Luiz Marcio Cysneiros
Fall 2015 http://www.mathstat.yorku.ca/~cysneiro/courses.htm
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Requirements engineering : processes and techniques
Gerald Kotonya and Ian Sommerville.
Publication info: Chichester ; New York : J.
Wiley & Sons, c1998. ISBN: 0471972088
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Oral Presentation +
Leading discussion 45%
Final exam 55% http://www.mathstat.yorku.ca/~cysneiro/courses.htm
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email office
cysneiro@yorku.ca
TEL Building 3053
Office Hours – Tuesday: 2:30 PM to 3:45 PM
Wednesday 5:00 PM to 6:30 PM
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http://www.mathstat.yorku.ca/~cysneiro/courses.htm
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RE State-of-the-art for research and Practice
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What does a RE do ?
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Techniques
•
Methods
•
Process
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Understanding RE
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Research in RE
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Existing Methods
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Where it will lead us ?
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Alternatives ?
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• Introduction
• Elicitation
• Modelling
• Analysis
• Management http://www.mathstat.yorku.ca/~cysneiro/courses.htm
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• Software-Intensive Systems
• Software vs Systems ?
– Software Alone is useless
– Hardware Alone is useless
– Both only exist when used to support any human activity
– Software+Hardware+People+activities
• Systems
• Intensive use of software systems http://www.mathstat.yorku.ca/~cysneiro/courses.htm
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• Software systems present opportunities for change
– It may be complex but should also be adaptable
– Changes very quickly and some times very frequently
– A New System may change human activities in many significant ways
• Paperless Hospitals
• Virtual Doctors
• Virtual Surgeries
• Phone Chat
• facebook
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• Software Systems became Ubiquitous
– Even Refrigerators have software systems today
– However, we are frequently disappointed with them
– If it doesn’t work chances are :
• Who designed didn’t understood what was needed
• It is been used for different purposes than the original intended
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(Macmillan English Dictionary)
1. something that is needed in order for something to happen:
– Check the car’s fuel requirements.
– Good insulation can cut the energy requirements of a house by more than half.
2. something that a rule, law, contract, etc. states that you must do:
– Do these goods comply with our safety requirements?
– requirement of: It is usually a requirement of banks and investors that a new company is formed to effect the management buy-out.
– requirement for: Applicants must satisfy the requirements for admission to the university.
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System: (Macmillan English Dictionary)
1.
[count] a set of connected things that work together for a particular purpose:
– a central heating system
– I decided to install a security system to prevent any break-ins.
– the city’s inadequate public transportation system
System: some part of a reality that can be observed to interact with its environment a set of interrelated components, or sub-systems, with a particular purpose.
1) there are 2 components at least,
2) each of which is related (directly or indirectly) to every other component and,
3) no sub set of which is unrelated to any other subset.
Ackoff, Russell L., (1971). Towards a System of Systems Concepts. Management
science, 17(11), 661-71.
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• Software crises continues
– Denver Airport
• More than 50 million US $ due to errors in the baggage control system
– London Ambulance Service
• The system was deactivated one day after its deployment due to many errors. Most of them related to non-functional requirements such as:
Safety, Reliability and Usability http://www.mathstat.yorku.ca/~cysneiro/courses.htm
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• Flaws in the Production Process
Unhappy Clients High costs http://www.mathstat.yorku.ca/~cysneiro/courses.htm
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• Questionnaire sent to 3.805 companies showed:
• For the Analysts, Major problems are:
– Requirements specification (53%)
– Requirements Management (43%)
– Documentation (36%)
– Test (35%) http://www.mathstat.yorku.ca/~cysneiro/courses.htm
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• Requirements Management (Also know as
Requirements Engineering – RE) is seen as one of the most important problems to be overcome in order for companies to achieve level 2 in the SEI’s (Software Engineering
Institute – Carnegie Mellon) CMM
(Capability Maturity Model)
• SEI has recently released a package aiming to transfer technology in RE to facilitate companies’ certification
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26% of the Software projects were considered a success.”
Standish Group, CHAOS Report, 2000
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Meaning that 74% have FAILED !
Standish Group, CHAOS Report, 2000 http://www.mathstat.yorku.ca/~cysneiro/courses.htm
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56% of the errors in a software can be traced back to the requirements phase”
• The later an error is detected the more expensive is to fix it.
• Many errors are done during Requirements elicitation and analysis
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• Many errors in requirements can (and should) be detected early in the software development life cycle.
• Typical errors include: Use of incorrect facts, omission, inconsistency and ambiguity.
• Errors in requirements specification are one of the major concerns for software industry.
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200 x
Cost to
Repair
Analysis Design Code Unit Test Integration
Test
Maintenance
Stage when the Error is found
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“ Requirements engineering is a sub-area of
Software Engineering that studies the process of defining the requirements for a software-to-be. It is a new area started in 1993 when the 1 st
International Symposium on RE was organized.
The process for defining requirements is an interface between the desires and the needs of the clients and a future implementation of these requirements as a software.”
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• Understand the needs and support the client’s desires.
• Provide the Requirements Engineer with methods, techniques and tools to help on the process of understanding and registering what a software must do.
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• Brook adds:
“The most difficult part of building a software system is to decide, precisely , what must be built. No other part of the work can undermine so badly the resulting software if not done correctly. No other part is so difficult to fix later.”
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• Personality and status of stakeholders
• The personal goals of individuals within an organization
• The degree of political influence of stakeholders within an organization
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• Lack of stakeholder involvement
• Business needs not considered
• Lack of requirements management
• Lack of defined responsibilities
• Stakeholder communication problems
• Over-long schedules and poor quality requirements documents
• Many confuse it with Design
• Pressure from the Market
– “It has to be ready next week”
• Clients keep adding and changing things
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• Process improvement is concerned with modifying processes in order to meet some improvement objectives
• Improvement objectives
– Quality improvement
– Schedule reduction
– Resource reduction
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• What are the problems with current processes?
• What are the improvement goals?
• How can process improvement be introduced to achieve these goals?
• How should process improvements be controlled and managed?
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• Process maturity can be thought of as the extent that an organization has defined its processes, actively controls these processes and provides systematic human and computer-based support for them.
• The SEI’s Capability Maturity Model is a framework for assessing software process maturity in development organizations
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Level 1
Initial
Level 5
Optimizing
Le vel 4
Managed
Level 3
Defined
Le vel 2
Repeatable http://www.mathstat.yorku.ca/~cysneiro/courses.htm
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• Initial level
– No defined RE process. Suffer from requirements problems such as requirements volatility, unsatisfied stakeholders and high rework costs. Dependent on individual skills and experience.
• Repeatable level
– Defined standards for requirements documents and policies and procedures for requirements management.
• Defined level
– Defined RE process based on good practices and techniques. Active process improvement process in place.
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• Managed level
– Detailed measurements of both process and product quality are collected and used to control the process.
• Optimizing level
– The organization has a continuous process improvement strategy, based on objective measurements in place.
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• RE processes can be improved by the systematic introduction of good requirements engineering practice
• Each improvement cycle identifies good practice guidelines and works to introduce them in an organization
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• Structured Analisys
• Structured Project
• Essential Analysis
• Entity-Relationship Model
• Objects
• CASE
• Automatic Genaration of Applications http://www.mathstat.yorku.ca/~cysneiro/courses.htm
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Ideal
Very
High
Level
Abstract
Conventional
Goal
Talk Specification Code
High
Level
Low
Level
Machine
Level
Concrete
Informal Linguistic Level Formal http://www.mathstat.yorku.ca/~cysneiro/courses.htm
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Von Neumann:
“There is no sense in being precise when you don’t even know what you are talking about”
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• Information System
• Engineering Systems
• Organizations Producing Software
• Models http://www.mathstat.yorku.ca/~cysneiro/courses.htm
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The Blank Page Fallacy
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The Completeness Fallacy
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Social Aspects Involved http://www.mathstat.yorku.ca/~cysneiro/courses.htm
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Clients
Users
Needs
Limitations
Impossibilities
Technological Infra-Structure http://www.mathstat.yorku.ca/~cysneiro/courses.htm
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• Software Requirements
– Sentences that express clients’ needs and establish the desired quality http://www.mathstat.yorku.ca/~cysneiro/courses.htm
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• Functional Requirements
– FR are the requirements that are directly related to the software functionality.
–
What the system must do !
• Non-Functional Requirements
– NFRs express constraints that a software must comply with.
– Can be seen as specific qualities that a software must have
– “How” the software must do the “What”
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Ex: Safety, accuracy, usability,security
• Requirements -1 ( Inverse Requirements )
– IR establish conditions that must never happen
– Frequently associated to an NFR
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Clients
FR
Users
Needs
Impossibilities
IR
Limitations
NFR
NFR
Technological Infra-Structure
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• The system should provide a form to enter results for clinical tests performed for a client (FR)
• Depending on the result of the test, only the Supervisor can entry the result for this patient. E.g. Glucose over 8.0 (NFR
Safety)
• The system should give the client a receipt. This should take no longer than 8 sec (FR “.” NFR Performance)
• The system can not erase any client information (IN)
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• Universe of Discourse
– Is the context in which the software should be developed and operated. UofD includes all sources of information and all people related to the software. These people are also known as the actors of this universe. UofD is a reality circumstantiated by the set of goals defined by those who demand the software
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Universe of Discourse
Macrosystem
Software
System http://www.mathstat.yorku.ca/~cysneiro/courses.htm
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organization software hardware
Information
System
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An SADT Model for the Definition of Requirements
UofD
UofD
Select
Personel
UofD
Select
Method
Soft. Eng. Viewpoints clients method
Elicit facts
Model requirements model
Analyse tools
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• Not Waterfall
• Not Spiral
• Not Iterative http://www.mathstat.yorku.ca/~cysneiro/courses.htm
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•
Requirements Engineering: Processes and Techniques by Ian
Sommerville, Gerald Kotonya (September 1998)
John Wiley & Son Ltd; ISBN: 0471972088 Amazon.com Sales Rank:
188,502
• System Requirements Engineering by Pericles Loucopoulos, Vassilios
Karakostas (June 1995)
McGraw Hill Text; ISBN: 0077078438 Amazon.com Sales Rank:
1,067,908
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Software Requirements & Specifications : A Lexicon of Practice,
Principles and Prejudices by Michael Jackson (July 1995)
Addison-Wesley Pub Co; ISBN: 0201877120 Amazon.com Sales Rank:
38,607
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•
Exploring Requirements : Quality Before Design by Donald C. Gause and Gerald M. Weinberg (September 1989) Dorset
House; ISBN: 0932633137 Amazon.com Sales Rank: 13,641
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Mastering the Requirements Process by Suzanne Robertson, James
Robertson (May 4, 2000) Addison-Wesley Pub Co; ISBN: 0201360462 ;
Dimensions (in inches): 0.93 x 9.50 x 7.66 Amazon.com Sales Rank: 7,392
•
Managing Software Requirements: A Unified Approach (The Addison-
Wesley Object Technology Series)by Dean Leffingwell, Don Widrig
(November 1999),Addison-Wesley Pub Co; ISBN: 0201615932 Dimensions
(in Inches): 1.13 x 9.46 x 7.76 Amazon.com Sales Rank: 14,447
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• Requirements Engineering - a roadmap - Nuseibeh,
Easterbrook – First Presentation
•
•
[Goguen94] - Goguen, J.A. and Linde, C. - Techiques for
Requirements Elicitation, In Proceedings of the First
IEEE International Symposium on Requirements
Engineering, San Diego, Ca, IEEE Computer Society Press
- 1994, pp 152-164.
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[Goguen94a] - Goguen, Joseph - Requirements
Engineering as the reconciliation of social and technical issues - in Requirements Engineering: Social and
Technical Issues edited by Joseph Goguen and Marina
Jirotka - Academic Press 1994.
• Download from course page
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