Lecture 3

Enterprise

Systems

Development(CSC447)

COMSATS Islamabad

Muhammad Usman, Assistant Professor

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Agile Development

2001: Kent Beck and 16 other software developers, referred to as “Agile Alliance”, signed the “manifesto for Agile software development”. It stated:

Through this work we have come to Value:

Individuals and interaction over processes and toolWorking software over comprehensive documentationCustomer collaboration over contract negotiationResponding to change over following plan

That is, while there is value in the items on the right , we values the items on the left more.

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Agile Methods Agile software development is a group of software

development methodologies that are based on similar principles.

Agile methodologies generally promote a project management process that encourages – frequent inspection and adaptation – a leadership philosophy that encourages team

work – a set of engineering best practices that allow for

rapid delivery of high-quality software, and a business approach that aligns development with customer needs and company goals

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What are Agile Methods? Agile software development is a conceptual

framework for undertaking software engineering projects.

Most agile methods attempt to minimize risk by developing software in short timeboxes, called iterations, which may typically last one to four weeks.

Each iteration is like a miniature software project of its own, and includes all of the tasks necessary to release the mini-increment of new functionality.

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Agile Methods v/s Traditional Methods

Agile methods emphasize real time communication, preferably face-to-face, over written documents.

Agile methods like XP relies on the close collaboration of activity engaged individuals with ordinary talents and has the ability to flexibly schedule the implementation of functionality, responding to changing business needs. Reference: Extreme Programming explained:

Embrace Change By: Kent Beck with Cynthia Andres; 2nd ed., 2005

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Different Agile Methods?

• Extreme Programming (XP) • Scrum• Agile Modeling• Adaptive Software Development (ASD)• Crystal Clear and Other Crystal Methodologies• Dynamic Systems Development Method (DSDM) • Feature Driven Development• Lean software development • Agile Unified Process (AUP)

Extreme Programming

• Emphasis on four characteristics of agility– Communication: continual interchange between

customers and developers– Simplicity: select the simplest design or

implementation– Courage: commitment to delivering functionality early

and often– Feedback: loops built into the various activitites during

the development process

eXtreme Programming (XP)

• Philosophy– Take known good practices and push them to

extremes• For example

– “If code reviews are good, we’ll review code all the time”

– “If testing is good, we’ll test all the time”– “If design is good, we’ll make it part of everybody’s

daily business”

eXtreme Programming (XP)

Essence of XP

• Four variables in software development : – Cost, Time, Quality, Scope

• Four Values– Communication, Simplicity, Feedback, and Courage

• Five Principles– Provide feedback, assume simplicity, make incremental changes,

embrace change, quality work

• 12 Practices

Twelve Facets of XP

• The planning game (customer defines value)

• Small releases• Metaphor (common vision,

common names)

• Simple design• Writing tests first• Refactoring

• Pair programming• Collective ownership• Continuous integration

(small increments)

• Sustainable pace (40 hours/week)

• On-site customer• Coding standards

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XP (Extreme Programming)XP Practices

– Planning game - programmers estimate effort of implementing customer stories and customer decides about scope and timing of releases

– Short releases - new release every 2-3 months

– Simple design - emphasis on simplest design

– Testing - development test driven…*

– Refactoring - restructuring and changes to simplify

– Pair Programming - 2 people at 1 computer

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XP (Extreme Programming)…….

XP Practices– Collective ownership - anyone can change any part

of the code at any time.– Continuous integration - new builds as soon as

code ready– 40 hour week - maximum 40-hour week. No

overtime– On-site customer - customer present and available

full-time for team– Coding standards - rules exist and are followed– Open workspace - large room small cubicles– Just rules - team has own rules but can be changed

any at time

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Planning– User stories are written.– Release planning creates the schedule.– Make frequent small releases– The Project Velocity is measured.– The project is divided into iterations.– Iteration planning starts each iteration.– Move people around.– A stand-up meeting starts each day.– Fix XP when it breaks.

Designing Simplicity. Choose a system metaphor. (system of names for your objects

that everyone can relate to) Use CRC cards for design sessions. Create spike solutions to reduce risk. Refactor whenever and wherever possible.

Key Practices…..

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Coding– The customer is always available.– Code must be written to agreed standards.– Code the unit test first.– All production code is pair programmed.– Only one pair integrates code at a time.– Integrate often.– No overtime.

Testing All code must have unit tests. All code must pass all unit tests before it can be released. When a bug is found tests are created. Acceptance tests are run often and the score is published.

Key Practices

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XP > Practices > “Circles of Life”On-site Customer

ReleasePlanning

Small Releases

AcceptanceTests Pair ProgrammingUnit Tests

Refactoring

Simple Design

CodingStandards

CollectiveOwnershipContinuousIntegration

Metaphor

SustainablePaceSynergy >

Customer – Team – Developer Pair – Team – Customer

When is Extreme Too Extreme?

• Extreme programming's practices are interdependent – A vulnerability if one of them is modified

• Requirements expressed as a set of test cases must be passed by the software– System passes the tests but is not what the customer is

paying for• Refactoring issue

– Difficult to rework a system without degrading its architecture

Scrum

• In Rugby, a scrum is a way to restart the game after an interruption, e.g. after a minor foul.

• “During a Scrum, the pack must work as a unit, not as 8 individuals. Everybody has a role to play. The important goal to bear in mind is that when you work well together as a unit, the whole is much greater than the sum of the parts.”

The On-Line Rugby Coaching Manual

What is Scrum?

• Scrum is not an acronym• Scrum is

– a team-based approach– to iteratively, incrementally develop systems and

products– when requirements are rapidly changing

• Assumes complicated, unpredictable environment• It produces a potentially shippable set of functionality at

the end of every iteration

How does Scrum work?

• Small teams (< 10 people)• A series of Sprints (1-4 weeks)• Visible, usable increments• Time-boxed

How does Scrum work?

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Sprint Rules

• Total focus—no unwanted diversion

• NO interruptions/changes from the outside

• New work may be uncovered by the team

• Very XP-ish

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What Happens During a Sprint?

• Frequent, short Scrum Meetings

• Each team produces a visible, usable increment

• Each increment builds on prior increments

• Clearly defined deliverables and responsibilities

• Each team member buys into the assignment

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What’s a Scrum Meeting?

• Short (15 - 30 min) frequent meetings, facilitated by the ScrumMaster

• All team members attend—even teleworkers

• One activity -- ScrumMaster asks each attendee 3 questions

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What Are The 3 Questions?

1. What have you completed (relative to the Backlog) since the last Scrum meeting?

2. What got in your way of completing this work?

3. What will you do between now and the next Scrum meeting?

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At the End of a Sprint?

• Status meeting with all stakeholders. • Increments are delivered.• Surprises are reported.• ANYTHING can be changed, work can be added, eliminated,

re-prioritized.• New estimates and team assignments are made for the next

Sprint.• The project can be cancelled.

“Experience from earlier increments allows better estimates and planning as project progresses. It's always easier to estimate shorter development periods”

Rational Unified Process

• S/W Engineering Process• Process Framework• Process Product• Workers, Activities, Artifacts, Workflows

RUP Phases

inc. elaboration construction transition

iteration phase

development cycle

release

A stable executable subset of the final product. The end of each iteration is a minor release.

increment

The difference (delta) between the releases of 2 subsequent iterations.

final production release

At this point, the system is released for production use.

milestone

An iteration end-point when some significant decision or evaluation occurs.

The Architecture of RUP

You Didn’t Understand the RUP When…

• You think that– Inception = requirements– elaboration = design– construction = implementation.

• You think that the purpose of elaboration is to fully and carefully define models, which are translated into code during construction

• You think that only prototypes are created in elaboration• You try to define most of the requirements before starting design or

implementation.• You try to define most of the design before starting implementation• A “long time” is spent doing requirements or design work before

programming starts• You try to plan a project in detail from start to finish, allocating the work

to each iteration; you try to speculatively predict all the iterations• An organization wants believable plans and estimates for projects before

they have entered the elaboration phase

RUP Support

• Templates– http://

sce.uhcl.edu/helm/rationalunifiedprocess/process/templates.htm

– http://pic.dhe.ibm.com/infocenter/reqpro/v7r1m0/index.jsp?topic=/com.ibm.reqpro.help/administering/projects/creating_modifying/r_rup_proj_template.html

• Tools– http://

www.rational.com.ar/tools/herramientas.html

S/W Development Best Practices

• Develop software iteratively• Manage requirements• Use component based architecture• Visually model software• Continuously verify software quality ?• Control changes to software

Process Models

• Waterfall• Prototyping• RAD• Incremental• Spiral• Agile

– XP– SCRUM

• RUP