“Anything that can go wrong, will—at the worst possible moment”
WHAT IS SCRUM?
Scrum: A framework within which people can address complex adaptive problems, while productively and creatively delivering products of the highest possible value.
- Simple to understand
- Difficult to master
Scrum is not:
- A process
- A technique
- A definitive method
Scrum makes clear the relative efficacy of your product management and work techniques so that you can continuously improve the product, the team, and the working environment.
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 roles, events, and artifacts, governing the relationships and interaction between them..
USES OF SCRUM
Scrum was initially developed for managing and developing products. Starting in the early 1990s, Scrum has been used extensively, worldwide, to:
- Research and identify viable markets, technologies, and product capabilities
- Develop products and enhancements
- Release products and enhancements, as frequently as many times per day
- Develop and sustain Cloud (online, secure, on-demand) and other operational
environments for product use
- Sustain and renew products.
Scrum has been used to develop software, hardware, embedded software, networks of interacting function, autonomous vehicles, schools, government, marketing, managing the operation of organizations and almost everything we use in our daily lives, as individuals and societies.
As technology, market, and environmental complexities and their interactions have rapidly increased, Scrum’s utility in dealing with complexity is proven daily. Scrum proved especially effective in iterative and incremental knowledge transfer. Scrum is now widely used for products, services, and the management of the parent organization.
The essence of Scrum is a small team of people. The individual team is highly flexible and adaptive. These strengths continue operating in single, several, many, and networks of teams that develop, release, operate and sustain the work and work products of thousands of people.
They collaborate and interoperate through sophisticated development architectures and target release environments. When the words “develop” and “development” are used in the Scrum Guide, they refer to complex work, such as those types identified above.
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, inspection, and adaptation.
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
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.
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, as described in the Scrum Events section of this document:
- Sprint Planning
- Daily Scrum
- Sprint Review
- Sprint Retrospective
When the values of commitment, courage, focus, openness and respect are embodied and lived by the Scrum Team, the Scrum pillars of transparency, inspection, and adaptation come to life and build trust for everyone. The Scrum Team members learn and explore those values as they work with the Scrum roles, events, and artifacts.
Successful use of Scrum depends on people becoming more proficient in living these five values. People personally commit to achieving the goals of the Scrum Team. The Scrum Team members have courage to do the right thing and work on tough problems. Everyone focuses on the work of the Sprint and the goals of the Scrum Team. The Scrum Team and its stakeholders agree to be open about all the work and the challenges with performing the work. Scrum Team members respect each other to be capable, independent people.
THE SCRUM TEAM
The Scrum Team consists of a Product Owner, the Development Team, and a 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. The Scrum Team has proven itself to be increasingly effective for all the earlier stated uses, and any complex work.
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 resulting from 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
- 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. However, the Product Owner remains accountable.
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 can force the Development Team to work from a different set of requirements.
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. A “Done” increment is required at the Sprint Review. 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 the skills as a team necessary to create a product Increment
- Scrum recognizes no titles for Development Team members, regardless of the work being performed by the person
- Scrum recognizes no sub-teams in the Development Team, regardless of domains that need to be addressed like testing, architecture, operations, or business analysis
- 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 be useful. 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 promoting and supporting Scrum as defined in the Scrum Guide. Scrum Masters do this by helping everyone understand Scrum theory, practices, rules, and values.
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.
Scrum Master service to the Product Owner
- Ensuring that goals, scope, and product domain are understood by everyone on the Scrum Team as well as possible
- 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.
Scrum Master Service to the Development Team
- 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.
Scrum Master Service to the Organization
- 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
- 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
Prescribed events are used in Scrum to create regularity and to minimize the need for meetings not defined in Scrum. All events are time-boxed events, such that 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 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 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 goal of what is to be built, a design and flexible plan that will guide building it, the work, and the resultant product increment.
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.
Cancelling a Sprint
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 regroups in another Sprint Planning to start another Sprint. Sprint cancellations are often traumatic to the Scrum Team, and are very uncommon.
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 following:
- What can be delivered in the Increment resulting from the upcoming 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.
During Sprint Planning the Scrum Team also 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.
- How will the work needed to deliver the Increment be achieved?
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 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.
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 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.
The Daily Scrum is a 15-minute time-boxed event for the Development Team. The Daily Scrum is held every day of the Sprint. At it, the Development Team plans work for the next 24 hours. This optimizes team collaboration and performance by inspecting the work since the last Daily Scrum and forecasting upcoming Sprint work. The Daily Scrum is held at the same time and place each day to reduce complexity.
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 selforganizing team to accomplish the Sprint Goal and create the anticipated Increment by the end of the Sprint.
The structure of the meeting is set by the Development Team and can be conducted in different ways if it focuses on progress toward the Sprint Goal. Some Development Teams will use questions, some will be more discussion based. Here is an example of what might be used:
- 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 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 Daily Scrum is an internal meeting for the Development Team. If others are present, the Scrum Master ensures that they do not disrupt the meeting.
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.
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 at most a four-hour meeting for one-month Sprints. For shorter Sprints, the event is usually shorter. The Scrum Master ensures that the event takes place and that attendees understand its purpose. The Scrum Master teaches everyone involved to keep it within the timebox.
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
target and delivery 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 releases of functionality or capability 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.
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 at most a three-hour 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 ensures that the meeting is positive and productive. 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 improving work processes or adapting the definition of “Done”, if appropriate and not in conflict with product or organizational standards.
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.
Scrum’s artifacts represent work or value to provide transparency and opportunities for inspection and adaptation. Artifacts defined by Scrum are specifically designed to maximize transparency of key information so that everybody has the same understanding of the artifact.
The Product Backlog is an ordered list of everything that is known to be needed in the product. It 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 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. If 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. Product Backlog items often include test descriptions that will prove its completeness when “Done.”
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
Monitoring progress toward goals
At any point in time, the total work remaining to reach a goal can be summed. The Product Owner tracks this total work remaining at least every Sprint Review. The Product Owner compares this amount with work remaining at previous Sprint Reviews to assess progress toward completing projected work by the desired time for the goal. This information is made transparent to all stakeholders.
Various projective practices upon trending have been used to forecast progress, like burndowns, burn-ups, or cumulative flows. These have proven useful. However, these do not replace the importance of empiricism. In complex environments, what will happen is unknown. Only what has already happened may be used for forward-looking decision-making.
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 the work that the Development Team identifies as necessary to meet the Sprint Goal. To ensure continuous improvement, it includes at least one high priority process improvement identified in the previous Retrospective meeting.
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.
Monitor sprint progress
At any point in time in a Sprint, the total work remaining in the Sprint Backlog can be summed. The Development Team tracks this total work remaining at least for every Daily Scrum to project the likelihood of achieving the Sprint Goal. By tracking the remaining work throughout the Sprint, the Development Team can manage its progress.
The Increment is the sum of all the Product Backlog items completed during a Sprint and the value of the increments of all previous Sprints. At the end of a Sprint, the new Increment must be “Done,” which means it must be in useable condition and meet the Scrum Team’s definition of “Done.” An increment is a body of inspectable, done work that supports empiricism at the end of the Sprint. The increment is a step toward a vision or goal. The increment must be in useable condition regardless of whether the Product Owner decides to release it.
Scrum relies on transparency. Decisions to optimize value and control risk are made based on the perceived state of the artifacts. To the extent that transparency is complete, these decisions have a sound basis. To the extent that the artifacts are incompletely transparent, these decisions can be flawed, value may diminish and risk may increase.
The Scrum Master must work with the Product Owner, Development Team, and other involved parties to understand if the artifacts are completely transparent. There are practices for coping with incomplete transparency; the Scrum Master must help everyone apply the most appropriate practices in the absence of complete transparency. A Scrum Master can detect incomplete transparency by inspecting the artifacts, sensing patterns, listening closely to what is being said, and detecting differences between expected and real results.
The Scrum Master’s job is to work with the Scrum Team and the organization to increase the transparency of the artifacts. This work usually involves learning, convincing, and change.
Transparency doesn’t occur overnight, but is a path.
DEFINITION OF DONE
When a Product Backlog item or an Increment is described as “Done”, everyone must understand what “Done” means. Although this may vary 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 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. New definitions, as used, may uncover work to be done in previously “Done” increments. Any one product or system should have a definition of “Done” that is a standard for any work done on it.
Taken from “The Scrum Guide” (November 2017 edition of the Scrum alliance)
©2017 Ken Schwaber and Jeff Sutherland
“Individuals and interactions over processes and tools.”
Paying attention to individuals, the people on the team as opposed to roles in the process chart. Not all practices in software world are appropriate for every project, team and situation; while it is of utmost importance to understand the people in the team, how they work together and how each individual’s work impacts everyone else.
Although a process description is needed to get a group of people started, people are going to develop the program, and can go wrong when blindly following a process, or making use of tools that drive them to get faster an incorrect result.
But all the work is not carried out individually, being of relevance attending to the interactions between the individuals. New solutions and flaws in old solutions come to life in discussions between
people. The quality of the interactions matters, being preferable to use an undocumented process with good interactions than a documented process with hostile interactions.
“Working software over comprehensive documentation.”
There are binders full of complete and comprehensive software documentation sitting unopened on shelves all over the world. There is so much that can be documented in a software project, and it’s often difficult during the heat of the project to predict what’s going to be useful in the future, and what will gather dust. Because of that, a lot of teams—and especially their managers—will decide on a comprehensive approach, where every little thing must be documented, no matter whether or not
there’s a potential reader for the document.
On the other hand, a working system is the only way to measure the real work done built the team. Running code is ruthlessly honest, while documents showing the requirements, analysis, design, screen flows, sequence charts… are handy as hints to aid the team, together with their own experience, to guess what the future will look like
What does the word “working” really mean? To an agile practitioner, working software is software that adds value to the organization. It could be software that a company sells to make money, or it could be software that people who work at the company use to do their jobs more efficiently.
Valuing working software over comprehensive documentation does not mean that no documentation is needed; there are many kinds of documents that are very useful for the team. But it’s important to keep in mind that the people writing the documentation are often the same people who are writing the software.
Documents serve as markers in the game, used to build an image of the unreliable future. On the other hand, the composite act of gathering requirements, designing, coding, and debugging the software, reveals information about the development team, the development process, and the nature of the problem to be solved. Those things together with the running final result provide the only reliable measure of the speed of the team, the shortcomings of the group, and a glimpse into what the team really should be building.
“Customer collaboration over contract negotiation.”
There should not be a “us” or “them” when referring to people involved in the project. Independently of the task of building or providing requirements the team is performing, there should only be “us”. Both sides are needed to produce good software.
Although contracts are useful at times, collaboration strengthens development both when there is a contract in place and when there is none. Good collaboration can save a contract situation when it is in jeopardy. Good collaboration can sometimes make a contract unnecessary. Either way, collaboration is the winning element.
“Responding to change over following a plan.”
There’s an old project management saying: “plan the work, work the plan.” Unfortunately, if you work the wrong plan, you’ll build the wrong product. That’s why teams need to constantly look for changes, and to make sure that they respond appropriately when there’s a change in what the users need, or in how the software needs to be built. If the circumstances change, the project needs a new plan.
Building a plan is useful, and each of the agile methodologies contains specific planning activities. They also contain mechanisms for dealing with changing priorities, guaranteeing that the team has the time and peace of mind to develop working software.
How these values shape Agile
Out of these four values, the following points can be used to summarize the Agile basic tenets.
- Redefined roles for developers, managers and customers.
- No “Big Upfront” steps.
- Iterative development.
- Limited, negotiated functionality.
- Focus on quality, understood as achieved through testing.
The first tenet affects a fundamental feature of project development: the role of developers and managers. Agile methods redefine and limit the manager’s job by transferring many of the duties to the team as a whole, including one of the most important responsibilities: selecting tasks to be performed and assigning them to developers. It is possible to give a sociological interpretation of the agile movement as a “revolt of the cubicles”: the rejection of rigid, top-down, Dilbert’s-boss-like techniques for managing software projects. Programmers in the trenches — the cubicles — often resent these attempts as ignorant of the specific nature of software development. The Dilbert types know that documents and diagrams do not make a system: code does. Agile methods are, in part, the rehabilitation of code.
The redefinition of roles also affects customers, who in the agile world are not passive recipients of the software but active participants. Most methods advocate including a customer representative in the development team itself.
The second tenet is the rejection of “Big Upfront Anything”, a term used derogatorily for standard software engineering techniques involving extensive planning at the beginning of a project; the principal examples are requirements, to define the goals of the system, and design, to define its architecture. In the agile view:
- Requirements cannot be captured at the beginning of a project, because users do not know what they want. Even if one managed to write a requirements document, it would be useless because requirements will change through the project.
- Building a design upfront is a waste of time because we do not know what will work and what will not.
Instead of a requirements document, agile methods recommend constant interaction with the customer — hence the benefit of a customer representative in the team — to get both insights into the problem and feedback on what has been produced so far. Instead of design, the recommendation is to build the system iteratively, devising at each step the “simplest solution that can possibly work” (an Extreme Programming slogan) for the task at hand; then, if the solution turns out to be imperfect, improving its design through a process known as refactoring. Agile development, as a consequence, is iterative, time-boxed development.
The agile alternative to a requirements document is, at the beginning of each iteration, a prioritized list of functions from which the team will select for implementation the function that has the highest Return on Investment (ROI). In the absence of big upfront tasks, this choice will be made in successive steps, (e.g.: the “sprints” in Scrum) each taking a fixed time — a few weeks — hence “time-boxed”. The development thus proceeds by iterative addition of functionality.
The “negotiation” occurs at the step of choosing the functionality for each iteration. Just as it is impossible, in the agile view, to determine full requirements in advance, it is unrealistic to commit to both functionality and delivery time. With time-boxed development, any tradeoffs (“do you want it all or do you want it next month?”) will tend to be resolved in favor of the second criterion: if not all the functions planned for an iteration can be delivered by the deadline, it is the functionality that goes; the deadline stays. The missed functionality will either be reassigned to a subsequent phase or — if further analysis deems its ROI insufficient — dropped. This process of planning and adjusting requires constant negotiation with the customer.
The final tenet is the focus on quality, which in the agile view essentially means continuous testing (rather than other approaches to quality, in particular those based on design techniques, formal programming methodology, or whatever smacks of “Big Upfront”).
The agile approach has little patience with what it sees as the languid attention to quality in traditional development; it especially dislikes the practice of continuing to develop functionality even when the code already developed does not pass all the tests.
One of its contributions is to emphasize the role of a project’s regression test suite: the set of tests that must pass, including all tests that at some point did not pass and hence revealed faults that were then fixed. Regression testing has been known and applied for a long time, but agile methods have given this task a central place in the development process.
Good cooking fakes time. If you are made to wait, it is to serve you better, and to please you
MENU OF RESTAURANT ANTOINE. NEW ORLEANS
More projects go wrong because of lack of time than other factors.
- Estimation techniques are poorly developed (optimistically assuming that “all will go well”)
- Estimation techniques fallaciously confuse effort with progress (assuming men and time are interchangeable)
- We are uncertain of our estimates
- Schedule progress is poorly monitored
- When schedule delay is identified, the natural (and traditional) response is to add manpower (which makes matters worse, much worse)
All programmers are optimists. Why?, maybe…
- this modern sorcery (programming) especially attracts those who believe in happy endings and fairy godmothers.
- the hundreds of nitty frustrations drive away all but those who habitually focus on the end goal.
- it is merely that computers are young, programmers are younger, and the young are always optimists.
- IDEA – a program comes into existence first as an ideal construct, built outside time and space, but complete in the mind of the author
- IMPLEMENTATION – built in time and space, by pen, ink, and paper, or by wire, silicon, and ferrite.
- INTERACTION – when the user is making use of it
Traditional activities reveal the incompleteness and inconsistencies of our ideas during implementation, which takes time and sweat both because of the physical media and because of the inadequacies of the underlying ideas.
On the other hand, the programmer builds from pure thought-stuff, in a very tractable medium. Because of it, we expect few difficulties in implementation; hence our pervasive optimism. But our ideas are faulty, so have bugs; hence our optimism is unjustified.
In a single task, the assumption that “all will go well” has a probabilistic effect on the schedule where it might not go well.
A large programming effort, however, consists of many tasks, some chained end-to-end. The probability that each will go well becomes vanishingly small.
It is erroneous to consider that people and months are interchangeable, which is reflected in the unit of effort used in estimating and scheduling: the man-month.
- Cost varies according to the number of men and the number of months.
- Progress does not.
The man-month as a unit for measuring the size of a job is a dangerous and deceptive myth.
TYPES OF DIFFERENT TASKS AND ITS MEN-TIME INTERCHANGEABILITY:
- Tasks that can be partitioned (with no need for communication among workers):
Men and months are interchangeable commodities as it presents workers with no communication among them.
EXAMPLE: reaping wheat or picking cotton
- Tasks that cannot be partitioned because of sequential constraints
The application of more effort has no effect on the schedule.
EXAMPLE: The bearing of a child takes nine months, no matter how many women are assigned.
- Tasks that can be partitioned (with needs for communication among the subtasks)
The effort of communication must be added to the amount of work to be done. Therefore the best that can be done is somewhat poorer than an even trade of men for months.
The added burden of communication is made up of two parts
- TRAINING: in the technology, the goals of the effort, the overall strategy, and the plan of work. This training cannot be partitioned, so this part of the added effort varies linearly with the number of workers.
- INTERCOMMUNICATION: If each part of the task must be separately coordinated with each other part/ the effort increases as n(n-I)/2. Three workers require three times as much pairwise intercommunication as two; four require six times as much as two.
If, moreover, there need to be conferences among three, four, etc., workers to resolve things jointly, matters get worse yet. The added effort of communicating may fully counteract the division of the original task.
Software development is inherently a systems effort—an exercise in complex interrelationships—communication effort is great, and it quickly dominates the decrease in individual task time brought about by partitioning. Adding more men then lengthens, not shortens, the schedule.
Sequential constraints especially affect component debugging and system test. The time required depends on the number and subtlety of the errors encountered. (Theoretically this number should be zero.)
>> We expect less bugs than it turns out to be
>> testing runs out of (mis)scheduled time
Rule of thumb for scheduling a software task:
- l/3 planning
- l/6 coding
- l/4 component test and early system test
- l/4 system test, all components in hand.
This differs from conventional scheduling in several important ways:
- The fraction devoted to planning is larger than normal. Even so, it is barely enough to produce a detailed and solid specification, and not enough to include research or exploration of totally new techniques.
- The half of the schedule devoted to debugging of completed code is much larger than normal.
- The part that is easy to estimate, i.e., coding, is given only one-sixth of the schedule.
Not assigning enough time for test is disastrous. Delay on testing phase comes at the end, so it is realized in the verge of delivery date. Bad news, late and without warning; for both customers and managers.
- Direct costs on development project.
- Indirect costs to the functionalities for which this project is being developed.
Urgency on the managerial side affects the schedule, but has nothing to do with the real time required for development. Once estimated time has been passed, customer has two choices—wait or “eat it raw”.
False scheduling to match client’s desired date is much more common in Software Development than elsewhere in engineering.
It is extremely complicated to make a real plausible estimation derived by no quantitative method, not enough data which is accepted by managers.
Clearly two solutions are needed. We need to develop and publicize productivity figures, bug-incidence figures, estimating rules, and so on. The whole prof ession can only profit from sharing such data.
Until estimating is on a sounder basis, individual managers will need to stiffen their backbones and defend their estimates with the assurance that their poor hunches are better than wishderived estimates.
Regenerative Schedule Disaster
Problem: a project behind schedule.
- Include extra people to meet time requirements. This will imply additional –and not available time- for training, additional testing,… creating a new delay.
- Reschedule, allowing time enough to ensure the work to be carefully and thoroughly done (so, no need for future rescheduling)
- Trim the task (which in practice trends to occurred anyway when adding additional people)
Oversimplifying outrageously: BROOK’S LAW:
“Adding manpower to a late software project makes it later”
This then is the demythologizing of the man-month:
- The number of months of a project depends upon its sequential constraints.
- The maximum number of men depends upon the number of independent subtasks.
From these two quantities one can derive schedules using fewer men and more months. (The only risk is product obsolescence.) One cannot, however, get workable schedules using more men and fewer months. More software projects have gone awry for lack of calendar time than for all other causes combined.
“work expands so as to fill the time available for its completion”
Stock–Sanford corollary to Parkinson’s law:
“if you wait until the last minute, it only takes a minute to do”
Horstman‘s corollary to Parkinson’s law:
“work contracts to fit in the time we give it”
“the demand upon a resource tends to expand to match the supply of the resource.”
“(the reverse is not true)”
Some define the law in regard to time as:
“the amount of time that one has to perform a task is the amount of time it will take to complete the task”