1. CHAPTER 10 SYSTEM CONSTRUCTION PLANNING 1

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 2

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 Explain network protocols and licensing issues Describe wireless networking, including wireless standards, topologies, and trends Describe the system design specification 3

4. 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 4

5. System Architecture Checklist Before making a decision, the analyst must consider seven specific issues that will affect the architecture choice: 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 5

6. 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 Web Integration ▫An information system includes applications ▫Web-centric architecture ▫Avoids many of the connectivity and compatibility problems that typically arise ▫E-marketplaces 6

7. 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 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 7

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 8

9. Planning the Architecture Main function of IS: data storage and access, application program to handle processing and interface. Three main function of IS are performed on a server or client. ▫Servers  Computer that supplies data,processing services or other support to one or more computers, called client  Mainframe architecture  Server-based processing 9

10. In centralized design, the remote user’s keystrokes are transmitted to the mainframe, which responds by sending screen output back to the user’s screen 10

11. 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

12. Planning the Architecture Clients ▫Stand-Alone Computing-the workstation performs all the functions of a server by storing, accessing and processing data as well as providing user interface. ▫Local and wide area networks- ▫Client-based processing 12

13. A WAN can connect many LANs and link users who are continents apart 13

14. Client/Server Architecture System that divide processing between one or more networked clients and a central server. In typical client server system: ▫The client handles the entire user interface ▫The server stores the data and provides data access and database management functions 14

15. Comparisons of the characteristics of clients/server and mainframe systems. CharacteristicClient/serverMainframe Basic architectureVery flexibleVery rigid Application development Flexible Fast Object oriented Highly structured Slow Traditional User environmentPC based GUI Empower the user Improves productivity Uses terminals Text interface Constrains the user Limited options Security and control features Decentralized Difficult to control Centralized Easier to control Processing optionsCan be shared and configured in any form desired Cannot be modified Data storage optionsCan be distributed to place data closer to users All data is stored centrally H/w,s/w integrationVery flexible Multivendor model Very rigid Single proprietary vendor 15

16. A file server design compared to a client/server design 16

17. Client/Server Architecture Client/Server Design Styles 17

18. Client/Server Architecture Fat and Thin Clients 18

19. 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 19

20. Characteristics of two tier versus three tier client/server design 20 DataApplication LogicUser Interface ServerClient Data Server Application Server Client Two tier Three tier

21. 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 21

22. 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 22

23. Internet-Based Architecture Developing E-Commerce Solutions In-House 23

24. 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 24

25. 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 25

26. 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 26

27. 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 ▫Online processing have four typical characteristics:  The system process transactions completely when and where they occur.  Users interact directly with the information system  Users can access data randomly  The information system must be available whenever necessary to support business functions. 27

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29. 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 29

30. Processing Methods Combined Online and Batch Processing 30

31. 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 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) 31

32. Network Models Network Topology ▫The Way Network configured ▫Hierarchical network  One or more powerful servers control the entire 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 32

33. A hierarchical network with a single server that controls the network 33

34. 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 34

35. 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) 35

36. 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 36

37. Network Models Mesh Network ▫Each node connects to every other node ▫Expensive to install and maintain 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 –provides Internet connectivity for internal LAN users 37

38. 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, such as Microsoft Visio Network Licensing Issues – When considering a network design, it is important to take into account software licensing restrictions 38

39. Wireless Networks A wireless local area network, or WLAN Wireless Network Standards ▫802.11 developed by Institute of Electrical and Electronics Engineers (IEEE) ▫Several Amendments were intended to improve bandwidth, range and security ▫Maximum speed is measured in Mbps (megabits per second) 39

40. Wireless Networks Wireless Network Standards 40

41. Wireless Networks Wireless Network Topologies ▫Three major network topologies:  Basic Service Set (BSS) – infrastructure mode  Extended Service Set (ESS)  Independence Service Set (ISS) – peer-to-peer mode 41

42. 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) ▫WirelessMAN™ - WiMAX 42

43. Systems Design Completion System Design Specification ▫Document that presents the complete design for the new information system ▫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 43

44. 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 44

45. 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 45

46. 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 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 46

47. Chapter Summary The primary processing methods are online and batch processing 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 47

48. Review Questions 1.When selecting an architecture, what items should a system analyst consider as part of the overall design checklist? 2.Describe client/server architecture, including fat and thin clients, client/server tiers and middleware. 3.Explain the difference between online processing and batch processing. 4.What is topology. 5.Explain about bus, star, ring and mesh topology. 6.Explain 3 types of wireless network topology. 48