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Computing and SE II Chapter 4: Requirements Engineering

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Computing and SE II Chapter 4: Requirements Engineering Er-Yu Ding Software Institute, NJU 3. Activities of RE--- Negotiating Requirements Agree on a deliverable ... – PowerPoint PPT presentation

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Title: Computing and SE II Chapter 4: Requirements Engineering


1
Computing and SE II Chapter 4 Requirements
Engineering
  • Er-Yu Ding
  • Software Institute, NJU

2
Main Contents
  1. What is requirement?
  2. Why RE (requirements engineering)?
  3. Activities of RE

3
1. What is requirement?
  • ????IEEE
  • (1)????????????????????????
  • (2)???????????????????????????????????????????
  • (3)?(1)?(2)????????????????????

4
What is requirement?--???????(1)
  • ?????????

5
1. What is requirement?--??????? (2)
  • ???????????????????,???????
  • ?????,??????????????????????????????,?????????????
    ??
  • ???????????????????,?????????(Problem Domain)
  • ???????????,??????????,?????

6
1. What is requirement?--????
  • ????????????????????????,?????????????????????????
    ???
  • ????,??????????????????(???),?????????????????????
    ??
  • ????????????????????????
  • ?????????????,????????????????

7
1. What is requirement?--??
  • ????????????????????????
  • R1???????,??????,?????????
  • R2???????30???????,????????????
  • ????
  • ????????????????
  • ????
  • ????????,????????????????

8
1. What is requirement? --????
  • ???????????????????????,???????????
  • ????????
  • (1)?????(??)???
  • (2)?????????????????

9
1. What is requirement?--?????
  • ????????????????
  • ????????????
  • ?????????
  • ??????,???????????,???????????????
  • ?????????????????????????

10
1. What is requirement?--????????????????????
  • ??????????E ?????????S ?????R
  • ???????????E,??S,??
  • ?????????
  • (1)????????E
  • (2)????????S?????R
  • (3) ??????????
  • ?????????
  • ????,?? R
  • ??????,???????E
  • ?????,???????S,??

11
1. What is requirement?--?????IEEE
  • ????(Functional Requirement)
  • ????????????,?????????????,??????????????,????????
    ?????????????????????????????
  • ????(Performance Requirement)
  • ????????????????????,??CPU???????????
  • ????(Quality Attribute)
  • ?????????,???????????????????,????????????????
  • ????(External Interface)
  • ???????????????????,????????????????????
  • ??
  • ??????????????,????????????

12
1. What is requirement?--????????
13
1. What is requirement?--????????
  • ????
  • ??????????,?????????(Objective),??????????????
  • ????????????????????,??????????(Vision)
  • ????
  • ????????????????????????,???????????????
  • ??
  • ??????
  • ?????
  • ?????
  • ?????
  • ??????????,???????????????????????,??????
  • ???????????????,?????????????,?????????????

14
1. What is requirement?--????????
  • ???????????????????????
  • ??????????????,??????????????????,?????????
  • ????????????????,??????????,?????????????,????????
    ????????
  • ??????????????????????,??????????

15
2. Why RE ?--From theory (1) ???
  • ?????????????????
  • ?????????

????
????
16
2. Why RE ?--From theory (2)????
  • ??
  • ???1????????,??????????
  • ???2????????????,??????????????????
  • ?????????
  • ??
  • ??

17
2. Why RE ?--From theory (3)????
  • ?????
  • ???????
  • ??
  • ??
  • ?????
  • ?????
  • ????
  • ??

??????
??????
18
2. Why RE ?--From theory (4)????
  • ????
  • ??????
  • ????(??????)???????????????????
  • ????????,?????????????????????
  • ?????????????(??? VS ????)?????

19
2. Why RE ?--From Practices (1)
20
2. Why RE ?--From Practices (2) ,Standish Group
1995
????????? ????
???? 15.9
?????? 13.9
??????? 13.0
??????? 9.6
??????? 8.2
???????? 7.7
???? 7.2
????? 5.3
???????? 2.9
???? 2.4
?? 13.9
21
2. Why RE ?--From Practices (3) , Standish
Group1995
????????? ????
???????? 13.1
?????? 12.4
???? 10.6
??????? 9.9
???????? 9.3
???? 8.7
???? 8.1
??????? 7.5
??IT?? 6.2
?????? 4.3
?? 9.9
22
2. Why RE ?--From Practices (4) , Standish
Group1995
  • ????
  • ????(????)
  • ??????
  • ???????
  • ???????
  • ????????
  • ????
  • ???????
  • ????,????
  • ???????????53.9
  • ???????????60.9

23
2. Why RE ?--From Practices (5) , ESPITI,1996
  • ??????ESI
  • ??????????????ESPITI
  • 17??????3800???

24
2. Why RE ?--People think requirements is main
troubles
  • There is little doubt that project requirements
    are the single biggest cause of trouble on the
    software project front. Study after study has
    found that, where there is a failure,
    requirements problems are usually at the heart of
    the matter. GLAS98
  • 'as much as 90 of subsequent troubles can be
    traced back to erroneous original
    specifications. BRUC89

25
2. Why RE ?--????
  • ??????????
  • ????????????????????????????????????????
  • ???????????????????????????
  • ???????????????????????????????

26
3. Activities of RE
  • ??????????

27
3. Activities of RE--???????
  • Inception
  • Elicitation
  • Elaboration
  • Negotiation
  • Specification
  • Validation
  • Requirements management

Elicitation
Analysis
28
3. Tasks of RE---Inception
  • Establishing project vision and scope
  • basic understanding of the problem (Objectives)
  • the nature of the solution that is desired
    (Vision)
  • How many things needed to developing the solution
    (Scope)
  • Stakeholders Analysis
  • the people who want a solution
  • Characteristics of Stakeholders
  • the effectiveness of preliminary communication
    and collaboration between the customer and the
    developer
  • Make usage of characteristics of Stakeholders

29
3. Activities of RE---Inception
  • Identify stakeholders
  • who else do you think I should talk to?
  • Recognize multiple points of view
  • Understand stakeholders
  • Work toward collaboration
  • Establish common objectives, vision and scope
  • The first questions
  • Who is behind the request for this work?
  • Who will use the solution?
  • What will be the economic benefit of a successful
    solution
  • Is there another source for the solution that you
    need?

30
3. Tasks of RE---Elicitation
  • From where? (Source)
  • Stakeholders, hard data, environments
  • Elicit what? (Content)
  • How many requirements
  • How many elicit activities
  • Which requirements in each elicit activities
  • How to elicit (technique)
  • Interview, prototype, observe, scenario (use
    case)
  • Up to source and content

31
3. Activities of RE--- Eliciting Requirements
  • the goal is
  • to identify the problem
  • propose elements of the solution
  • negotiate different approaches, and
  • specify a preliminary set of solution
    requirements

32
3. Activities of RE--- Elicitation Work Products
  • a statement of need and feasibility.
  • a bounded statement of scope for the system or
    product.
  • a list of customers, users, and other
    stakeholders who participated in requirements
    elicitation
  • a description of the systems technical
    environment.
  • a list of requirements (preferably organized by
    function) and the domain constraints that apply
    to each.
  • a set of usage scenarios that provide insight
    into the use of the system or product under
    different operating conditions.
  • any prototypes developed to better define
    requirements.

33
3. Activities of RE---Elaboration
  • Create an analysis model that identifies data,
    function and behavioral requirements
  • ?????
  • Analysis models can describe requirements more
    precise
  • In analysis, solution requirements can be deduced
  • Elaboration and elicitation are interweaved
    activities
  • Get something, understand them, and need more

34
3. Activities of RE--- Negotiating Requirements
  • Agree on a deliverable system that is realistic
    for developers and customers
  • Identify the key stakeholders for conflicts
  • These are the people who will be involved in the
    negotiation
  • Determine each of the stakeholders win
    conditions
  • Win conditions are not always obvious
  • Negotiate
  • Work toward a set of requirements that lead to
    win-win

35
3. Activities of RE---Specification
  • Writing what you know
  • For communication to
  • Developers
  • Projects managers
  • Users
  • Testers
  • User manual writers
  • With documents
  • Using template
  • Using writing techniques

36
3. Activities of RE--- Validating Requirements
  • Assure the specifications are according to users
    requirements
  • Misunderstanding
  • Writing error
  • missing
  • Validating focus
  • See textbook
  • Validating with some standards
  • Good enough, but not perfect

37
3. Activities of RE--- Requirements management
  • Establishing baseline after requirements
    development
  • Putting RE products into Software Configuration
    Management
  • Maintaining track matrix
  • Knowing the impacts of each requirements
  • Change control
  • Not every change is forbidden
  • Not every change is permitted

38
The End
  • Recommend Paper
  • Software Requirements A Tutorial
  • The World and The Machine
  • Next Lecture
  • Requirement Analysis
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