1. Systems Analysis and Design 8th Edition
Chapter 10
System Architecture

2. 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

3. 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)
Faster response, better customer service, and lower costs
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

4. 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

5. 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

6. 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

7. 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

8. 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

9. Planning the Architecture
Servers
Server
Clients
Mainframe architecture
Server-based processing

10. 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

11. Planning the Architecture
Clients
Stand-Alone Computing
Local and wide area networks
Client-based processing

12. Client/Server Architecture
Overview

13. Client/Server Architecture
Client/Server Design Styles

14. Client/Server Architecture
Fat and Thin Clients

15. Client/Server Architecture
Client/Server Tiers (page 458)
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

16. 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

17. 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

18. Internet-Based Architecture
Developing E-Commerce Solutions In-House

19. 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

20. 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
Availability
Security

21. 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 – Collective knowledge
Internet operating system, sharing resources

22. 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

23. 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

24. Processing Methods
Combined Online and Batch Processing

25. Network Models The OSI Reference Model (page 471)
The OSI model consists of seven conceptual layers
Each layer performs a specific function
Offers a set of design standards
Network Modeling Tools
As you translate the OSI logical model into a physical model of the networked system, you can use software tools, such as Microsoft Visio

26. 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

27. 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

28. 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)
Manages data flow between connected devicesw

29. 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

30. Network Models Routers
Routers differ from switches in that they work at OSI level 3 (IP packets)
Can connect to a larger, dissimilar network, such as the Internet (Gateway)
Proxy server
Connects internal LAN clients to Internet

31. Network Models Network Protocols Network 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)
Network Licensing Issues
When considering a network design, it is important to take into account software licensing restrictions

32. Wireless Networks A wireless local area network, or WLAN
Wireless Network Standards
802.11
Institute of Electrical and Electronics Engineers (IEEE)
Versions or amendments to improve bandwidth, range and security
Mbps (megabits per second)

33. Wireless Networks
Wireless Network Standards

34. Wireless Networks Wireless Network Topologies (pgs. 477-478)
Basic Service Set (BSS) – infrastructure mode
Access point
Extended Service Set (ESS)
Roaming
Independence Service Set (ISS) – peer-to-peer mode

35. Wireless Networks Wireless Trends Wi-Fi Alliance
Wi-Fi (wireless fidelity)
BlueTooth (close acces, low power)
On addition to protocols for LANs, IEEE is working on standards (30 mile range) called:
MANs (metropolitan area networks)
WirelessMAN™ - WiMAX

36. Systems Design Completion
System Design Specification
A typical system design specification uses a structure similar to the following:
Executive summary
System components
System environment
Implementation requirements
Time and cost estimates
Appendices

37. 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

38. 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