Systems Analysis & Design Tenth Edition. Chapter 4. Requirements Modeling

Transcription

1 Systems Analysis & Design Tenth Edition Chapter 4 Requirements Modeling

2 Phase Description Systems analysis is the second of five phases in the systems development life cycle (SDLC) Uses requirements modeling and data and process modeling to represent the new system Before proceeding to the next phase, systems design, you will consider system development strategies 2

3 Systems Analysis Phase Overview Systems Analysis Activities Requirements modeling Data and process modeling Development Strategies 3

4 Introduction This chapter describes requirements modeling techniques and team-based methods that systems analysts use to visualize and document new systems Fact-finding techniques include interviewing, documentation review, observation, surveys and questionnaires, sampling, and research 4

5 Systems Analysis Phase Overview The overall objective is to understand the proposed project, ensure that it will support business requirements, and build a solid foundation for system development You use models and other documentation tools to visualize and describe the proposed system 5

6 Systems Analysis Phase Overview Systems Analysis Skills Analytical skills Interpersonal skills Team-Oriented Methods and Techniques Joint application development (JAD) Rapid application development (RAD) Agile methods 6

7 Joint Application Development User Involvement Users have a vital stake in an information system, and they should participate fully Successful systems must be user-oriented and users need to be involved 7

8 Joint Application Development JAD Participants and Roles JAD participants should be insulated from the distraction of day-to-day operations Objective is to analyze the existing system, obtain user input and expectations, and document user requirements for the new system 8

9 Joint Application Development JAD Participants and Roles Figure 4-3 9

10 Joint Application Development Figure

11 Joint Application Development JAD Advantages and Disadvantages Advantages Allows key users to participate effectively Disadvantages More expensive and can be cumbersome if the group is too large relative to the size of the project 11

12 Rapid Application Development Rapid application development (RAD) is a team-based technique that speeds up information systems development and produces a functioning information system RAD uses a group approach, but goes much further The end product of RAD is the new information system 12

13 Rapid Application Development RAD Phases and Activities 13

14 Rapid Application Development RAD Advantages and Disadvantages Advantages Systems can be developed more quickly with significant cost savings Disadvantages RAD stresses the mechanics of the system itself and does not emphasize the company s strategic business needs Might allow less time to develop quality, consistency, and design standards 14

15 Agile Methods Attempt to develop a system incrementally Agile Method Advantages and Disadvantages Are very flexible and efficient in dealing with change Frequent deliverables constantly validate the project and reduce risk Team members need a high level of technical and interpersonal skills May be subject to significant change in scope 15 15

16 Modeling Tools and Techniques Involves graphical methods and nontechnical language that represent the system at various stages of development CASE Tools Offer powerful modeling features Systems analysts use modeling and fact-finding interactively Functional Decomposition Diagrams (FDD) Data Flow Diagrams Unified Modeling Language 16 16

17 Modeling Tools and Techniques Functional Decomposition Diagrams (FDD) Top-down representation of a function or process Similar to an organization chart Figure

18 Modeling Tools and Techniques (Cont.) Data Flow Diagrams Data flow diagram (DFD) show how the system stores, processes, and transforms data Additional levels of information and detail are depicted in other, related DFDs FIGURE 4-10 This Visible Analyst DFD shows how books are added and removed in a library system 18 1

19 Modeling Tools and Techniques (Cont.) Use Case Diagrams Interaction between users and the system FIGURE 4-12 This table documents the credit card validation use case shown in Figure 4-11 FIGURE 4-11 This Visible Analyst use case diagram shows a sales system, where the actor is a customer and the use case is a credit card validation 19 1

20 Modeling Tools and Techniques (Cont.) Sequence Diagrams Shows the timing of interactions between objects as they occur FIGURE 4-14 This Visible Analyst sequence diagram shows a credit card validation process 20 2

21 System Requirements Checklist System requirement After gathering information about new system, system analyst needs to describe all system requirements. A feature that must be included in an IS to satisfy business requirement and be acceptable to users. Five general categories Outputs Inputs Processes Performance Controls 21

22 System Requirements Checklist Outputs The Web site must report online volume statistics every four hours, and hourly during peak periods The inventory system must produce a daily report showing the part number, description, quantity on hand, quantity allocated, quantity available, and unit cost of all parts sorted by part number 22

23 System Requirements Checklist Inputs Manufacturing employees must swipe their ID cards( 刷卡 ) into online data collection terminals that record labor costs and calculate production efficiency The department head must enter overtime hours on a separate screen 23

24 System Requirements Checklist Processes The student records system must calculate the GPA at the end of each semester As the final step in year-end processing, the payroll system must update employee salaries, bonuses, and benefits and produce tax data required by the IRS 24

25 System Requirements Checklist Performance The system must support 25 users online simultaneously Response time must not exceed four seconds 25

26 System Requirements Checklist Controls The system must provide log-on security at the operating system level and at the application level An employee record must be added, changed, or deleted only by a member of the human resources department 26

27 Future Growth, Costs, and Benefits Scalability( 擴展性 ) A scalable system offers a better return on the initial investment To evaluate, you need information about projected future volume for all outputs, inputs, and processes 27

28 Future Growth, Costs, and Benefits Total Cost of Ownership Total cost of ownership (TCO) is especially important if the development team is evaluating several alternatives One problem is that cost estimates tend to understate indirect costs 28

29 Fact-Finding Fact-Finding Overview The first step is to identify the information you need Who, What, Where, When, How, and Why? Difference between asking what is being done (current situation) and what could or should be done (future improvement) Know now first, and future comes later 29

30 Fact-Finding Who, What, Where, When, How, and Why? Figure

31 Interviews Systems analysts spend a great deal of time talking with people Much of that time is spent conducting interviews Consists of 7 steps 31

32 Interview Step 1: Determine the People to Interview Informal structures: some people have more influence or knowledge than appears on an organization chart. Step 2: Establish Objectives for the Interview Determine the general areas to be discussed List the facts you want to gather 32

33 Interviews Step 3: Develop Interview Questions Creating a standard list of interview questions helps keep you on track and avoid unnecessary tangents Avoid leading questions Formats of question: Open-ended questions How is the task performed? Closed-ended questions: limited and specific responses How many pc do you have in this department? Range-of-response questions On a scale of 1 to 10, how effective was your training? 33

34 Interviews Step 4: Prepare for the Interview Careful preparation is essential because an interview is an important meeting and not just a casual chat Limit the interview to no more than one hour Send a list of topics Ask the interviewee to have samples available 34

35 Interviews (Cont.) FIGURE 4-20 Sample message to a department head about interviews 35 3

36 Interviews (Cont.) 36 FIGURE 4-21 Sample message to confirm an interview 3

37 Interviews Step 5: Conduct the Interview Develop a specific plan for the meeting Begin by introducing yourself, describing the project, and explaining interview objectives Use engaged listening Allow the person enough time to think about the question Summarize main points After interview, summarize the session and seek a confirmation 37

38 Interviews Step 6: Document the Interview During the interview, note taking should be kept to a minimum After the interview, record the information quickly 50% of a conversation is forgotten within 30 minutes After the interview, send memo expressing appreciation, including the main points discussed so the interviewee has a written summary and can offer additions or corrections 38

39 Interviews Step 7: Evaluate the Interview In addition to recording the facts obtained in an interview, try to identify any possible biases Unsuccessful Interviews No matter how well you prepare for interviews, some are not successful 39

40 Other Fact-Finding Techniques Document Review Observation Seeing the system in action gives you additional perspective and a better understanding of the system procedures Plan your observations in advance Hawthorne Effect 40

41 Other Fact-Finding Techniques (Cont.) Research Can include the Internet, IT magazines, and books to obtain background information, technical material, and news about industry trends and developments Site visit 41 4

42 Other Fact-Finding Techniques Questionnaires and Surveys When designing a questionnaire, the most important rule of all is to make sure that your questions collect the right data in a form that you can use to further your fact-finding 42

43 Other Fact-Finding Techniques Sampling Systematic sample Stratified ( 分層的 )sample Random sample Main objective of a sample is to ensure that it represents the overall population accurately 43

44 Other Fact-Finding Techniques Interviews versus Questionnaires Interview is more familiar and personal Questionnaire gives many people the opportunity to provide input and suggestions Brainstorming Structured brainstorming (take turn to speak) Unstructured brainstorming (speak when you have an idea) 44

45 Documentation The Need for Recording the Facts Record information as soon as you obtain it Use the simplest recording method Record your findings in such a way that they can be understood by someone else Organize your documentation Some useful methods: DFD, flowcharts, sample forms, and screen captures 45

46 Documentation Software Tools CASE Tools Productivity Software Word processing, spreadsheets, database management, presentation graphics, histogram 46