Systems Analysis and Design 8 th Edition

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 • 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 802.11 protocols for LANs, IEEE is working on 802.16 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