Systems Analysis & Design Sixth Edition Chapter 3 Requirement Modeling.
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Transcript of Systems Analysis & Design Sixth Edition Chapter 3 Requirement Modeling.
Systems Analysis & Design
Sixth Edition
Chapter 3
Requirement Modeling
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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
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Systems Analysis Phase Overview
● Systems Analysis Activities– Requirements
modeling– Data and process
modeling– Development
Strategies
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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
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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
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Systems Analysis Phase Overview
● Systems Analysis Skills– Analytical skills– Interpersonal skills
● Team-Oriented Methods and Techniques– Joint application development (JAD)– Rapid application development (RAD)
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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
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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
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Joint Application Development
● JAD Participants and Roles
Figure 3-4
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Joint Application Development
Figure 3-5
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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
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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
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Rapid Application Development
● RAD Phases and Activities
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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
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Modeling Tools and Techniques
● CASE Tools– Offer powerful modeling features– Systems analysts use modeling and fact-
finding interactively
● Functional Decomposition Diagrams– Functional decomposition diagram (FDD)
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Modeling Tools and Techniques
● Functional Decomposition Diagrams
Figure 3-9
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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
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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
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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
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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
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System Requirements Checklist
● Performance– The system must support 25 users online
simultaneously– Response time must not exceed four
seconds
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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
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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
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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
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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
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Fact-Finding
● Who, What, Where, When, How, and Why?
Figure 3-15
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Interviews
● Systems analysts spend a great deal of time talking with people
● Much of that time is spent conducting interviews
● Consists of 7 steps
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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
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Interviews
● Step 3: Develop Interview Questions– Creating a standard list of interview questions
helps to keep you on track and avoid unnecessary tangents
– Avoid leading questions– Open-ended questions
How is the task performed?– Closed-ended questions
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?
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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
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Interviews
Figure 3-18
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Interviews
Figure 3-19
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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
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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
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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
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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
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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
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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
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Other Fact-Finding Techniques
● Research– Newsgroups– Site visit
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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)
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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
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Documentation
● Software Tools– CASE Tools– Productivity Software
• Word processing, spreadsheets, database management, presentation graphics, histogram
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Documentation
● Software Tools– Graphics modeling software– Personal information managers
• Personal information manager (PIM)• Handheld computers• Personal digital assistants (PDAs)
– Wireless communication devices