3. Software Process PROC-1 Venkat Subramaniam Whats a process? - - PDF document

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Venkat Subramaniam

• 3. Software Process

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Venkat Subramaniam

What’s a process?

• Set of activities in creating software
• It involves creativity

– hard to automate – Requires human judgment

• No one approach to create software

– Different organizations and groups within

• rganization do different things

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Activities

• Requirements specification
• Analysis
• Design
• Implementation
• Testing
• Maintenance and evolution

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Different Approaches

• Waterfall
• Spiral
• Iterative & Incremental Development
• Agile

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Waterfall Model

Requirements Analysis Design Implementation &Testing Integration Maintenance

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What’s good about Waterfall

• Easy to plan

– (but hard to execute)

• Easy to explain the progression of the

project

– (but may not be the reality, however)

• Help with budgeting and estimating time

upfront

– (often overrun though)

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Problems with Waterfall

• Sequential steps
• Not easy to work with
• Each stage expected to be complete and

well done

• Assumes requirements are well

understood

– (Are they ever?)

• Hard to keep up with change

– (change is the only constant)

• Hard to meet users needs

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Spiral Model

Analysis Requirements Specification Integration Design Implementation & Unit Testing

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What’s good about Spiral

• Recognizes that software applications

need to evolve

• Each version may be one loop though the

spiral

• You have a chance to revisit and modify

things that may not be correct or adequate

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Problems with Spiral

• Each cycle may be long – waterfall
• If each cycle is large, hard to modify

system

– change may be prohibitive

• May be expensive
• If cycles are short, planning may be hard

– Project management and reporting will be an issue

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Iterative & Incremental Dev.

• Consider waterfall as a guiding

framework, but not execution model

• Consider spiral as execution model within

that guiding framework

• Planned with versions in mind

– incremental

• Each increment involves many cycles of

all the activities, ending with executable application

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Iterative & Incremental Dev.

Waterfall Spiral Iterative & Incremental Development

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Advantages & Disadvantages of IID

• Provides good opportunity to analyze risk
• System evolves
• Coding starts early
• Integration start sooner
• May still be ceremonial
• Iteration may be too long
• Some companies that claim to be doing

IID actually are doing waterfall

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Agile Development Process

• Iterative and evolutionary development
• Adaptive planning
• Incremental delivery
• Agility
• More focused on success than sticking

with a plan

• Working software is valued and

considered measure of progress

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Advantages

• Closely matches user expectations
• You may modify and evolve as

understanding as requirements evolve

• Functionality stabilizes overtime

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Disadvantage

• Hard to document each step
• Project management is not easy
• System may be poorly structure

– You may hack your way though

• Works effectively only for small teams

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Where does it work?

• For small teams
• Small to medium size projects
• Not effective on large projects

– (large projects are not effective any ways!!)

• Requires competent team

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The Agile Manifesto

• Individuals and interactions

– over process and tools

• Working Software

– over comprehensive documentation

• Customer collaboration

– over contract negotiations

• Responding to change

– over following a plan

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The Agile Principles

• Satisfy Customer through early and continuous delivery
• f valuable software
• Welcome changing requirements any time
• Deliver working software frequently
• Business people and developers work closely
• Motivated individuals trusted to do job
• Face-to-face conversation
• Working software measure of progress
• Processes that promote sustainable development
• Sponsors, developers, users should maintain constant

pace indefinitely

• Attention to technical excellence and good design

enhances agility

• Simplicity is essential
• Reflect on how to become more effective, and tunes

and adjusts behavior accordingly

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Agile Modeling

• UML is for understanding/communication not for

documentation

• Agile modeling is not avoiding modeling
• Do not apply UML to all or most of software
• Defer simpler design till programming
• Use UML for smaller percentage of system where it is

required

• Choose lightweight simpler tools
• Don’t model alone
• Look for good enough solution
• Use design as guidelines – it will be inaccurate when

you start

• Do not expect (or be expected) to design and hand off

for coding – developer must be part of designing

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Agile Processes

• Scrum

– Self-organizing teams – Daily team measurement – Avoid following predefined steps – Standup meetings, 30 day iteration, demo to stake holders at end of iteration

• XP

– Collaboration – Quick and early software creation – Communication, simplicity, feedback, courage – Constant feedback, test driven development