Systems Design

1. Application Architecture Systems Design

2. Chapter 9 Application Architecture Systems Analysis and Design Fourth Edition

3. Objectives • List the main issues that a systems analyst should consider when selecting application architecture, including enterprise resource planning, initial cost and TCO (total cost of ownership), scalability, Web integration, legacy requirements, security, and processing options • Describe servers, server-based processing, clients, and client-based processing Systems Analysis and Design Fourth Edition

4. Objectives • Explain client/server architecture, including the difference between fat and thin clients • Discuss client/server tiers, cost-benefit issues, and performance considerations • Explain the impact of the Internet on application architecture • Describe online and batch processing Systems Analysis and Design Fourth Edition

5. Objectives • Define network topology, and provide examples of hierarchical, bus, star, and ring network models • Explain network protocols and licensing issues • Describe tools for modeling application architecture Systems Analysis and Design Fourth Edition

6. Objectives • Explain system management tools and techniques, including performance management, system security, fault management, backup, and disaster recovery • Describe the systems design specification and explain the contents of each section Systems Analysis and Design Fourth Edition

7. Introduction • Application architecture translates the logical design into a physical structure that includes hardware, software, network support, and processing methods • The end product of the systems design phase is the preparation of the system design specification document Systems Analysis and Design Fourth Edition

8. Design Checklist • Enterprise resource planning • Initial cost and TCO • Scalability • Web integration • Legacy interface requirements • Security • Processing options Systems Analysis and Design Fourth Edition

9. Design Checklist • Enterprise resource planning (ERP) • Establishes an enterprisewide strategy for IT resources • Main advantage is that it describes a specific hardware and software environment • Can help companies achieve faster response, better customer service, and lower operating costs Systems Analysis and Design Fourth Edition

10. Design Checklist • Initial cost and TCO • Review cost estimates • Reanalyze system requirements and alternatives • Is the development choice still the best? • Any changes in application package? • New types of outsourcing? • Economic, government, regulatory changes? • Any technology changes? • Change in assumptions? • Merger or acquisition opportunities? • Marketplace trends? Systems Analysis and Design Fourth Edition

11. Design Checklist • Scalability • The measure of a system’s ability to change to meet the changing needs of a business enterprise • Especially important in implementing systems that are volume-related Systems Analysis and Design Fourth Edition

12. Design Checklist • Web integration • If a new application is part of an e-commerce strategy, it must have some degree of integration with other Web-based components • A Web-centricarchitecture follows Internet design protocols • A Web-centric application can run on the Internet or company Intranet Systems Analysis and Design Fourth Edition

13. Design Checklist • Legacy interface requirements • Legacy systems are older systems that typically run on mainframe computers • Should be determined how the new application will communicate with the existing legacy systems • Involves analysis of data formats and compatibility • Needs to be know if the new application will eventually replace the legacy system Systems Analysis and Design Fourth Edition

14. Design Checklist • Security • Determine how the company will address security issues • Web-based systems raise concerns about protecting critical data in the Internet environment • E-commerce applications raise concerns from customers that their credit card and personal data are safe and secure Systems Analysis and Design Fourth Edition

15. Design Checklist • Processing options • How the new application processes data affects the physical design • If system updates, file maintenance, or batch processing can be done at off-peak times, costs will be lower Systems Analysis and Design Fourth Edition

16. Planning the Architecture • Three main functions of an information system • Data storage and access methods • Application programs to hand the processing logic • An interface that allows users to interact with the system • These functions are performed on a server, on a client, or are divided between the server and the client Systems Analysis and Design Fourth Edition

17. Planning the Architecture • Servers • A computer that supplies data, processing services to one or more computers, called clients • Mainframe architecture is where the server performs all the processing • A server that supports a large number of clients at various locations is called a centralized system Systems Analysis and Design Fourth Edition

18. Planning the Architecture • Servers • Background • Mainframe architecture was the only system design available in the 1960s • Early systems performed all data input and output at a central location (data processing center) • Users had no input or output capability Systems Analysis and Design Fourth Edition

19. Planning the Architecture Systems Analysis and Design Fourth Edition

20. Planning the Architecture • Servers • Server-based processing • Terminals were installed at remote locations as network technology advanced • Main advantage is that various types of terminals can communicate with the mainframe • A disadvantage is that character-based terminals are used providing a limited interface for users Systems Analysis and Design Fourth Edition

21. Planning the Architecture • Clients • Stand-alone computing • The workstation performs all the functions of a server • Inefficient, expensive, and raises concerns about data security, integrity, and consistency Systems Analysis and Design Fourth Edition

22. Planning the Architecture • Clients • Local and wide area networks • Local area network (LAN) allows sharing of data and hardware resources • Wide area network (WAN) can link users who are continents apart • Distributed systems increase concerns about data security and integrity Systems Analysis and Design Fourth Edition

23. Planning the Architecture Systems Analysis and Design Fourth Edition

24. Planning the Architecture Systems Analysis and Design Fourth Edition

25. Planning the Architecture • Clients • Client-based processing • Clients share data stored on a local server • In a file server design, a LAN client has a copy of the application program, but not the data • A disadvantage is that character-based terminals are used providing a limited interface for users Systems Analysis and Design Fourth Edition

26. Planning the Architecture Systems Analysis and Design Fourth Edition

27. Client/Server Architecture • Overview • Refers to systems that divide processing between one or more networked clients and a central server • The client submits a request for information from the server, which carries out the operation and responds to the client • Early client/server systems did not produce expected cost savings • As large scale networks grew, client/server systems became more cost effective Systems Analysis and Design Fourth Edition

28. Client/Server Architecture Systems Analysis and Design Fourth Edition

29. Client/Server Architecture Systems Analysis and Design Fourth Edition

30. Client/Server Architecture • Client/Server design styles • Client/Server design depends on the type of server and the relationship between the server and the clients • The nature of the communication depends on the type of server • Database server • Transaction server • Object server • Web server Systems Analysis and Design Fourth Edition

31. Client/Server Architecture • Types of clients: fat and thin • A fat client (thick client) design locates all or most of the application processing logic at the client • A thin client design locates all or most of the processing logic at the server • Thin client designs provide better performance and has lower TCO • Fat client design is simpler and less expensive to develop Systems Analysis and Design Fourth Edition

32. Client/Server Architecture Systems Analysis and Design Fourth Edition

33. Client/Server Architecture • Client/Server tiers • Two-tier design • User interface resides on the client • All data resides on the server • Application logic can run on either • Three-tier design • User interface resides on the client • All data resides on the server • An application server processes the client requests and translates them into data access commands • Also called n-tier designs Systems Analysis and Design Fourth Edition

34. Client/Server Architecture Systems Analysis and Design Fourth Edition

35. Client/Server Architecture • Client/Server tiers • Three-tier design • Enhances overall performance by reducing the server’s workload • Relieves clients of complex processing tasks Systems Analysis and Design Fourth Edition

36. Client/Server Architecture Systems Analysis and Design Fourth Edition

37. Client/Server Architecture • Middleware • Software that connects dissimilar applications and enables them to communicate and exchange data Systems Analysis and Design Fourth Edition

38. Client/Server Architecture • Cost-Benefit issues • Enable companies to scale the system in a rapidly changing environment • Allows companies to transfer applications from expensive mainframes to less expensive client platforms • Reduce network load and improve response times so users have faster access to data Systems Analysis and Design Fourth Edition

39. Client/Server Architecture • Client/Server performance issues • When the number of clients and the demand for services increases beyond a certain point, client requests go into a queue, and system performance declines dramatically • Client/Server systems must be designed so the client contacts the server only when necessary • Data can be stored in more than one location using a distributed database management system (DDBMS) Systems Analysis and Design Fourth Edition

40. Impact of the Internet • E-Commerce strategies • In-house development • In-house solutions usually require a greater initial investment, but provide more flexibility • Company has more freedom to integrate with customers and suppliers Systems Analysis and Design Fourth Edition

41. Impact of the Internet Systems Analysis and Design Fourth Edition

42. Impact of the Internet • E-Commerce strategies • Packaged solutions and e-commerce service providers • Many vendors offer turnkey systems for companies that want to get an e-business up and running quickly • An ASP provides applications by charging a usage or subscription fee • Must consider whether the lower initial cost outweigh the disadvantage of reduced flexibility later on Systems Analysis and Design Fourth Edition

43. Impact of the Internet • E-Commerce strategies • Corporate portals • Provides access for customers, employees, suppliers, and the public • Poor design can weaken system effectiveness and value Systems Analysis and Design Fourth Edition

44. Impact of the Internet • Industry experience and trends • Consider the experience of other companies in the same industry when constructing Internet- or intranet-based systems • Firms such as IBM and Microsoft offer numerous case studies and examples of successful development Systems Analysis and Design Fourth Edition

45. Processing Methods • Online versus batch processing • Four characteristics of online processing • The system processes transactions completely when 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 Systems Analysis and Design Fourth Edition

46. Processing Methods • Batch processing • Data is collected and processed in groups (batches) • Typical method for large amounts of data that are processed periodically, such as paychecks • Batch processing can take place at off-peak times Systems Analysis and Design Fourth Edition

47. Processing Methods • Combined online and batch processing • A retail chain is a typical example of online transaction processing and batch processing of accounting data Systems Analysis and Design Fourth Edition

48. Network Models • A network allows hardware, software, and data resources to be shared • Network topology • The way a network is configured • Four topologies • Hierarchical • Bus • Star • Ring Systems Analysis and Design Fourth Edition

49. Network Models • Network topology • Hierarchical network • One computer (typically a mainframe) controls the entire network • Satellite processors control lower levels of processors and devices Systems Analysis and Design Fourth Edition

50. Network Models • Network topology • Bus network • A single communication path connects all computers and devices • Information is transmitted in either direction • Devices can be attached or detached at any point without affecting the rest of network Systems Analysis and Design Fourth Edition