1. 9 Systems Analysis and Design in a Changing World, Fourth Edition

2. 9 Systems Analysis and Design in a Changing World, 4th Edition 2 Learning Objectives u Discuss the issues related to managing and coordinating the design phase of the SDLC u Explain the major components and levels of design u Describe each design phase activity u Describe common deployment environments and matching application architectures u Develop a simple network diagram and estimate communication capacity requirements

3. 9 Systems Analysis and Design in a Changing World, 4th Edition 3 Overview u This chapter l Completes the transition from analysis to design l Discusses issues related to design of new system l Describes all design phase activities l Describes network and architecture design u Analysis focuses on what system should do— business requirements u Design is oriented toward how system will be built —defining structural components

4. 9 Systems Analysis and Design in a Changing World, 4th Edition 4 Components Requiring Systems Design

5. 9 Systems Analysis and Design in a Changing World, 4th Edition 5 Analysis Objectives to Design Objectives

6. 9 Systems Analysis and Design in a Changing World, 4th Edition 6 Moving from Analysis to Design u Design l Converts functional models from analysis into models that represent the solution l Focused on technical issues l Requires less user involvement than analysis

7. 9 Systems Analysis and Design in a Changing World, 4th Edition 7 SDLC Phases with Design Phase Activities

8. 9 Systems Analysis and Design in a Changing World, 4th Edition 8 Design Phase Activities and Key Questions (Figure 9-5)

9. 9 Systems Analysis and Design in a Changing World, 4th Edition 9 Design and Integrate the Network u Network specialists establish network based on strategic plan u Project team typically integrates system into existing network u Technical requirements have to do with communication via networks u Technical issues handled by network specialists l Reliability, security, throughput, synchronization

10. 9 Systems Analysis and Design in a Changing World, 4th Edition 10 Design the Application Architecture u Specify how system use cases are carried out u Described during system analysis as logical models of system activities u After design alternative is selected, detailed computer processing is designed as physical models, such as physical data flow diagrams and structure charts (traditional) or interaction diagrams and class diagrams (OO) u Approach varies depending on development and deployment environments

11. 9 Systems Analysis and Design in a Changing World, 4th Edition 11 Design the User Interfaces u User interface quality is critical aspect of system u Design of user interface defines how user interacts with system l GUI – windows, dialog boxes, mouse interaction l Sound, video, voice commands u To user of system, user interface is the system u User interface specialists – interface designers, usability consultants, human factors engineers

12. 9 Systems Analysis and Design in a Changing World, 4th Edition 12 Design the System Interfaces u System interfaces enable systems to share and exchange information l Internal organization systems l Interfaces with systems outside organization l New system interfaces with package application that organization has purchased and installed u System interfaces can be complex u Organization needs very specialized technical skills to work on these interfaces

13. 9 Systems Analysis and Design in a Changing World, 4th Edition 13 Design and Integrate the Database u System analysis data model used to create physical database model u Collection of traditional computer files, relational databases, and/or object-oriented databases u Technical requirements, such as response times, determine database performance needs u Design work might involve l Performance tuning l Integration between new and existing databases

14. 9 Systems Analysis and Design in a Changing World, 4th Edition 14 Prototype for Design Details u Continue to create and evaluate prototypes during design phase u Prototypes confirm design choices l Database l Network architecture l Controls l Programming environment u Rapid application development (RAD) design prototypes evolve into finished system

15. 9 Systems Analysis and Design in a Changing World, 4th Edition 15 Design and Integrate the System Controls u Final design activity to ensure system has adequate safeguards (system controls) to protect organizational assets u Controls are needed for all other design activities l User interface – limit access to authorized users l System interface – protect from other systems l Application architecture – record transactions l Database – protect from software/hardware failure l Network design – protect communications

16. 9 Systems Analysis and Design in a Changing World, 4th Edition 16 Deployment Environment u Deployment environment definition bridges analysis and design l Hardware l System software l Networking u Common deployment environments in which system will operate u Related design patterns and architectures for application software

17. 9 Systems Analysis and Design in a Changing World, 4th Edition 17 Single-Computer and Multitier Architecture u Single-computer architecture l Mainframe-based l Limited by single machine capacity u Clustered and multi-computer architecture l Group of computers to provide processing and data storage capacity l Cluster acts as a single system l Multicomputer hardware/OS can be less similar than clustered

18. 9 Systems Analysis and Design in a Changing World, 4th Edition 18 Single-, Clustered, and Multicomputer Architectures

19. 9 Systems Analysis and Design in a Changing World, 4th Edition 19 Centralized Architecture u Deployment of all computer systems in a single location. l Common in banking, insurance, and catalog sales

20. 9 Systems Analysis and Design in a Changing World, 4th Edition 20 Distributed Architecture u Distributes system across several computers and locations u Relies on communication networks for geographic connectivity u Client/server architecture dominant model for distributed computing

21. 9 Systems Analysis and Design in a Changing World, 4th Edition 21 Computer Network u Set of transmission lines, specialized hardware, and communication protocols u Enables communication among different users and computer systems u Local area network (LAN) less than one kilometer long – connects computers within single building u Wide area network (WAN) over one kilometer long – implies much greater, global, distances u Router – directs information within network

22. 9 Systems Analysis and Design in a Changing World, 4th Edition 22 The Internet, Intranets, and Extranets u Internet – global collection of networks that use TCP/IP networking protocols u Intranets l Private networks using same TCP/IP protocols as the Internet l Limited to internal users u Extranets l Intranets that have been extended outside the organization

23. 9 Systems Analysis and Design in a Changing World, 4th Edition 23 Application Architecture u Complex hardware/networks require more complex software architectures u There are commonly used approaches (patterns) for application architecture l Client/server architecture l Three-layer client/server architecture l Web services architecture l Internet and Web-based application architecture

24. 9 Systems Analysis and Design in a Changing World, 4th Edition 24 Client/Server Architecture u Client/server divides programs into two types u Server – manages information system resources or provides well-defined services for client u Client – communicates with server to request resources or services u Advantage – deployment flexibility l Location, scalability, maintainability u Disadvantage – complexity l Performance, security, and reliability

25. 9 Systems Analysis and Design in a Changing World, 4th Edition 25 Interaction Among Multiple Clients and a Single Server (Figure 9-11)

26. 9 Systems Analysis and Design in a Changing World, 4th Edition 26 Client/Server Architectural Process u Decompose application into client and server programs, modules, or objects l Identify resources or services that can be centrally managed by independent software units u Determine which clients and servers will execute on which computer systems u Describe communication protocols and networks that connect clients and servers

27. 9 Systems Analysis and Design in a Changing World, 4th Edition 27 Internet and Web-Based Application Architecture u Web is complex example of client/server architecture u Can use Web protocols and browsers as application interfaces u Benefits l Accessibility l Low-cost communication l Widely implemented standards

28. 9 Systems Analysis and Design in a Changing World, 4th Edition 28 Negative Aspects of Internet Application Delivery u Breaches of security u Fluctuating reliability of network throughput u Throughput can be limited u Volatile, changing standards

29. 9 Systems Analysis and Design in a Changing World, 4th Edition 29 Network Design u Integrate network needs of new system into existing network infrastructure u Describe processing activity and network connectivity at each system location u Describe communications protocols and middleware that connects layers u Ensure that network capacity is sufficient l Data size per access type and average l Peak number of access per minute or hour

30. 9 Systems Analysis and Design in a Changing World, 4th Edition 30 Summary u Systems design is process of organizing and structuring components of system to allow construction (programming) of new system u Design phase of project consists of activities that relate to design of components of new system l Application architecture, user interfaces, system interfaces, databases, network diagrams, system controls l Prototyping may be required to specify any part or all of the design

31. 9 Systems Analysis and Design in a Changing World, 4th Edition 31 Summary ( continued ) u Inputs to design activities are diagrams built during analysis u Outputs of design are also diagrams that describe architecture of new system and detailed logic of programming components u Inputs, design activities, and outputs are different depending on whether a structured approach or an object-oriented approach is used u Architectural design adapts to development environment and decomposes design into layers