Post on 28-Dec-2015
transcript
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• Another Definition for Requirements:– An externally Observable Characteristic of a
Desired System
• 2 Buttons in a mouse– If the user needs 2 buttons this is a requirement– If the user only need a way of moving slides
back and forth, this is too detailed to be a requirement
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Tackling the problem not the solution
My Elevator is too slow• My Elevator is slow
•You have a throughput problem not a speed problem !
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Tackling the problem not the solution
My Elevator is too slow
• Well it’s a problem because people complaint about the lines •As better as needed for stopping complaints
•Why is that a problem ?•How better should it be?
•How About Adding mirrors to the wall ?
• My Elevator is slow
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Why do We Need Requirements Engineering?
von Neumann:
“There is no sense in being precise when you don’t even know what you are talking about”
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Basic Needs for Elicitation
(Questions from Polya)
• What is unknown?
• Do you know any related problem?
• Can you reinvent the problem?
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Elicitation
Elicit [Var. elicit + make it clearer + extract]1.discover, make explicit, get as much information
as possible to understand the object being studied.
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Identifying Sources of Information
• Actors in the Universe of Discourse – Clients– Users– Developers
• Documents• Books• Software Systems• COTS
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Who is related to the software?
interested
customer
developers
users
clients
OwnerEspecialist
Hired
Partner
Third party clients
Investor
Quality Control (QC)Technical writers
Software Engineer
clients
Non-clients
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Heuristics to identify sources of information
• Who is the client?• Who owns the system?• Is there any customized system available?• What are the books related to the
application?• Is it possible to reuse software artifacts? • What are the documents most cited by the
actors of UofD?
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Abstract tree of people interested in the software
CFO
Accounting Manager
Acquisition Sales
Revenue Manager
Emplyee A Employee B
•requirements
•requirements •requirements
•requirements •requirements
•requirements
•requirements
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Facts gathering• Document Reading• Observation• Interviews• Reunions • Questionnaires• Anthropology• Active participation from actors• Protocol Analysis• Reverse Engineering• Reuse
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Enterviews Interviews
• Structured– Usually 1 to 1– Can be 1 to n or n to 1– Requires some knowledge about the problem to
formulate the questions
• Tape it ?
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Structured Interview
• What to ask– Objective questions with precise target– One question should be related to the other
• How to ask
• Ask whom
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Non-Structured Interview
• More flexible– But still with a pre-defined guideline of
questions
• Informal– But always keep control
• Mostly used during exploratory phases– Sometimes interesting to be used later also to
solve conflicts or to further explore alternatives
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Tacit Knowledge
• The kind of knowledge that is trivial for the actor being interviewed but not for the interviewer
• Because it is trivial, people almost never remebers to mention it. The interviewer in his/her turn, not knowing about the tacit knowledge can not ask about it.
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Interviews
• Follow Up – Essential – After the interview write down what you
understood– Send it to the user(s) involved and ask for a
feedback (Have I got it right?)– Ask if the user(s) want to add anything
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Interviews
• +– direct contact with the actors– Can validate information immediately
• -– Tacit knowledge– Cultural diferences
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Reading
• Books– Summary per chapter– Highlight the most important parts– Use a key-word index– vocabulary
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Reading
• Macrosystem Documents (A more careful reading)– Underline repeated words
– Synonymies
– Take note of unknown terms
– Search for relationships among terms
– Vocabulary
– Try to understand and document the structure of the documents
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Reading
• Macro system Documents – Understand the structure of the documents– How they relate/point to each other
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Document Reading
• +– Easy access to different sources of information
– Volume of information
• -– Information can be very dispersed
– Considerable amount of work is required to identify relevant facts
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Questionnaires
• What should one ask ?– Asks for some knowledge about the problem
• Therefore you should have a minimum understanding about the problem
– similar to the structured interview
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QuestionnairesTypes• qualitative
– Allows the one answering to further considerations– Makes a later analysis more difficult– Control questions – We can stimulate conflicts in order
to verify the consistency of what is being told
• quantitative– grading ( Yes, No/ Good, mdeium, bad/ 0,1,2,3,4)– Question has to be well formed to allow a good
distribution of the answers
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Examples
• Quantitative
05
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Nu
m. d
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esp
ost
as
5. A XXX mantém dados estatísticos sobre o processo de desenvolvimento de software?
SIMNÃO
5 - XXX keeps statistical data about the software development process
Nu
mb
er o
f A
nsw
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No Yes
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Examples
05
1015202530354045505560
Nu
m. d
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1 2 3 4 5
8. Durante o processo de produção é verificada uma alteração nos requisitos. Esta alteração:
(Não é registrada) (É registrada, mas não no documento de requisitos)
(É registrada formalmente no documento de requisitos)
8 – How easyly can you retrieve information from Patient’s Medical Records ?
Nu
mb
er o
f A
nsw
ers
Not easy at all Kind of easily easily
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Examples
• QualitativeHow do you see your background regarding the
development of quality software? What do you think would be necessary to improve your performance? What knowledges would like to get? Why ?
– Objective: verify the opinion regarding training policy
– Why ?: A mature organization has to have well defined training policies. Control question.
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Questionnaires
• +– Standard questions– Statistical treatment possible
• -– Answers are constrained– Few or no interaction/participation– Number of questionnaires returned can be
disappointing
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Meetings• An extension of an interview or
• Direct and Intense participation– Short and intense periods– focus
• Brainstorm
• JAD
• Requirements Workshop – Uses facilitators– Previous planning
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Meetings
Requirements Workshop
• Preparation– Adequate place– Choosing Participants– Prepare the material ahead– agenda
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Meetings
Requirements Workshop
• Facilitator– Trained– Team spirit– Respected by all participants– “Powerful” enough to make decisions when
conflicts arise
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Meetings
Requirements Workshop • During the meeting
– relax participants– Focus on ideas not people– Be open to brainstorming – Register the meeting (minutes are highly
desirable)
– follow up e agenda for next meetings
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Meetings
Requirements Workshop
• Problems– People with a reign attitude– Passive attitude– People arriving late– Negative/mocking comments– It is always hard to resume a meeting after a
disruptive interruption
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Meetings
Brainstorm• Generate and condensate ideas• Frequently, the best ideas are combinations
of two or more ideas• Prioritize the ideas • It is better to be done locally, but it is
possible to have it over the web or using video-conference
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Meetings
Brainstorm
Phase I – Generating ideas• Goal: Generate the more ideas possible
• Rules– Do not allow critics or debate at this point– Let the imagination flows– Change and combine ideas
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MeetingsBrainstormPhase II –Reducing the number of ideas• Discard ideas that are not worth to invest• Group ideas – make meaningful names and group
ideas according them• Anotate small descriptions about the rationale
regarding the ideas and its authors• Prioritize
– vote
– categorize - critical, important, useful
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Meetings
JAD (Joint Application Design)
Involves• Objectives• System Requirements• External Project
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Meetings
Principles of JAD
• Group dynamic• Visual resources• Organized and rational process• Documenting using the idea of “What you see is
what you get” (WYSISYG)
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Meetings
JAD
Target• Identify high level (abstract) requirements• Define and Associate the scope• Plan the activities for each phase of the project• Post and approve resulting documents
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Meetings
JAD’s Phases
• Customization• Meetings
– Present the tasks
– Join ideas
– Evaluate
– Compromise
• Closing
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MeetingsJAD - Documents
Requirements– High level requirements
– Goals
– Anticipated benefits
– Strategies and future considerations
– Hypothesis and constraints
– Security, auditing and control
– System scope
– System users and their locations
– Functional areas outside the application
•
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Meetings
JAD - Documents
Plans:– Participant matrix
– Identification of the JAD/PROJECT
– Estimative
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JAD
• Used to speed up the investigation of system requirements, design a solution, define new procedures
• Critical Factor : To have ALL the relevant participants present
• Typically used for 3-6 months long projects.– Larger projects may require one JAD at the
beginning of each iteration
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Observation
• To watch people while they’re doing their jobs
• Take careful notes
• Be careful about Taping/Recording
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Observation
• +– low cost– Easy task (Not always)
• -– Depends on the actor not being influenced
because he knows he’s being observed– Depends on the observer’s skills– Tends to be superficial due to the weak
exposition to the UofD
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Protocol Analysis
• Analyze the work the person “besides” you is doing
• Speak loud during the tasks• Some people claim during an interview one
can use the memory instead of what he/she really does
• Goal – identify the rationale used to perform a task
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Protocol Analysis
• +– Elicit facts not shown
• Easier to avoid tacit knowledge
– Better understanding about tasks and rationales behind them
• -– Focus on performance (not necessarily true)– Not always what I say is what I do !!!– May be hard to use in some environments (e.g.
hospitals)
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Ethnography
• Deeply integrate to the environment
• The Analyst becomes a client or even the responsible for some tasks
• Slow
• Long Term results