• 9.1 Agile Methods
  • 9.1.1 Prototyping
  • 9.1.2 Extreme Programming
  • 9.1.3 Scrum
    • The Scrum Team
    • Scrum Events
• 9.2 Agile team

9.1 Agile Methods

When using a heavy weight development method (such as RUP) it is difficult to change direction. Once the contract has been signed, the development team’s job is to deliver the functionality as laid down in the contract. If reality changes, or the user gets a different insight, such is difficult to accomplish.

Agile approaches to software development have a lot in common with the iterative development approaches. True agile methods assume change is inevitable. Their focus is to deliver value to the customer as quickly as possible, and not bother about plans and processes that won’t be followed anyway. The essence of agile methods is laid down in the Manifesto for Agile Software Development, published in 2001 by a group of well-known pioneers in this area (Beck et al., 2001). The key values of the agile movement are:

• Individuals and interactions over processes and tools.
• Working software over comprehensive documentation.
• Customer collaboration over contract negotiation.
• Responding to change over following a plan.

Agile methods involve the users in every step taken. The development cycles are small and incremental. The series of development cycles is not extensively planned in advance, but the new situation is reviewed at the end of each cycle. This includes some planning for the next cycle.

At the end of each cycle, the system is up and running. That is, there is a working system, one that delivers value to its users. This strongly resembles evolutionary prototyping as discussed in section 9.1.1 of this Unit. But the difference in wording does reflect quite a different attitude. The term prototyping suggests something intermediate, not yet final, temporary.

The Agile Manifesto doesn’t provide concrete steps. Agile movement include:

• Crystal Clear
• Extreme Programming (XP)
• Feature Driven Development (FDD)
• Dynamic Systems Development Method (DSDM)
• Scrum
• Test-driven development (TDD).

Agile methods do not have an extensive architectural or design phase. It is more effective to only do the design as far as needed for the immediate next step. Agile methods often have a separate activity to improve the design after each increment, known as refactoring (see Unit 7).

Agile methods emphasize the human factor in software development. Team spirit is considered very important. Often, an agile team occupies one big room. The users are on site as well. Agile methods have short communication cycles between developers and users, and between developers.

Also agile methods do not spend much efforts on documentation. If you have a question, ask one of your mates. Do not struggle with a large pile of paper, that quite likely will not provide the answer anyway.

9.1.1 Prototyping

It is often difficult to get and maintain a sufficiently accurate perception of the requirements of the prospective user. What is wanted instead of the present situation is often not easy to determine. This holds even more in cases where we are concerned with a new application and the customer does not know the full possibilities of automation. In such cases, the development of one or more prototypes may help.

In software development context a prototype can be described as a working model of (possibly parts of) a software system, which emphasizes certain aspects.

One of the main difficulties for users is to express their requirements precisely. It is natural to try to clarify these through prototyping. This can be achieved by developing the user interface quickly. The prospective user may then work with a system that contains the interaction component but not, or to a much lesser extent, the software that actually processes the input. In this way, the user may get a good impression of what the future system will provide him with, before large investments are made to realize the system. Prototyping thus becomes a tool for requirements engineering. This is illustrated graphically in figure 9.1.

This figure shows that the various phases are gone through in two ways. The left-hand side of the figure is concerned with the prototyping stages. The iteration corresponds to the user-validation process, whereby new or changed requirements trigger the next cycle. The right-hand side concerns the actual production of the operational system. The difference between the two branches is that, by using different techniques and tools, the left-hand side can be traversed much more quickly and against much lower costs.

In figure 9.1, the prototyping phases and the later production phases have been clearly separated. This is appropriate, since we will use different techniques during the actual production phase, put much more emphasis on documentation, and so on. It is even feasible not to carry over the software product from the prototyping phases to the actual production phase, but to explicitly throw it away after the prototyping phases have come to an end. This is known as throwaway prototyping. It is not necessary to do so, though. The prototype may evolve to the final product. The user starts by formulating the raw requirements, on the basis of which a first version of the system is produced. The user starts to work with this system, which leads to new, or changed, requirements. The next version is then developed. After a number of such iterations, the user is satisfied and the last version developed is the product to be delivered. This is known as evolutionary prototyping. In practice, evolutionary prototyping is used much more often than throwaway prototyping.

Users as well as developers are generally more positive about systems developed using a prototyping approach. This positive attitude concerns both the development process and the resulting product. Users feel more involved in the development process and have fewer conflicts with the designers. The extensive user involvement results in systems which better satisfy user needs.

As a consequence, the end result is a leaner system whose functionality closer matches the real user requirements. If users are shown a working system at an early stage and are given the opportunity to try it out, chances are that problems are detected at an early stage as well. This prevents a waste of manpower which would otherwise be needed to redo part of the work. If users are in a position to influence and modify the design, the system features will better reflect their requirements and the system will be easier to use.

The use of special-purpose prototyping tools or languages makes it easy to add features. Since the time interval between successive versions of the prototype is small, users may think that it is easy to realize new features and may specify additional requirements.

Prototyping involves iterative design steps and, because of the repeated attention to the design, its quality may increase. Since it is known a priori that the design will evolve during subsequent prototyping steps, greater attention will be given to quality factors such as flexibility and modularity and, as a result, design quality may improve as well.

On the other hand, prototyping generally does not enforce strict design and development standards. The chances are that documentation is sacrificed for speed. Because of additions resulting from frequent rework steps, the design quality of an evolutionary prototype may deteriorate. For that reason too, the resulting systems are less maintainable. Especially in evolutionary prototypes, the robustness of the system will often be less than is customary with a more traditional approach. In agile methods, refactoring is applied to counteract this phenomenon. Finally, performance tends to be worse because attention is focused on functionality and performance measures are either not taken at all or at a point in time at which they have become too difficult to realize.

It is generally felt that prototyping projects require an experienced team. Prototyping involves making far-reaching design decisions, especially during early iterations. In each iteration, user requests have to be weighed, both mutually and against the ease and cost of their realization. Inexperienced team members are more likely to make poor choices, thereby seriously threatening the success of a prototyping effort.

There are recommendations for the use of prototyping techniques:

• prototyping is particularly useful in situations where the user requirements are unclear or ambiguous;
• prototyping is also particularly useful for systems with a considerable emphasis on the user interface and which have a high degree of user interaction;
• users and designers must be well aware of the prototyping approach and its pitfalls;
• prototyping must also be planned and controlled. The limits must be imposed on the number of iterations. Explicit procedures for documenting and testing prototypes must be established.

By taking appropriate counter-measures, the potential disadvantages of prototyping can be guarded against. Prototyping is then a viable alternative process model for many a software development project.

9.1.2 Extreme Programming

Extreme Programming (XP) is a pure agile method. XP is a software development methodology which is intended to improve software quality and responsiveness to changing customer requirements.  It is based on a number of best practices that have been known for long. XP takes these practices to extreme levels.

For instance, we know that code reading by your pals, such as is done in walkthroughs and code inspections is a very effective test method. In XP, one does this all the time: two programmers work together behind one computer screen. One of them does the coding, the other one looks over her shoulder, gives advice, notices small slips, asks questions, and the like. They act as pilot and co-pilot. At any point in time, the roles may shift. This practice is called pair programming.

The full set of XP practices is given in figure 9.2. Typically, an XP team is not too big, and occupies one room. Planning meetings are very short, and involve the immediate functionality to be delivered to the customer. Planning involves both the customer and the technical people. The customer has to set priorities, determine dates of releases, and the like. The customer describes desirable features of the system in stories, on index cards. The technical people estimate how long it takes to implement a story, decide on the order in which stories within one release will be implemented, etc.

In XP, the design is kept as simple as possible. Since the future is, after all, unclear, there is no use to design a grand scheme that will not be followed anyhow. So the design only covers the current version of the system. After a task is accomplished, the system is checked to see how it can be improved (remove duplicate code, make it simpler, make it more flexible). This is called refactoring. This refactoring need not be restricted to one’s own code. Everyone is responsible for the whole system. To make this work, one needs to set coding standards.

When a team works on implementing a story, it writes tests to check the implementation of that story at the same time. Before the new code is checked in, all these tests have to run successfully. After the code has been checked in, the full test suite is run, and again all tests have to run successfully. If not, the new code is removed again to fix it. This way, there always is a running system.

XP is based on five principles that drive its practices:

• Rapid feedback - feedback is obtained quickly, within hours, or at most a few days. By testing each small piece added, developers immediately learn what works and what doesn’t. By frequently delivering a running system to the customer, the customer learns what value the system offers, and what next features are needed
• Assume simplicity - today’s job is done today, and tomorrows job is left for tomorrow. Don’t build in extra complexity so that a certain class becomes more flexible and may be reused if a certain feature is to be added. If and when this feature is needed, it will be added, and code will be refactored to make it simpler.
• Incremental change - in XP, things change in small increments. The plan changes a little at a time, the design changes a little, the team changes a little, etc.
• Embracing change - by not planning, designing, coding more than is needed right now, the most options for the future are kept. Only the most pressing problem is tackled today. The rest is left for tomorrow.
• Quality work - the team should find pride in delivering excellent quality.

As noted before in this chapter, agile methods are suited for certain projects, but not for all. This is certainly also true for XP, the most extreme agile approach. If requirements are unsure, the system is not too big, and the customer can be on site, XP deserves serious consideration. Early sources recommend using all of XP’s practices, since they reinforce each other. But nowadays there also exist many approaches that adopt one or a few of XP’s practices.

 

9.1.3 Scrum

Jeff Sutherland created the scrum process in 1993. Scrum is the leading agile development methodology. Scrum - framework within which people can address complex adaptive problems, while productively and creatively delivering products of the highest possible value.

Scrum is a process framework that has been used to manage complex product development.It is not a process or a technique for building products; rather, it is a framework within which you can employ various processes and techniques. Scrum makes clear the relative efficacy of your product management and development practices so that you can improve.

The Scrum framework consists of Scrum Teams and their associated roles, events, artifacts, and rules. Each component within the framework serves a specific purpose and is essential to Scrum’s success and usage.

The rules of Scrum bind together the events, roles, and artifacts, governing the relationships and interaction between them. The rules of Scrum are described throughout the body of this document.

Scrum is founded on empirical process control theory, or empiricism. Empiricism asserts that knowledge comes from experience and making decisions based on what is known. Scrum employs an iterative, incremental approach to optimize predictability and control risk. Three pillars uphold every implementation of empirical process control:

• Transparency - Significant aspects of the process must be visible to those responsible for the outcome. Transparency requires those aspects be defined by a common standard so observers share a common understanding of what is being seen.
• Inspection - Scrum users must frequently inspect Scrum artifacts and progress toward a Sprint Goal to detect undesirable variances. Their inspection should not be so frequent that inspection gets in the way of the work. Inspections are most beneficial when diligently performed by skilled inspectors at the point of work.
• Adaptation - If an inspector determines that one or more aspects of a process deviate outside acceptable limits, and that the resulting product will be unacceptable, the process or the material being processed must be adjusted. An adjustment must be made as soon as possible to minimize further deviation.

Scrum prescribes four formal events for inspection and adaptation:

• Sprint Planning
• Daily Scrum
• Sprint Review
• Sprint Retrospective

The Scrum Team

The Scrum Team consists of

• Product Owner
• Development Team
• Scrum Master.

Scrum Teams are self-organizing and cross-functional. Self-organizing teams choose how best to accomplish their work, rather than being directed by others outside the team. Cross-functional teams have all competencies needed to accomplish the work without depending on others not part of the team. The team model in Scrum is designed to optimize flexibility, creativity, and productivity.

Scrum Teams deliver products iteratively and incrementally, maximizing opportunities for feedback. Incremental deliveries of “Done” product ensure a potentially useful version of working product is always available.

The Product Owner

The Product Owner is responsible for maximizing the value of the product and the work of the Development Team. How this is done may vary widely across organizations, Scrum Teams, and individuals.

The Product Owner is the sole person responsible for managing the Product Backlog. Product Backlog management includes:

• Clearly expressing Product Backlog items;
• Ordering the items in the Product Backlog to best achieve goals and missions;
• Optimizing the value of the work the Development Team performs;
• Ensuring that the Product Backlog is visible, transparent, and clear to all, and shows what the Scrum Team will work on next; and,
• Ensuring the Development Team understands items in the Product Backlog to the level needed.

The Product Owner may do the above work, or have the Development Team do it. The Product Owner is one person, not a committee. The Product Owner may represent the desires of a committee in the Product Backlog, but those wanting to change a Product Backlog item’s priority must address the Product Owner.

For the Product Owner to succeed, the entire organization must respect his or her decisions. The Product Owner’s decisions are visible in the content and ordering of the Product Backlog. No one is allowed to tell the Development Team to work from a different set of requirements, and the Development Team isn’t allowed to act on what anyone else says.

The Development Team

The Development Team consists of professionals who do the work of delivering a potentially releasable Increment of “Done” product at the end of each Sprint. Only members of the Development Team create the Increment.

Development Teams are structured and empowered by the organization to organize and manage their own work. The resulting synergy optimizes the Development Team’s overall efficiency and effectiveness.

Development Teams have the following characteristics:

• They are self-organizing. No one (not even the Scrum Master) tells the Development Team how to turn Product Backlog into Increments of potentially releasable functionality;
• Development Teams are cross-functional, with all of the skills as a team necessary to create a product Increment;
• Scrum recognizes no titles for Development Team members other than Developer, regardless of the work being performed by the person; there are no exceptions to this rule;
• Scrum recognizes no sub-teams in the Development Team, regardless of particular domains that need to be addressed like testing or business analysis; there are no exceptions to this rule;
• Individual Development Team members may have specialized skills and areas of focus, but accountability belongs to the Development Team as a whole.

Optimal Development Team size is small enough to remain nimble and large enough to complete significant work within a Sprint. Fewer than three Development Team members decrease interaction and results in smaller productivity gains. Smaller Development Teams may encounter skill constraints during the Sprint, causing the Development Team to be unable to deliver a potentially releasable Increment. Having more than nine members requires too much coordination. Large Development Teams generate too much complexity for an empirical process to manage. The Product Owner and Scrum Master roles are not included in this count unless they are also executing the work of the Sprint Backlog.

The Scrum Master

The Scrum Master is responsible for ensuring Scrum is understood and enacted. Scrum Masters do this by ensuring that the Scrum Team adheres to Scrum theory, practices, and rules.

The Scrum Master is a servant-leader for the Scrum Team. The Scrum Master helps those outside the Scrum Team understand which of their interactions with the Scrum Team are helpful and which aren’t. The Scrum Master helps everyone change these interactions to maximize the value created by the Scrum Team.

The Scrum Master serves the Product Owner in several ways, including:

• Finding techniques for effective Product Backlog management;
• Helping the Scrum Team understand the need for clear and concise Product Backlog items;
• Understanding product planning in an empirical environment;
• Ensuring the Product Owner knows how to arrange the Product Backlog to maximize value;
• Understanding and practicing agility;
• Facilitating Scrum events as requested or needed.

The Scrum Master serves the Development Team in several ways, including:

• Coaching the Development Team in self-organization and cross-functionality;
• Helping the Development Team to create high-value products;
• Removing impediments to the Development Team’s progress;
• Facilitating Scrum events as requested or needed;
• Coaching the Development Team in organizational environments in which Scrum is not yet fully adopted and understood.

The Scrum Master serves the organization in several ways, including:

• Leading and coaching the organization in its Scrum adoption;
• Planning Scrum implementations within the organization;
• Helping employees and stakeholders understand and enact Scrum and empirical product development;
• Causing change that increases the productivity of the Scrum Team;
• Working with other Scrum Masters to increase the effectiveness of the application of Scrum in the organization.

Scrum Events

Prescribed events are used in Scrum to create regularity and to minimize the need for meetings not defined in Scrum. Every event has a maximum duration. Once a Sprint begins, its duration is fixed and cannot be shortened or lengthened. The remaining events may end whenever the purpose of the event is achieved, ensuring an appropriate amount of time is spent without allowing waste in the process.

Other than the Sprint itself, which is a container for all other events, each event in Scrum is a formal opportunity to inspect and adapt something. These events are specifically designed to enable critical transparency and inspection. Failure to include any of these events results in reduced transparency and is a lost opportunity to inspect and adapt.

The Sprint

The heart of Scrum is a Sprint, a time-box of one month or less during which a “Done”, useable, and potentially releasable product Increment is created. Sprints best have consistent durations throughout a development effort. A new Sprint starts immediately after the conclusion of the previous Sprint.

Sprints contain and consist of the Sprint Planning, Daily Scrums, the development work, the Sprint Review, and the Sprint Retrospective.

During the Sprint:

• No changes are made that would endanger the Sprint Goal;
• Quality goals do not decrease;
• Scope may be clarified and re-negotiated between the Product Owner and Development Team as more is learned.

Each Sprint may be considered a project with no more than a one-month horizon. Like projects, Sprints are used to accomplish something. Each Sprint has a definition of what is to be built, a design and flexible plan that will guide building it, the work, and the resultant product.

Sprints are limited to one calendar month. When a Sprint’s horizon is too long the definition of what is being built may change, complexity may rise, and risk may increase. Sprints enable predictability by ensuring inspection and adaptation of progress toward a Sprint Goal at least every calendar month. Sprints also limit risk to one calendar month of cost.

A Sprint can be cancelled before the Sprint time-box is over. Only the Product Owner has the authority to cancel the Sprint, although he or she may do so under influence from the stakeholders, the Development Team, or the Scrum Master.

A Sprint would be cancelled if the Sprint Goal becomes obsolete. This might occur if the company changes direction or if market or technology conditions change. In general, a Sprint should be cancelled if it no longer makes sense given the circumstances. But, due to the short duration of Sprints, cancellation rarely makes sense.

When a Sprint is cancelled, any completed and “Done” Product Backlog items are reviewed. If part of the work is potentially releasable, the Product Owner typically accepts it. All incomplete Product Backlog Items are re-estimated and put back on the Product Backlog. The work done on them depreciates quickly and must be frequently re-estimated.

Sprint cancellations consume resources, since everyone has to regroup in another Sprint Planning to start another Sprint. Sprint cancellations are often traumatic to the Scrum Team, and are very uncommon.

Sprint Planning

The work to be performed in the Sprint is planned at the Sprint Planning. This plan is created by the collaborative work of the entire Scrum Team.

Sprint Planning is time-boxed to a maximum of eight hours for a one-month Sprint. For shorter Sprints, the event is usually shorter. The Scrum Master ensures that the event takes place and that attendants understand its purpose. The Scrum Master teaches the Scrum Team to keep it within the time-box.

Sprint Planning answers the two topics:

• Topic One: What can be done this Sprint? 
  The Development Team works to forecast the functionality that will be developed during the Sprint. The Product Owner discusses the objective that the Sprint should achieve and the Product Backlog items that, if completed in the Sprint, would achieve the Sprint Goal. The entire Scrum Team collaborates on understanding the work of the Sprint.
  The input to this meeting is the Product Backlog, the latest product Increment, projected capacity of the Development Team during the Sprint, and past performance of the Development Team. The number of items selected from the Product Backlog for the Sprint is solely up to the Development Team. Only the Development Team can assess what it can accomplish over the upcoming Sprint. 
  After the Development Team forecasts the Product Backlog items it will deliver in the Sprint, the Scrum Team crafts a Sprint Goal. The Sprint Goal is an objective that will be met within the Sprint through the implementation of the Product Backlog, and it provides guidance to the Development Team on why it is building the Increment.
• Topic Two: How will the chosen work get done?
  Having set the Sprint Goal and selected the Product Backlog items for the Sprint, the Development Team decides how it will build this functionality into a “Done” product Increment during the Sprint. The Product Backlog items selected for this Sprint plus the plan for delivering them is called the Sprint Backlog. 
  The Development Team usually starts by designing the system and the work needed to convert the Product Backlog into a working product Increment. Work may be of varying size, or estimated effort. However, enough work is planned during Sprint Planning for the Development Team to forecast what it believes it can do in the upcoming Sprint. Work planned for the first days of the Sprint by the Development Team is decomposed by the end of this meeting, often to units of one day or less. The Development Team self-organizes to undertake the work in the Sprint Backlog, both during Sprint Planning and as needed throughout the Sprint. 
  The Product Owner can help to clarify the selected Product Backlog items and make trade-offs. If the Development Team determines it has too much or too little work, it may renegotiate the selected Product Backlog items with the Product Owner. The Development Team may also invite other people to attend in order to provide technical or domain advice.

By the end of the Sprint Planning, the Development Team should be able to explain to the Product Owner and Scrum Master how it intends to work as a self-organizing team to accomplish the Sprint Goal and create the anticipated Increment.

Sprint Goal

The Sprint Goal is an objective set for the Sprint that can be met through the implementation of Product Backlog. It provides guidance to the Development Team on why it is building the Increment. It is created during the Sprint Planning meeting. The Sprint Goal gives the Development Team some flexibility regarding the functionality implemented within the Sprint. The selected Product Backlog items deliver one coherent function, which can be the Sprint Goal. The Sprint Goal can be any other coherence that causes the Development Team to work together rather than on separate initiatives.

As the Development Team works, it keeps the Sprint Goal in mind. In order to satisfy the Sprint Goal, it implements the functionality and technology. If the work turns out to be different than the Development Team expected, they collaborate with the Product Owner to negotiate the scope of Sprint Backlog within the Sprint.

Daily Scrum

The Daily Scrum is a 15-minute time-boxed event for the Development Team to synchronize activities and create a plan for the next 24 hours. This is done by inspecting the work since the last Daily Scrum and forecasting the work that could be done before the next one. The Daily Scrum is held at the same time and place each day to reduce complexity. During the meeting, the Development Team members explain:

• What did I do yesterday that helped the Development Team meet the Sprint Goal?
• What will I do today to help the Development Team meet the Sprint Goal?
• Do I see any impediment that prevents me or the Development Team from meeting the Sprint Goal?

The Development Team uses the Daily Scrum to inspect progress toward the Sprint Goal and to inspect how progress is trending toward completing the work in the Sprint Backlog. The Daily Scrum optimizes the probability that the Development Team will meet the Sprint Goal. Every day, the Development Team should understand how it intends to work together as a self-organizing team to accomplish the Sprint Goal and create the anticipated Increment by the end of the Sprint. The Development Team or team members often meet immediately after the Daily Scrum for detailed discussions, or to adapt, or replan, the rest of the Sprint’s work.

The Scrum Master ensures that the Development Team has the meeting, but the Development Team is responsible for conducting the Daily Scrum. The Scrum Master teaches the Development Team to keep the Daily Scrum within the 15-minute time-box.

The Scrum Master enforces the rule that only Development Team members participate in the Daily Scrum.

Daily Scrums improve communications, eliminate other meetings, identify impediments to development for removal, highlight and promote quick decision-making, and improve the Development Team’s level of knowledge. This is a key inspect and adapt meeting.

Sprint Review

A Sprint Review is held at the end of the Sprint to inspect the Increment and adapt the Product Backlog if needed. During the Sprint Review, the Scrum Team and stakeholders collaborate about what was done in the Sprint. Based on that and any changes to the Product Backlog during the Sprint, attendees collaborate on the next things that could be done to optimize value. This is an informal meeting, not a status meeting, and the presentation of the Increment is intended to elicit feedback and foster collaboration.

This is a four-hour time-boxed meeting for one-month Sprints. For shorter Sprints, the event is usually shorter. The Scrum Master ensures that the event takes place and that attendants understand its purpose. The Scrum Master teaches all to keep it within the time-box.

The Sprint Review includes the following elements:

• Attendees include the Scrum Team and key stakeholders invited by the Product Owner;
• The Product Owner explains what Product Backlog items have been “Done” and what has not been “Done”;
• The Development Team discusses what went well during the Sprint, what problems it ran into, and how those problems were solved;
• The Development Team demonstrates the work that it has “Done” and answers questions about the Increment;
• The Product Owner discusses the Product Backlog as it stands. He or she projects likely completion dates based on progress to date (if needed);
• The entire group collaborates on what to do next, so that the Sprint Review provides valuable input to subsequent Sprint Planning;
• Review of how the marketplace or potential use of the product might have changed what is the most valuable thing to do next;
• Review of the timeline, budget, potential capabilities, and marketplace for the next anticipated release of the product.

The result of the Sprint Review is a revised Product Backlog that defines the probable Product Backlog items for the next Sprint. The Product Backlog may also be adjusted overall to meet new opportunities.

Sprint Retrospective

The Sprint Retrospective is an opportunity for the Scrum Team to inspect itself and create a plan for improvements to be enacted during the next Sprint.

The Sprint Retrospective occurs after the Sprint Review and prior to the next Sprint Planning. This is a three-hour time-boxed meeting for one-month Sprints. For shorter Sprints, the event is usually shorter. The Scrum Master ensures that the event takes place and that attendants understand its purpose. The Scrum Master teaches all to keep it within the time-box. The Scrum Master participates as a peer team member in the meeting from the accountability over the Scrum process.

The purpose of the Sprint Retrospective is to:

• Inspect how the last Sprint went with regards to people, relationships, process, and tools;
• Identify and order the major items that went well and potential improvements;
• Create a plan for implementing improvements to the way the Scrum Team does its work.

The Scrum Master encourages the Scrum Team to improve, within the Scrum process framework, its development process and practices to make it more effective and enjoyable for the next Sprint. During each Sprint Retrospective, the Scrum Team plans ways to increase product quality by adapting the definition of “Done” as appropriate.

By the end of the Sprint Retrospective, the Scrum Team should have identified improvements that it will implement in the next Sprint. Implementing these improvements in the next Sprint is the adaptation to the inspection of the Scrum Team itself. Although improvements may be implemented at any time, the Sprint Retrospective provides a formal opportunity to focus on inspection and adaptation.

Product Backlog

The Product Backlog is an ordered list of everything that might be needed in the product and is the single source of requirements for any changes to be made to the product. The Product Owner is responsible for the Product Backlog, including its content, availability, and ordering.

A Product Backlog is never complete. The earliest development of it only lays out the initially known and best-understood requirements. The Product Backlog evolves as the product and the environment in which it will be used evolves. The Product Backlog is dynamic; it constantly changes to identify what the product needs to be appropriate, competitive, and useful. As long as a product exists, its Product Backlog also exists.

The Product Backlog lists all features, functions, requirements, enhancements, and fixes that constitute the changes to be made to the product in future releases. Product Backlog items have the attributes of a description, order, estimate and value.

As a product is used and gains value, and the marketplace provides feedback, the Product Backlog becomes a larger and more exhaustive list. Requirements never stop changing, so a Product Backlog is a living artifact. Changes in business requirements, market conditions, or technology may cause changes in the Product Backlog.

Multiple Scrum Teams often work together on the same product. One Product Backlog is used to describe the upcoming work on the product. A Product Backlog attribute that groups items may then be employed.

Product Backlog refinement is the act of adding detail, estimates, and order to items in the Product Backlog. This is an ongoing process in which the Product Owner and the Development Team collaborate on the details of Product Backlog items. During Product Backlog refinement, items are reviewed and revised. The Scrum Team decides how and when refinement is done. Refinement usually consumes no more than 10% of the capacity of the Development Team. However, Product Backlog items can be updated at any time by the Product Owner or at the Product Owner’s discretion.

Higher ordered Product Backlog items are usually clearer and more detailed than lower ordered ones. More precise estimates are made based on the greater clarity and increased detail; the lower the order, the less detail. Product Backlog items that will occupy the Development Team for the upcoming Sprint are refined so that any one item can reasonably be “Done” within the Sprint time-box. Product Backlog items that can be “Done” by the Development Team within one Sprint are deemed “Ready” for selection in a Sprint Planning. Product Backlog items usually acquire this degree of transparency through the above described refining activities.

The Development Team is responsible for all estimates. The Product Owner may influence the Development Team by helping it understand and select trade-offs, but the people who will perform the work make the final estimate.

Sprint Backlog

The Sprint Backlog is the set of Product Backlog items selected for the Sprint, plus a plan for delivering the product Increment and realizing the Sprint Goal. The Sprint Backlog is a forecast by the Development Team about what functionality will be in the next Increment and the work needed to deliver that functionality into a “Done” Increment.

The Sprint Backlog makes visible all of the work that the Development Team identifies as necessary to meet the Sprint Goal.

The Sprint Backlog is a plan with enough detail that changes in progress can be understood in the Daily Scrum. The Development Team modifies the Sprint Backlog throughout the Sprint, and the Sprint Backlog emerges during the Sprint. This emergence occurs as the Development Team works through the plan and learns more about the work needed to achieve the Sprint Goal.

As new work is required, the Development Team adds it to the Sprint Backlog. As work is performed or completed, the estimated remaining work is updated. When elements of the plan are deemed unnecessary, they are removed. Only the Development Team can change its Sprint Backlog during a Sprint. The Sprint Backlog is a highly visible, real-time picture of the work that the Development Team plans to accomplish during the Sprint, and it belongs solely to the Development Team.

When a Product Backlog item or an Increment is described as “Done”, everyone must understand what “Done” means. Although this varies significantly per Scrum Team, members must have a shared understanding of what it means for work to be complete, to ensure transparency. This is the definition of “Done” for the Scrum Team and is used to assess when work is complete on the product Increment.

The same definition guides the Development Team in knowing how many Product Backlog items it can select during a Sprint Planning. The purpose of each Sprint is to deliver Increments of potentially releasable functionality that adhere to the Scrum Team’s current definition of “Done.” Development Teams deliver an Increment of product functionality every Sprint. This Increment is useable, so a Product Owner may choose to immediately release it. If the definition of "done" for an increment is part of the conventions, standards or guidelines of the development organization, all Scrum Teams must follow it as a minimum. If "done" for an increment is not a convention of the development organization, the Development Team of the Scrum Team must define a definition of “done” appropriate for the product. If there are multiple Scrum Teams working on the system or product release, the development teams on all of the Scrum Teams must mutually define the definition of “Done.”

Each Increment is additive to all prior Increments and thoroughly tested, ensuring that all Increments work together.

As Scrum Teams mature, it is expected that their definitions of “Done” will expand to include more stringent criteria for higher quality. Any one product or system should have a definition of “Done” that is a standard for any work done on it.

9.2 Agile team

An agile team has next characteristics: collocated, rapid communication channels, a people-oriented attitude. Often, people work in pairs, with a pilot and co-pilot, but without a hierarchy.

Because agile processes have little discipline enforced on them from the outside, they need discipline to come from within the team. Agile teams need self-discipline. If a pair of programmers develops some code and subsequent tests fail, they must take a step back and redo their work. After they have incorporated a piece of work, they must consider the system as a whole and refactor if needed.

For this to succeed, an agile team needs skilled people than a team that works according to more formal approach with strong plan which often called a planning-driven approach. In a planning-driven approach the plan works like a life-jacket for the project. In an agile team, no such life-jacket is available, and people must have special skills to make successful project. In terms of Cockburn’s levels of understanding (see Figure 9.4), an agile team requires level 2 or 3 people, and is deemed risky with level 1 people. In planning-driven environments, level 2 or 3 people are only required during the definition stages of development. Thereafter, some level 1 people can be accommodated.