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Requirements - Why What and How? Sriram Mohan. Outline Why ? What ? How ?

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Presentation on theme: "Requirements - Why What and How? Sriram Mohan. Outline Why ? What ? How ?"— Presentation transcript:


2 Requirements - Why What and How? Sriram Mohan.

3 Outline Why ? What ? How ?

4 Why Requirements

5 Some facts 250 billion dollar industry 31% projects cancelled(money lost 81 billion dollars) 52.7% cost 189% of their original estimates 4

6 Biggest Reasons for Project Success and Failure

7 Project Failure Lack of user input (13%) Incomplete requirements (12%) Changing requirements (12%)

8 Project Success User involvement (16%) Executive management support (14%) Clear statement of requirements (12%)

9 8

10 Defects by Development Phase Requirements – 31% Design – 25% Coding – 12% Documentation – 16% Bad fixes – 16%

11 Cost to Fix Errors 10 Requirements Design Coding Unit Test Acceptance Test Maintenance 1 5 25 50 125 500

12 Why ? Requirements errors are likely to be the most common class of error Requirements errors are likely to be the most expensive to fix 11

13 What is a Software Requirement?

14 1.A software capability needed by the user to solve a problem to achieve an objective 2.A software capability that must be met or possessed by a system or system component to satisfy a contract, standard, specification or other formally imposed documentation 13

15 What is Software Requirements MGMT?

16 What is Software Requirements Management? The process of systematically, eliciting, organizing and documenting requirements for the software system, and a process that establishes and maintains agreement between the customer and the project team on the changing requirements of the system. 15

17 16

18 What does it involve? Understand the need - the problem to be solved Propose features - how the need will be resolved Requirements are the specific conditions that are imposed on the solution 17

19 18 Needs Features Requirements Problem Domain Solution Domain

20 Software Lifecycle Process Models

21 20

22 Waterfall Model Manufacturing life cycle model Assumes – multi-stage development cycle – completely separate stages – output of one stage is input for next – each stage complete before next is begun

23 Waterfall Stages Requirements DesignCodingTestingMaintenance

24 Advantages Much better than chaos! Clearly defined stages help with – planning, scheduling – management, organization – accountability, control

25 Disadvantages Not very practical (do not know requirements in the beginning) Customer sees nothing until last step Change is Anathema

26 Spiral Model Incremental – more feedback from customer Risk analysis – more rigorous analysis of risk at each stage 25

27 Spiral Model

28 Iterative (or Incremental) Approach Four phases – Inception – Elaboration – Construction – Transition 27

29 Iterative(or Incremental) Approach An iteration is a sequence of activities with an established plan and evaluation criteria, resulting in an executable of some type Each phase goes under a # of iterations 28

30 Management Environment Business Modeling Implementation Test Analysis & Design Preliminary Iteration(s) Iter. #1 Phases Iterations Iter. #2 Iter. #n Iter. #n+1 Iter. #n+2 Iter. #m Iter. #m+1 Deployment Configuration Mgmt Requirements ElaborationTransitionInceptionConstruction Workflows group activities logically In an iteration, you walk through all activities Process Workflow Support Workflow Rational Unified Process Model

31 Team Project Process Modified Waterfall model will be used in 371 You may choose any model you desire during implementation in 372 30

32 Software Development Is this a team activity? Why? 31

33 Requirements Team Skills 1.Analyzing the Problem 2.Understanding User and Stakeholder Needs 3.Defining the System 4.Managing Scope 5.Refining the System Definition 6.Building the Right System

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