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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41. Systems Design Completion
• System Design Specification
– A typical system design specification uses a
structure similar to the following:
1. Management summary
2. System components
3. System environment
4. Implementation requirements
5. Time and cost estimates
6. Additional material
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42. 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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43. 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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44. 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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45. 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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46. 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
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