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CS 564AR Lecture 12 Agile software developmentCS 564AR © Prof. Bernstein
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? CS 564AR © Prof. Bernstein
Agile Requirements ScopeBecause of the changing environment, it is impossible to arrive at a stable, consistent set of system requirements before development starts. CS 564AR © Prof. Bernstein
Agile development focusShort Schedules Fast Response to market Rapid delivery of essential functionality with acceptably lower quality. Leverages UML Models CS 564AR © Prof. Bernstein
Enter the Traditional Business Analyst A Communication Facilitator Between Stakeholders and Developers Questions’ CS 564AR © Prof. Bernstein
Agile Customer RelationshipCustomer teaming doubles development productivity CS 564AR © Prof. Bernstein
Agile Software DevelopmentPeople 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 CS 564AR © Prof. Bernstein
Individuals and interactions Working software Customer collaboration Agile Values ( Some Things Are More Important than Others Emphasis on: Individuals and interactions Working software Customer collaboration Responding to change Not on: Processes and tools Comprehensive documentation Contract negotiation Following a plan CS 564AR © Prof. Bernstein
Agile Principles Bringing Focus to the ValuesHigh priority on customer satisfaction (meet customer needs) through early and continuous delivery of valuable software. Welcome changing requirements, even late in development. Agile processes harness change for the customer's competitive advantage. Deliver working software frequently, from a couple of weeks to a couple of months, with a preference to the shorter timescale. Business people and developers must work together daily throughout the project. Build projects around motivated individuals. Give them the environment and support they need, and trust them to get the job done. The most efficient and effective method of conveying information to and within a development team is face-to-face conversation. Working software is the primary measure of progress. Agile processes promote sustainable development. The sponsors, developers, and users should be able to maintain a constant pace indefinitely. Continuous attention to technical excellence and good design enhances agility. Simplicity--the art of maximizing the amount of work not done--is essential. The best architectures, requirements, and designs emerge from self-organizing teams. At regular intervals, the team reflects on how to become more effective, then tunes and adjusts its behavior accordingly. CS 564AR © Prof. Bernstein
Communication Modes Always Strive to Use the Most Effective ApproachPrototype Demonstrations CS 564AR © Prof. Bernstein
Misunderstandings about Agility Don’t Be Fooled by MisinformationMisinformation 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 CS 564AR © Prof. Bernstein
Agile Software Requirements Management Changing Requirements Are a Competitive Advantage if You Can Act on Them: CS 564AR © Prof. Bernstein
Effectiveness of Requirements Gathering TechniquesTeaming Contract Enforcement CS 564AR © Prof. Bernstein
Tests as Primary Artifacts Reduce Documentation by Single Sourcing InformationAcceptance 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 CS 564AR © Prof. Bernstein
Regular Deployment of Working Software You Want to Decrease the Feedback CycleToo 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 CS 564AR © Prof. Bernstein
Guidance = Standards and guidelines 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 CS 564AR © Prof. Bernstein
What Are Agile Models? Discrete Specifications Agile models: IdealFulfill 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 Ideal Agile Requirements Dynamic Range CS 564AR © Prof. Bernstein
Agile Model Driven Development (AMDD) Project Level (www.agilemodeling.com/essays/amdd.htm)CS 564AR © Prof. Bernstein
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 CS 564AR © Prof. Bernstein
Serial Cost-Benefit Curve A Large Up Front Investment Pushes Your Break-Even Point OutCS 564AR © Prof. Bernstein
Incremental Cost Benefit Curve Developing Incrementally Reduces Time to Break EvenCS 564AR © Prof. Bernstein
Agile Cost of Change Curve Agilists Find Ways to Decrease the Feedback CycleCS 564AR © Prof. Bernstein
Characteristics of Agile Application Development processesThe 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. CS 564AR © Prof. Bernstein
An iterative development processDefine system deliverables Define system deliverables Specify system increment Build system increment Validate increment No Validate system Integrate increment Yes Deliver system Done? CS 564AR © Prof. Bernstein
Advantages of incremental developmentAccelerated 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. CS 564AR © Prof. Bernstein
Challenges of Agile Development RequirementsHow 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? CS 564AR © Prof. Bernstein
Problems with incremental developmentManagement 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. CS 564AR © Prof. Bernstein
Management decisions of agile developmentWhat 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? CS 564AR © Prof. Bernstein
Technologies used in Agile DevelopmentPrototyping .NET and J2EE Web Design Visual Basic Databases CS 564AR © Prof. Bernstein
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. CS 564AR © Prof. Bernstein
Incremental development and prototypingDeli v er ed system development Outline requirement Throwaway Ex ecuta b le prototype + prototyping System specification CS 564AR © Prof. Bernstein
Conflicting objectivesThe 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. CS 564AR © Prof. Bernstein
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. CS 564AR © Prof. Bernstein
Principles of agile methodsDescription 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 so ftware 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 o f 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 deve lopment process used. Wherever possible, actively work to eliminate complexity from the system. CS 564AR © Prof. Bernstein
Problems with agile methodsIt 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. CS 564AR © Prof. Bernstein
Perhaps the best-known and most widely used agile method. 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. CS 564AR © Prof. Bernstein
The XP release cycle Select user Break down stories for thisPlan release stories to tasks release Evaluate Release Develop/integrate system software test software CS 564AR © Prof. Bernstein
Extreme programming practicesncr em en t a l p l ann i ng R e qui r e m en ts a r e r e cord e d on S t o r y C a r ds and t he St or i e s t o be i nc l uded i n a r e l e as e a r e de t er mi ned by t h e tim e a va il ab l e a nd t he ir r e l a ti ve pr i o rit y. The deve l ope r s br e ak t he s e S t o ri es i n t o deve l op m en t Ō T a s ks Õ . Sm a ll R e l eas e s T he mi n im a l u s e f u l s e t o f f unc ti ona lit y t ha t prov i de s bu si nes s va l ue i s deve l oped f ir s t. R el eas e s of t he s ys t e m a r e fr equen t and i nc r e m en t a ll y a dd f unc ti ona lit y t o t h e fi r st r e l ea s e. Sim pl e De si gn E nough de si gn i s ca rri ed ou t to m ee t t he cu rr en t r equ ir e m en t s and no m o r e. T es t f ir s t deve l op m en t An au t o m a t ed un it t es t f r a m ewo r k is u s ed t o w r i te t e s t s f o r a new p i ece o f f unc ti ona lit y be f o r e t ha t fun ct ion a l it y it se lf is im p l e m en t ed . R e fa c to ri ng Elimination of redundant features and class generalization. . CS 564AR © Prof. Bernstein
Extreme programming practicesir Pr ogra mmi ng Deve l op e r s wo r k i n pa ir s , che c king ea c h o t he r Õ s w ork and p r ov i ding t he suppo rt t o a l w ays do a good j ob . Co ll e c t i ve Owne rs hip T he pa ir s o f deve l op e r s wo r k on a ll a re a s of t he s ys t e m, s o t ha t no i sl ands o f expe rti s e deve l op and al l t he deve l ope r s own a ll t he code . Anyon e c a n chang e any t h i ng . Con ti nuou s I n t egr at ion A s s oon a s wo r k on a t ask i s co m pl et e it i s i n t eg r a t ed i n t o t he who l e sy st e m . Af t e r any s uch i n t eg r a ti on , a ll t h e un it t e st s i n t he sy st e m m u st pa s s . S us t a i nab le pac e L arg e a m oun ts o f ove r-t i me a r e not con s id e r e d ac c ep t ab l e a s t he ne t ef f ec t i s of t en t o r educ e code qua lit y a nd m ed i u m t e rm p r oduc ti v i ty On - s it e Cu s to m e r A rep r e s en t a ti ve of t he end - u s er o f t he sy s t em (t he C us t o m e r ) shou l d be ava il ab l e f u ll tim e fo r th e u s e o f t h e X P te a m . In an ex tr e m e prog r a mmi ng p r oce s s , t he cus t o m e r is a m e m be r o f th e deve l op m en t t ea m a nd i s r espon si b l e f or b ri nging sy st e m r equ i r e m e n t s to t he te a m f or im p l e m en t a ti on. CS 564AR © Prof. Bernstein
Requirements scenariosXP 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. CS 564AR © Prof. Bernstein
Story card for document downloadingDownloading and printing an article First, you select the article that you want from a displayed list. Y ou then have to tell the system how you will pay for it - this can either be through a subscription, through a company account or by credit card. After this, you get a copyright form from the system to fill in and, when you have submitted this, the article you want is downloaded onto your computer . Y ou then choose a printer and a copy of the article is printed. Y ou tell the system if printing has been successful. If the article is a print-only article, you canÕ t keep the PDF version so it is automatically deleted from your computer . CS 564AR © Prof. Bernstein
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. CS 564AR © Prof. Bernstein
Test-first development. Incremental test development from scenarios. 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. CS 564AR © Prof. Bernstein
Task cards for document downloadingask 1: Implement principal workflow T ask 2: Implement article catalog and selection T ask 3: Implement payment collection Payment may be made in 3 dif ferent ways. The user selects which way they wish to pay . If the user has a library subscription, then they can input the subscriber key which should be checked by the system. Alternatively , they can input an or ganisational account number . If this is valid, a debit of the cost of the article is posted to this account. Finally , they may input a 16 digit credit card number and expiry date. This should be checked for validity and, if valid a debit is posted to that credit card account. CS 564AR © Prof. Bernstein
Test case description T est 4: T est cr edit card validity Input: Astring representing the credit card number and two integers representing the month and year when the card expires T ests: Check that all bytes in the string are digits Check that the month lies between 1 and 12 and the year 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 the card issuer table. Check credit card validity by submitting the card number and expiry date information to the card issuer Output: OK or error message indicating that the card is invalid CS 564AR © Prof. Bernstein
Test-first developmentWriting 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. CS 564AR © Prof. Bernstein
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. CS 564AR © Prof. Bernstein
Rapid application developmentAgile 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. CS 564AR © Prof. Bernstein
Agile development environment toolsDatabase programming language Interface generator Links to office applications Report generators CS 564AR © Prof. Bernstein
An agile application development environmentInter face Office gener a tor systems DB R epor t prog ramming gener a tor langua ge Database management system Rapid application development environment CS 564AR © Prof. Bernstein
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. CS 564AR © Prof. Bernstein
These may be tailored to suit the specific application requirementsVisual 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 CS 564AR © Prof. Bernstein
Problems with visual developmentDifficult to coordinate team-based development. No explicit system architecture. Complex dependencies between parts of the program can cause maintainability problems. CS 564AR © Prof. Bernstein
For example, a requirements management system could be built by using: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 CS 564AR © Prof. Bernstein
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. CS 564AR © Prof. Bernstein
A prototype can be used in: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. CS 564AR © Prof. Bernstein
Benefits of prototypingImproved system usability. A closer match to users’ real needs. Improved design quality. Improved maintainability. Reduced development effort. CS 564AR © Prof. Bernstein
Back to back testing T est data S ystem Application prototype systemResults comparator Difference repor t CS 564AR © Prof. Bernstein
The prototyping processEsta b lish Define De v elop Ev alua te pr ototype prototype pr ototype pr ototype objecti v es functionality Pr ototyping Outline Ex ecuta b le Ev alua tion plan definition pr ototype r epor t CS 564AR © Prof. Bernstein
Throw-away prototypesPrototypes 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. CS 564AR © Prof. Bernstein
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? CS 564AR © Prof. Bernstein
Visit Scott’s and Software Develpment web sites: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: CS 564AR © Prof. Bernstein
Agile Software Development, by Alistair CockburnReferences Agile Software Development, by Alistair Cockburn CS 564AR © Prof. Bernstein
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