This article is an excerpt of Scrum Guide  by Ken Schwaber & Jeff Sutherland.
A framework within which people can address complex adaptive problems, while productively and creatively delivering products of the highest possible value. Scrum is:
- Simple to understand
- Extremely difficult to master
Scrum is a process framework that has been used to manage complex product development since the early 1990s. Scrum 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. Specific strategies for using the Scrum framework vary and are described elsewhere. 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:
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. For example:
- A common language referring to the process must be shared by all participants; and,
- A common definition of “Done” must be shared by those performing the work and those accepting the work product.
Scrum users must frequently inspect Scrum artifacts and progress toward a 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 opportunities for inspection and adaptation, as described in the Scrum Events section of this document.
Scrum is a framework structured to support complex product development. Scrum 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 Scrum Team
The Scrum Team consists of a 
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;
- Ensuring 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. 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 backlog item’s priority must convince 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 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 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;
- Individual Development Team members may have specialized skills and areas of focus, but accountability belongs to the Development Team as a whole; and,
- Development Teams do not contain sub-teams dedicated to particular domains like testing or business analysis.
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
- Clearly communicating vision, goals, and Product Backlog items to the Development Team
- Teaching the Scrum Team to create clear and concise Product Backlog items
- Understanding long-term product planning in an empirical environment
- 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
- Teaching and leading 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.
Prescribed events are used in Scrum to create regularity and to minimize the need for meetings not defined in Scrum. Scrum uses time-boxed events, such that every event has a maximum duration. This ensures an appropriate amount of time is spent planning without allowing waste in the planning 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”, use-able, 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 Meeting, Daily Scrums, the development work, the Sprint Review, and the Sprint Retrospective.
During the Sprint:
- No changes are made that would affect the Sprint Goal
- Development Team composition remains constant
- 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 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/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.
- When a Sprint is cancelled, any completed and “Done” Product Backlog Items are reviewed.
- Sprint cancellations consume resources, since everyone has to regroup in another Sprint Planning Meeting to start another Sprint.
- Sprint cancellations are often traumatic to the Scrum Team, and are very uncommon.
Sprint Planning Meeting
The work to be performed in the Sprint is planned at the Sprint Planning Meeting. This plan is created by the collaborative work of the entire Scrum Team.
The Sprint Planning Meeting is time-boxed to eight hours for a one-month Sprint. For shorter Sprints, the event is proportionately shorter. For example, two-week Sprints have four-hour Sprint Planning Meetings.
The Sprint Planning Meeting consists of two parts, each one being a time-box of one half of the Sprint Planning Meeting duration. The two parts of the Sprint Planning Meeting answer the following questions, respectively:
- What will be delivered in the Increment resulting from the upcoming Sprint?
- How will the work needed to deliver the Increment be achieved?
- What will be done this Sprint?
- The Development Team works to forecast the functionality that will be developed during the Sprint.
- The Product Owner presents ordered Product Backlog items to the Development Team.
- The entire Scrum Team collaborates on understanding the work of the Sprint.
- How will the chosen work get done?
- 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 decides how it will build this functionality into a “Done” product Increment during the Sprint.
The Sprint Goal gives the Development Team some flexibility regarding the functionality implemented within the Sprint.
As the Development Team works, it keeps this 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, then they collaborate with the Product Owner to negotiate the scope of Sprint Backlog within the Sprint. The Sprint Goal may be a milestone in the larger purpose of the product roadmap.
As the Development Team works, it keeps this 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, then 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 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, each Development Team member explains:
- What has been accomplished since the last meeting?
- What will be done before the next meeting?
- What obstacles are in the way?
The Development Team uses the Daily Scrum to assess progress toward the Sprint Goal and to assess 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. The Development Team often meets immediately after the Daily Scrum to re-plan the rest of the Sprint’s work. Every day, the Development Team should be able to explain to the Product Owner and Scrum Master how it intends to work together as a self-organizing team to accomplish the goal and create the anticipated Increment in the remainder of the Sprint.
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. The Daily Scrum is not a status meeting, and is for the people transforming the Product Backlog items into an Increment.
Daily Scrums improve communications, eliminate other meetings, identify and remove impediments to development, highlight and promote quick decision-making, and improve the Development Team’s level of project 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. This is an informal 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. Proportionately less time is allocated for shorter Sprints. For example, two week Sprints have two-hour Sprint Reviews. The Sprint Review includes the following elements:
- The Product Owner identifies what has 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
- The entire group collaborates on what to do next, so that the Sprint Review provides valuable input to subsequent Sprint Planning Meetings.
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 Meeting. This is a three-hour time-boxed meeting for one-month Sprints. Proportionately less time is allocated for shorter Sprints.
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.
Scrum’s artifacts represent work or value in various ways that are useful in providing transparency and opportunities for inspection and adaptation. Artifacts defined by Scrum are specifically designed to maximize transparency of key information needed to ensure Scrum Teams are successful in delivering a “Done” Increment.
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 Product Backlog lists all features, functions, requirements, enhancements, and fixes.
- The Product Backlog is often ordered by value, risk, priority, and necessity.
- Higher ordered Product Backlog items are clearer and more detailed than lower ordered ones.
- The Development Team is responsible for all estimates.
Monitoring Progress Toward a Goal
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 for 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.
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.
Monitoring Sprint Progress
At any point in time in a Sprint, the total work remaining in the Sprint Backlog items can be summed. The Development Team tracks this total work remaining at least for every Daily Scrum. The Development Team tracks these sums daily and projects 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 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.” It must be in useable condition regardless of whether the Product Owner decides to actually release it.
Definition of “Done”
When the 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 Meeting. 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. 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 Definition of “Done” will expand to include more stringent criteria for higher quality.
Scrum is free.
Scrum’s roles, artifacts, events, and rules are immutable and although implementing only parts of Scrum is possible, the result is not Scrum.
Scrum exists only in its entirety and functions well as a container for other techniques, methodologies, and practices.
- Scrum.org, Scrum Guide, The definite Guide to Scrum. The rules of Game (1991-2011 Ken Schwaber and Jeff Sutherland, All Rights Reserve)
- Scrum Team: Other sources speak of Roles. Scrum: a Breathtakingly Brief and Agile Introduction, 2012, Chris Sims & Hillary Louise Johnson