CS 564AR © 2005 Prof. Bernstein CS 564AR Lecture 12 Agile software development

CS 564AR © 2005 Prof. Bernstein

CS 564AR

Lecture 12 Agile software development


Have you ever been on a project…

• With a reviewed & accepted requirements document (RARD) yet the project failed anyway?

• With a RARD and the developers did something else anyway?

• With a RARD and the stakeholders didn’t like what was delivered?

• Without a RARD, yet you still delivered working software which your stakeholders liked?


Agile Requirements Scope

Because of the changing environment, it is impossible to arrive at a stable, consistent set of system requirements before development starts.


Agile development focus

• Short Schedules• Fast Response to market• Rapid delivery of essential functionality

with acceptably lower quality.• Leverages UML Models


Enter the Traditional Business AnalystA Communication Facilitator Between Stakeholders and Developers

Requirements Specifications

QuestionsQuestions’


Agile Customer Relationship

Requirements

Questions

Customer teaming doubles development productivity


Agile Software Development

• People oriented• Highly collaborative• Handles changes smoothly• Focuses on MOV• Results in the creation of working software

systems that meets the highest-priority needs of stakeholders


Agile Values (www.agilealliance.org)Some Things Are More Important than Others

Emphasis on:1. Individuals and

interactions 2. Working software3. Customer

collaboration4. Responding to

change

Not on:

1. Processes and tools

2. Comprehensive documentation

3. Contract negotiation

4. Following a plan

http://www.agilealliance.org/


Agile PrinciplesBringing Focus to the Values

1. High priority on customer satisfaction (meet customer needs) through early and continuous delivery of valuable software.

2. Welcome changing requirements, even late in development. Agile processes harness change for the customer's competitive advantage.

3. Deliver working software frequently, from a couple of weeks to a couple of months, with a preference to the shorter timescale.

4. Business people and developers must work together daily throughout the project. 5. Build projects around motivated individuals. Give them the environment and support

they need, and trust them to get the job done. 6. The most efficient and effective method of conveying information to and within a

development team is face-to-face conversation. 7. Working software is the primary measure of progress. 8. Agile processes promote sustainable development. The sponsors, developers, and

users should be able to maintain a constant pace indefinitely. 9. Continuous attention to technical excellence and good design enhances agility. 10. Simplicity--the art of maximizing the amount of work not done--is essential. 11. The best architectures, requirements, and designs emerge from self-organizing teams. 12. At regular intervals, the team reflects on how to become more effective, then tunes

and adjusts its behavior accordingly.


Communication ModesAlways Strive to Use the Most Effective Approach

Co

mm

un

ica

tio

n E

ffe

cti

ven

es

s

Richness of Communication ChannelCold Hot

Paper

Audiotape

Videotape

Emailconversation

Phoneconversation

Videoconversation

Face-to-faceconversation

Face-to-faceat whiteboard

DocumentationOptions

ModelingOptions

Prototype Demonstrations


Misunderstandings about AgilityDon’t Be Fooled by Misinformation

• Misinformation by FUDers• Agile = “code and fix”• XP is the only agile process• Agilists don’t document• Agilists don’t model• An ISO/CMM/6sigma can’t be agile• Agile results in poor unacceptable quality• Agile doesn’t scale• Agilists ignore enterprise concerns

FUD = Fear, Uncertainty and Doubt


Agile Software Requirements ManagementChanging Requirements Are a Competitive Advantage if You Can Act on Them: www.agilemodeling.com/essays/agileRequirements.htm

{Each iteration implement the highest-priority requirements

Each new requirement is prioritized and added to the stack

Requirements may be reprioritized at any time

Requirements may be removed at any time

Requirements

HighPriority

LowPriority

http://www.agilemodeling.com/essays/agileRequirements.htm


Effectiveness of Requirements Gathering Techniques

Active Stakeholder Participation

On-Site Customer

Joint Application Design (JAD)

Legacy Code Analysis

Focus Groups

Electronic Interviews

Reading

CollaborativeInteraction

Restricted Interaction

One-On-One Interviews Observation

Teaming Contract Enforcement


Tests as Primary ArtifactsReduce Documentation by Single Sourcing Information

• Acceptance tests are considered to be primary requirements artifacts• You can reduce your requirements documentation

dramatically by not recording the same information twice

• Unit tests are considered to be detailed design artifacts• You can reduce your design documentation

dramatically and increase the chance that your detailed design artifacts are kept up to date by coders in the code commentary

• www.agilemodeling.com/essays/singleSourceInformation.htm

http://www.agilemodeling.com/essays/singleSourceInformation.htm


Regular Deployment of Working SoftwareYou Want to Decrease the Feedback Cycle

• Too many projects…• are “90% complete” for months• Deliver wonderful plans but no software• Deliver wonderful prototypes, but no production

software• The only accurate measure of software

development progress is the delivery of software• Deliver something at the end of each cycle/iteration• Iterations should be short• At all points in time stakeholders can see what

they’ve gotten for their investment to date• Measure component deliveries to test teams


Follow Guidance

• Guidance = Standards and guidelines• Agile developers prefer to develop high-

quality artifacts, and that includes ensuring that they are developed in a consistent manner

• XP practice Coding Standards• AM practice Modeling Standards• www.agilemodeling.com/style/

http://www.agilemodeling.com/style/


What Are Agile Models?

• Agile models:• Fulfill their purpose• Are understandable• Are sufficiently accurate• Are sufficiently consistent• Are sufficiently detailed• Provide positive value• Are as simple as possible, but

no simpler

• “Agile models are just barely enough!” Scott Ambler Dynamic Range

Ideal

Discrete Specifications

AgileRequirements


Agile Model Driven Development (AMDD)Project Level (www.agilemodeling.com/essays/amdd.htm)

Cycle n: Development

Cycle 2: Development

Cycle 1: Development

Cycle 0: Initial Modeling

Initial RequirementsModeling

(days)

Initial ArchitecturalModeling

(days)

ModelStorming(minutes)

Implementation(Ideally Test Driven)

(hours)

Reviews(optional)

All Cycles(hours)

Goals: Gain an initial understanding of the scope, the business domain, and your overall approach.

Goal: Quickly explore in detail a specific issue before you implement it.

Goal: Develop working software in an evolutionary manner.

http://www.agilemodeling.com/essays/amdd.htm


Agile Documentation

• Far less than ‘pseudo developers’ insist• Agile documents:

• Maximize stakeholder investment • Are concise• Fulfill a purpose • Describe information that is less likely to change • Describe “good things to know”• Have a specific customer and facilitate the work efforts of that

customer • Are sufficiently accurate, consistent, and detailed • Are sufficiently indexed

• www.agilemodeling.com/essays/agileDocumentation.htm

http://www.agilemodeling.com/essays/agileDocumentation.htm

http://www.agilemodeling.com/essays/agileDocumentation.htm


Serial Cost-Benefit CurveA Large Up Front Investment Pushes Your Break-Even Point Out

Value

Time

ReleaseT= 16

months

Break Even PointT= 26 months


Incremental Cost Benefit CurveDeveloping Incrementally Reduces Time to Break Even

Value

Time

R1T= 8

months

Break Even PointT= 14 months

R2T= 12

months

R3T= 16

months


Agile Cost of Change CurveAgilists Find Ways to Decrease the Feedback Cycle

Cost ofChange

Time


Characteristics of Agile Application Development processes

• The processes of specification, design and implementation are concurrent. There is no detailed specification and design documentation is minimized.

• The system is developed in a series of increments. End users evaluate each increment and make proposals for later increments.

• System user interfaces are usually developed using an interactive development system.


An iterative development process

Define system deliverables

Integrate increment

Define system deliverables

Specify system increment

Build systemincrement

Validate increment

Validate systemDone?

No

Deliver systemYes


Advantages of incremental development

• Accelerated delivery of customer services. Each increment delivers the highest priority functionality to the customer.

• User engagement with the system. Users have to be involved in the development which means the system is more likely to meet their requirements and the users are more committed to the system.


Challenges of Agile Development Requirements

• How do you capture sufficient requirements to make developers productive without burying them in documentation?

• How do you provide designers with requirements early enough to impact design, without delaying implementation?

• What techniques can we use to prioritize requirements so we can fulfill the right mix of strategic, tactical and operational priorities?

• Can light methods incorporate all the needed requirements, specification and design efforts without becoming heavy and slow?


Problems with incremental development

• Management problems • Progress can be hard to judge and problems hard to find because

there is no documentation to demonstrate what has been done.• Contractual problems

• The normal contract may include a specification; without a specification, different forms of contract have to be used.

• Validation problems• Without a specification, what is the system being tested against?

• Maintenance problems• Continual change tends to corrupt software structure making it

more expensive to change and evolve to meet new requirements.


Management decisions ofagile development

• What are the key criteria that support effective decision making?

• What untapped sources of information can be leveraged to shed new light on the problem?

• What are the organizational processes that lead to decisions, and how can they be optimized?

• Who are the players that need to be involved in the decision making process?

• To what extent can decisions be automated, and where do people need to step in to make judgment calls?


Technologies used in Agile Development

• Prototyping

• .NET and J2EE

• Web Design

• Visual Basic

• Databases


Prototyping

• For some large systems, incremental iterative development and delivery may be impractical; this is especially true when multiple teams are working on different sites.

• Prototyping, where an experimental system is developed as a basis for formulating the requirements may be used. This system is thrown away when the system specification has been agreed.


Incremental development and prototyping

Incrementaldevelopment

Throwawayprototyping

Delivered system

Executable prototype + System specification

Outlinerequirement


Conflicting objectives

• The objective of incremental development is to deliver a working system to end-users. The development starts with those requirements which are best understood.

• The objective of throw-away prototyping is to validate or derive the system requirements. The prototyping process starts with those requirements which are poorly understood.


Agile methods

• Dissatisfaction with the overheads involved in design methods led to the creation of agile methods. These methods:Focus on the code rather than the design;Are based on an iterative approach to software

development;Are intended to deliver working software quickly and

evolve this quickly to meet changing requirements.

• Agile methods are probably best suited to small/medium-sized business systems or PC products.


Principles of agile methods

Principle Description

Customer involvement The customer should be closely involved throughout the development process. Their role is provide and prioritize new system requirements and to evaluate the iterations of the system.

Incremental delivery The software is developed in increments with the customer specifying the requirements to be included in each increment.

People not process The skills of the development team should be recognized and exploited. The team should be left to develop their own ways of working without prescriptive processes.

Embrace change Expect the system requirements to change and design the system so that it can accommodate these changes.

Maintain simplicity Focus on simplicity in both the software being developed and in the development process used. Wherever possible, actively work to eliminate complexity from the system.


Problems with agile methods

• It can be difficult to keep the interest of customers who are involved in the process.

• Team members may be unsuited to the intense involvement that characterises agile methods.

• Prioritising changes can be difficult where there are multiple stakeholders.

• Maintaining simplicity requires extra work.• Contracts may be a problem as with other

approaches to iterative development.


Extreme programming

• Perhaps the best-known and most widely used agile method.

• Extreme Programming (XP) takes an ‘extreme’ approach to iterative development. New versions may be built several times per

day;Increments are delivered to customers every 2

weeks;All tests must be run for every build and the

build is only accepted if tests run successfully.


The XP release cycle

Break downstories to tasks

Select userstories for this

releasePlan release

Releasesoftware

Evaluatesystem

Develop/integratetest software


Extreme programming practices

Incremental planning Requirements are recorded on Story Cards and the Stories to beincluded in a release are determined by the time available andtheir relative priority. The developers break these Stories intodevelopment ŌTasksÕ.

Small Releases The minimal useful set of functionality that provides businessvalue is developed first. Releases of the system are frequent andincrementally add functionality to the first release.

Simple Design Enough design is carried out to meet the current requirementsand no more.

Test first development An automated unit test framework is used to write tests for a newpiece of functionality before that functionality itself isimplemented.

Refactoring Elimination of redundant features and class generalization.

.


Extreme programming practices

Pair Programming Developers work in pairs, checking each otherÕs work andproviding the support to always do a good job.

Collective Ownership The pairs of developers work on all areas of the system, so thatno islands of expertise develop and all the developers own all thecode. Anyone can change anything.

Continuous Integration As soon as work on a task is complete it is integrated into thewhole system. After any such integration, all the unit tests in thesystem must pass.

Sustainable pace Large amounts of over-time are not considered acceptable as thenet effect is often to reduce code quality and medium termproductivity

On-site Customer A representative of the end-user of the system (the Customer)should be available full time for the use of the XP team. In anextreme programming process, the customer is a member of thedevelopment team and is responsible for bringing systemrequirements to the team for implementation.


Requirements scenarios

• XP requirements are expressed as scenarios or user stories.

• Written on cards and assigned to implementation tasks. These tasks are the basis of schedule and cost estimates.

• The customer chooses the stories for inclusion in the next release based on priorities and the schedule estimates.


Story card for document downloading

Downloading and printing an article

First, you select the article that you want from a displayed list. Youthen have to tell the system how you will pay for it - this can eitherbe through a subscription, through a company account or by creditcard.

After this, you get a copyright form from the system to fill in and,when you have submitted this, the article you want is downloadedonto your computer.

You then choose a printer and a copy of the article is printed. Youtell the system if printing has been successful.

If the article is a print-only article, you canÕt keep the PDF versionso it is automatically deleted from your computer.


XP and change

• Conventional wisdom in software engineering is to design for change. It is worth spending time and effort anticipating changes as this reduces costs later in the life cycle.

• XP, however, maintains that this is not worthwhile as changes cannot be reliably anticipated.Rather, it proposes constant code improvement (refactoring) to make changes easier when they have to be implemented.


Testing in XP

• Test-first development.

• Incremental test development from scenarios.

• User involvement in test development and validation.

• Automated test harnesses are used to run all component tests each time that a new release is built.


Task cards for document downloading

Task 1: Implement principal workflow

Task 2: Implement article catalog and selection

Task 3: Implement payment collection

Payment may be made in 3 different ways. The userselects which way they wish to pay. If the userhas a library subscription, then they can input thesubscriber key which should be checked by thesystem. Alternatively, they can input an organisationalaccount number. If this is valid, a debit of the costof the article is posted to this account. Finally, theymay input a 16 digit credit card number and expirydate. This should be checked for validity and, ifvalid a debit is posted to that credit card account.


Test case description

Test 4: Test credit card validity

Input:A string representing the credit card number and two integers representingthe month and year when the card expiresTests:Check that all bytes in the string are digitsCheck that the month lies between 1 and 12 and theyear is greater than or equal to the current year.Using the first 4 digits of the credit card number,check that the card issuer is valid by looking up thecard issuer table. Check credit card validity by submitting the cardnumber and expiry date information to the cardissuerOutput:OK or error message indicating that the card is invalid


Test-first development

• Writing tests before code clarifies the requirements to be implemented.

• Tests are written as programs rather than data so that they can be executed automatically. The test includes a check that it has executed correctly.

• All previous and new tests are automatically run when new functionality is added. Thus checking that the new functionality has not introduced errors.


Pair programming

• In XP, programmers work in pairs, sitting together to develop code.

• This helps develop common ownership of code and spreads knowledge across the team.

• It serves as an informal review process as each line of code is looked at by more than 1 person.

• It encourages refactoring as the whole team can benefit from this.

• Development productivity is similar to two people working independently.


Rapid application development

• Agile methods have received a lot of attention but other approaches to rapid application development have been used for many years.

• These are designed to develop data-intensive business applications and rely on programming and presenting information from a database.


Agile development environment tools

• Database programming language

• Interface generator

• Links to office applications

• Report generators


An agile application development environment

DBprogramming

language

Interfacegenerator

Officesystems

Reportgenerator

Database management system

Rapid applicationdevelopment environment


Interface generation

• Many applications are based around complex forms and developing these forms manually is a time-consuming activity.

• RAD environments include support for screen generation including: Interactive form definition using drag and drop

techniques;Form linking where the sequence of forms to be

presented is specified;Form verification where allowed ranges in form

fields is defined.


Visual programming

• Scripting languages such as Visual Basic support visual programming where the prototype is developed by creating a user interface from standard items and associating components with these items

• A large library of components exists to support this type of development

• These may be tailored to suit the specific application requirements


Problems with visual development

• Difficult to coordinate team-based development.

• No explicit system architecture.

• Complex dependencies between parts of the program can cause maintainability problems.


COTS reuse

• An effective approach to rapid development is to configure and link existing off the shelf systems.

• For example, a requirements management system could be built by using:A database to store requirements;A word processor to capture requirements and

format reports;A traceability management spreadsheet


Compound documents

• For some applications, a prototype can be created by developing a compound document.

• This is a document with active elements (such as a spreadsheet) that allow user computations.

• Each active element has an associated application which is invoked when that element is selected.

• The document itself is the integrator for the different applications.


Software prototyping

• A prototype is an initial version of a system used to demonstrate concepts and try out design options.

• A prototype can be used in:The requirements engineering process to help

with requirements elicitation and validation;In design processes to explore options and

develop a UI design;In the testing process to run back-to-back

tests.


Benefits of prototyping

• Improved system usability.

• A closer match to users’ real needs.

• Improved design quality.

• Improved maintainability.

• Reduced development effort.


Back to back testing

Test data

Resultscomparator

Systemprototype

Applicationsystem

Differencereport


The prototyping process

Establishprototypeobjectives

Defineprototype

functionality

Developprototype

Evaluateprototype

Prototypingplan

Outlinedefinition

Executableprototype

Evaluationreport


Throw-away prototypes

• Prototypes should be discarded after development as they are not a good basis for a production system:• It may be impossible to tune the system to

meet non-functional requirements;• Prototypes are normally undocumented;• The prototype structure is usually

degraded through rapid change;• The prototype probably will not meet

normal organisational quality standards.


Agile Challenges• How do you capture sufficient requirements to make

developers productive without burying them in documentation?

• How do you provide designers with requirements early enough to impact design, without delaying implementation?

• What techniques can we use to prioritize requirements so we can fulfill the right mix of strategic, tactical and operational priorities?

• Can light methods incorporate all the needed requirements, specification and design efforts without becoming bureaucratic?


Acknowledgement

• Thanks to Scott W Ambler who provided much of this material and spearheads the professional and trade literature making Agile ligitimate.

• Visit Scott’s and Software Develpment web sites:

http://www.agilemodeling.com/

http://www.ambysoft.com/scottAmbler.htm

http://www.sdmagazine.com/

http://www.agilemodeling.com/

http://www.ambysoft.com/scottAmbler.htm


References

• http://www.agilemodeling.com/essays/agileRequirements.htm

• http://www.agilemodeling.com/essays/agileRequirementsBestPractices.htm

• http://www.devx.com/DevX/Article/11801• http://en.wikipedia.org/wiki/

Agile_software_development• Agile Software Development, by

Alistair Cockburn



http://www.agilemodeling.com/essays/agileRequirementsBestPractices.htm

http://www.agilemodeling.com/essays/agileRequirementsBestPractices.htm

http://www.devx.com/DevX/Article/11801

http://www.amazon.com/exec/obidos/search-handle-url/index=books&field-author-exact=Alistair%20Cockburn&rank=-relevance%2C%2Bavailability%2C-daterank/102-9057094-0052126

Documents

CS 564AR © 2005 Prof. Bernstein CS 564AR Lecture 12 Agile software development