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

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Main Contents

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

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1. What is requirement?

• ????IEEE
• (1)????????????????????????
• (2)???????????????????????????????????????????
• (3)?(1)?(2)????????????????????

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

• ?????????

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1. What is requirement?--??????? (2)

• ???????????????????,???????
• ?????,??????????????????????????????,?????????????
  ??
• ???????????????????,?????????(Problem Domain)
• ???????????,??????????,?????

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1. What is requirement?--????

• ????????????????????????,?????????????????????????
  ???
• ????,??????????????????(???),?????????????????????
  ??
• ????????????????????????
• ?????????????,????????????????

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1. What is requirement?--??

• ????????????????????????
• R1???????,??????,?????????
• R2???????30???????,????????????
• ????
• ????????????????
• ????
• ????????,????????????????

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1. What is requirement? --????

• ???????????????????????,???????????
• ????????
• (1)?????(??)???
• (2)?????????????????

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1. What is requirement?--?????

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• ??????,???????????,???????????????
• ?????????????????????????

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1. What is requirement?--????????????????????

• ??????????E ?????????S ?????R
• ???????????E,??S,??
• ?????????
• (1)????????E
• (2)????????S?????R
• (3) ??????????
• ?????????
• ????,?? R
• ??????,???????E
• ?????,???????S,??

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1. What is requirement?--?????IEEE

• ????(Functional Requirement)
• ????????????,?????????????,??????????????,????????
  ?????????????????????????????
• ????(Performance Requirement)
• ????????????????????,??CPU???????????
• ????(Quality Attribute)
• ?????????,???????????????????,????????????????
• ????(External Interface)
• ???????????????????,????????????????????
• ??
• ??????????????,????????????

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1. What is requirement?--????????
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1. What is requirement?--????????

• ????
• ??????????,?????????(Objective),??????????????
• ????????????????????,??????????(Vision)
• ????
• ????????????????????????,???????????????
• ??
• ??????
• ?????
• ?????
• ?????
• ??????????,???????????????????????,??????
• ???????????????,?????????????,?????????????

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1. What is requirement?--????????

• ???????????????????????
• ??????????????,??????????????????,?????????
• ????????????????,??????????,?????????????,????????
  ????????
• ??????????????????????,??????????

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

• ?????????????????
• ?????????

????
????
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2. Why RE ?--From theory (2)????

• ??
• ???1????????,??????????
• ???2????????????,??????????????????
• ?????????
• ??
• ??

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

• ?????
• ???????

• ??
• ??
• ?????
• ?????
• ????
• ??

??????
??????
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2. Why RE ?--From theory (4)????

• ????
• ??????
• ????(??????)???????????????????
• ????????,?????????????????????
• ?????????????(??? VS ????)?????

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2. Why RE ?--From Practices (1)
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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
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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
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2. Why RE ?--From Practices (4) , Standish
Group1995

• ????
• ????(????)
• ??????
• ???????
• ???????
• ????????
• ????
• ???????
• ????,????
• ???????????53.9
• ???????????60.9

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2. Why RE ?--From Practices (5) , ESPITI,1996

• ??????ESI
• ??????????????ESPITI
• 17??????3800???

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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

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2. Why RE ?--????

• ??????????
• ????????????????????????????????????????
• ???????????????????????????
• ???????????????????????????????

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3. Activities of RE

• ??????????

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3. Activities of RE--???????

• Inception
• Elicitation
• Elaboration
• Negotiation
• Specification
• Validation
• Requirements management

Elicitation
Analysis
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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

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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?

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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

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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

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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.

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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

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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

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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

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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

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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

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The End

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