Scrum is a feedback-driven empirical approach which is, like all empirical process control, underpinned by the three pillars of transparency, inspection, and adaptation. All work within the scrum framework should be visible to those responsible for the outcome: the process, the workflow, progress, etc. In order to make these things visible, scrum teams need to frequently inspect the product being developed and how well the team is working. With frequent inspection, the team can spot when their work deviates outside of acceptable limits and adapt their process or the product under development.
These three pillars require trust and openness in the team, which the following five values of scrum enable:
Commitment: Team members individually commit to achieving their team goals, each and every sprint.
Courage: Team members know they have the courage to work through conflict and challenges together so that they can do the right thing.
Focus: Team members focus exclusively on their team goals and the sprint backlog; there should be no work done other than through their backlog.
Openness: Team members and their stakeholders agree to be transparent about their work and any challenges they face.
Respect: Team members respect each other to be technically capable and to work with good intent.
The product backlog is one of the most important scrum artifacts. It is a breakdown of work to be done and contains an ordered list of product requirements that a scrum team maintains for a product. Common formats include user stories and use cases. The requirements define features, bug fixes, non-functional requirements, etc.—whatever must be done to deliver a viable product. The product owner prioritizes product backlog items (PBIs) based on considerations such as risk, business value, dependencies, size, and date needed.
The product backlog is what will be delivered, ordered into the sequence in which it should be delivered. It is visible to everyone but may only be changed with the consent of the product owner, who is responsible for ordering the product backlog items for the team to work on.
The product backlog contains the product owner’s assessment of business value and may include the team’s assessment of effort or complexity, often, but not always, stated in story points using the rounded Fibonacci scale. These estimates help the product owner to gauge the timeline and may influence the ordering of product backlog items; for example, if two features have the same business value, the product owner may schedule earlier delivery of the one with the lower development effort (because the return on investment is higher) or the one with higher development effort (because it is more complex or riskier, and they want to retire that risk earlier).
The product backlog and the business value of each product backlog item is the responsibility of the product owner. The effort to deliver each item may be estimated in story points, or time. By estimating in story points, the team reduces the dependency in individual developers; this is useful especially in dynamic teams where developers are often assigned to other projects after sprint delivery. For instance, if a user story is estimated as a 5 in effort (using Fibonacci sequence), it remains 5 regardless of how many developers are working on it.
Story points define the effort in a time-box, so they do not change with time. For instance, in one hour an individual can walk, run, or climb, but the effort expended is clearly different. The gap progression between the terms in the Fibonacci sequence encourages the team to deliver carefully considered estimates. Estimates of 1, 2 or 3 imply similar efforts (1 being trivial), but if the team estimates an 8 or 13 (or higher), the impact on both delivery and budget can be significant. The value of using story points is that the team can reuse them by comparing similar work from previous sprints, but it should be recognized that estimates are relative to the team. For example, an estimate of 5 for one team could be a 2 for another having senior developers and higher skills.
Every team should have a product owner, although in many instances a product owner could work with more than one team. The product owner is responsible for maximizing the value of the product. The product owner gathers input and takes feedback from, and is lobbied by, many people, but ultimately makes the call on what gets built.
The product backlog:
Captures requests to modify a product—including new features, replacing old features, removing features, and fixing issues
Ensures the developers have work that maximizes business benefit of the product
Typically, the product owner and the scrum team work together to develop the breakdown of work; this becomes the product backlog, which evolves as new information surfaces about the product and about its customers, and so later sprints may address new work.
Management
A product backlog, in its simplest form, is merely a list of items to work on. Having well-established rules about how work is added, removed and ordered helps the whole team make better decisions about how to change the product.
The product owner prioritizes product backlog items based on which are needed soonest. The team then chooses which items they can complete in the coming sprint. On the scrum board, the team moves items from the product backlog to the sprint backlog, which is the list of items they will build. Conceptually, it is ideal for the team to only select what they think they can accomplish from the top of the list, but it is not unusual to see in practice that teams are able to take lower-priority items from the list along with the top ones selected. This normally happens because there is time left within the sprint to accommodate more work. Items at the top of the backlog, the items to work on first, should be broken down into stories that are suitable for the team to work on. The further down the backlog goes, the less refined the items should be. As Schwaber and Beedle put it “The lower the priority, the less detail until you can barely make out the backlog item.
As the team works through the backlog, it must be assumed that change happens outside their environment—the team can learn about new market opportunities to take advantage of, competitor threats that arise, and feedback from customers that can change the way the product was meant to work. All of these new ideas tend to trigger the team to adapt the backlog to incorporate new knowledge. This is part of the fundamental mindset of an agile team. The world changes, the backlog is never finished.
Sprint backlog
The second important scrum artifacts is the sprint backlog is the list of work the team must address during the next sprint. The list is derived by the scrum team progressively selecting product backlog items in priority order from the top of the product backlog until they feel they have enough work to fill the sprint. The team should keep in mind its past performance assessing its capacity for the new-sprint, and use this as a guideline of how much ‘effort’ they can complete.
The product backlog items may be broken down into tasks by the developers. Tasks on the sprint backlog are never assigned (or pushed) to team members by someone else; rather team members sign up for (or pull) tasks as needed according to the backlog priority and their own skills and capacity. This promotes self-organization of the developers.
The sprint backlog is the property of the developers, and all included estimates are provided by the developers. Often an accompanying task board is used to see and change the state of the tasks of the current sprint, like to do, in progress and done.
Once a sprint backlog is decided, no additional work can be added to the sprint backlog except by the team. Once a sprint has been delivered, the product backlog is analyzed and reprioritized if necessary, and the next set of functionality is selected for the next sprint.
Increment
The increment is the potentially releasable output of the sprint that meets the sprint goal. It is formed from all the completed sprint backlog items, integrated with the work of all previous sprints. The increment must be complete, according to the scrum team’s definition of done (DoD), fully functioning, and in a usable condition regardless of whether the product owner decides to actually deploy and use it.
Extensions
The following artifacts and techniques can be used to help people use Scrum.
Sprint burndown chart
The sprint burndown chart is also another example of scrum artifacts. It is a publicly displayed chart showing remaining work in the sprint backlog. Updated every day, it gives a simple view of the sprint progress. It also provides quick visualizations for reference. The horizontal axis of the sprint burndown chart shows the days in a sprint, while the vertical axis shows the amount of work remaining each day (typically representing the estimate of hours of work remaining).
During sprint planning, the ideal burndown chart is plotted. Then, during the sprint, each member picks up tasks from the sprint backlog and works on them. At the end of the day, they update the remaining hours for tasks to be completed. In such a way, the actual burndown chart is updated day by day.
It should not be confused with an earned value chart.
Release burn-up chart
A sample burn-up chart for a release, showing scope completed each sprint (MVP = Minimum Viable Product), another example of the scrum artifacts that teams should be aware of.
The release burn-up chart is a way for the team to provide visibility and track progress toward a release. Updated at the end of each sprint, it shows progress toward delivering a forecast scope. The horizontal axis of the release burn-up chart shows the sprints in a release, while the vertical axis shows the amount of work completed at the end of each sprint (typically representing cumulative story points of work completed). Progress is plotted as a line that grows up to meet a horizontal line that represents the forecast scope; often shown with a forecast, based on progress to date, that indicates how much scope might be completed by a given release date or how many sprints it will take to complete the given scope.
The release burn-up chart makes it easy to see how much work has been completed, how much work has been added or removed (if the horizontal scope line moves), and how much work is left to be done.
Definition of ready (DoR)
The start criteria to determine whether the specifications and inputs are set enough to start the work item, i.e. a user story.
Definition of done (DoD)
The exit-criteria to determine whether a product backlog item is complete. In many cases, the DoD requires that all regression tests be successful. The definition of done may vary from one scrum team to another but must be consistent within one team.
Velocity
The total effort a team is capable of in a sprint. The number is derived by evaluating the work (typically in user story points) completed in the last sprint. The collection of historical velocity data is a guideline for assisting the team in understanding how much work they can achieve.
Spike
A time-boxed period used to research a concept or create a simple prototype. Spikes can either be planned to take place in between sprints or, for larger teams, a spike might be accepted as one of many sprint delivery objectives. Spikes are often introduced before the delivery of large or complex product backlog items in order to secure budget, expand knowledge, or produce a proof of concept. The duration and objective(s) of a spike are agreed by the team before the start. Unlike sprint commitments, spikes may or may not deliver tangible, shippable, valuable functionality. For example, the objective of a spike might be to successfully reach a decision on a course of action. The spike is over when the time is up, not necessarily when the objective has been delivered.
Tracer bullet
Also called a drone spike, a tracer bullet is a spike with the current architecture, current technology set, current set of best practices that result in production quality code. It might just be a very narrow implementation of the functionality but is not throwaway code. It is of production quality, and the rest of the iterations can build on this code. The name has military origins as ammunition that makes the path of the bullet visible, allowing for corrections. Often these implementations are a ‘quick shot’ through all layers of an application, such as connecting a single form’s input field to the back-end, to prove the layers connect as expected.
A sprint (also known as iteration or timebox) is the basic unit of development in Scrum. The sprint is a timeboxed effort; that is, the length is agreed and fixed in advance for each sprint and is normally between one week and one month, with two weeks being the most common.
Each sprint starts with a sprint planning event that establishes a sprint goal and the required product backlog items. The team accepts what they agree is ready and translate this into a sprint backlog, with a breakdown of the work required and an estimated forecast for the sprint goal. Each sprint ends with a sprint review and sprint retrospective, that reviews progress to show to stakeholders and identify lessons and improvements for the next sprints.
Scrum emphasizes valuable, useful output at the end of the sprint that is really done. In the case of software, this likely includes that the software has been fully integrated, tested and documented, and is potentially releasable.
Sprint Planning
At the beginning of a sprint, the scrum team holds a sprint planning event to:
Mutually discuss and agree on the scope of work that is intended to be done during that sprint
Select product backlog items that can be completed in one sprint
Prepare a sprint backlog that includes the work needed to complete the selected product backlog items
Agree the sprint goal, a short description of what they are forecasting to deliver at the end of the sprint.
The recommended duration is four hours for a two-week sprint (pro-rata for other sprint durations)
During the first half, the whole scrum team (development team, scrum master, and product owner) selects the product backlog items they believe could be completed in that sprint
During the second half, the development team identifies the detailed work (tasks) required to complete those product backlog items; resulting in a confirmed sprint backlog
As the detailed work is elaborated, some product backlog items may be split or put back into the product backlog if the team no longer believes they can complete the required work in a single sprint
Once the development team has prepared their sprint backlog, they forecast (usually by voting) which tasks will be delivered within the sprint.
Daily Scrum
A daily scrum in the computing room. This centralized location helps the team start on time.
Each day during a sprint, the team holds a daily scrum (or stand-up) with specific guidelines:
All members of the development team come prepared. The daily scrum:
starts precisely on time even if some development team members are missing
should happen at the same time and place every day
is limited (timeboxed) to fifteen minutes
Anyone is welcome, though only development team members should contribute.
During the daily scrum, each team member typically answers three questions:
What did I complete yesterday that contributed to the team meeting our sprint goal?
What do I plan to complete today to contribute to the team meeting our sprint goal?
Do I see any impediment that could prevent me or the team from meeting our sprint goal?
Any impediment (e.g., stumbling block, risk, issue, delayed dependency, assumption proved unfounded) identified in the daily scrum should be captured by the scrum master and displayed on the team’s scrum board or on a shared risk board, with an agreed person designated to working toward a resolution (outside of the daily scrum). While the currency of work status is the whole team’s responsibility, the scrum master often updates the sprint burndown chart. Where the team does not see the value in these events, it is the responsibility of the scrum master to find out why. This is part of the responsibility of educating the team and stakeholders about the Scrum principles.
No detailed discussions should happen during the daily scrum. Once the meeting ends, individual members can get together to discuss issues in detail; such a meeting is sometimes known as a ‘breakout session’ or an ‘after party’.
Sprint Review
At the end of a sprint, the team holds two events: the sprint review and the sprint retrospective.
At the sprint review, the team:
reviews the work that was completed and the planned work that was not completed
presents the completed work to the stakeholders (a.k.a. the demo)
collaborates with the stakeholders on what to work on next
Guidelines for sprint reviews:
Incomplete work cannot be demonstrated.
The recommended duration is two hours for a two-week sprint (proportional for other sprint-durations).
Sprint retrospective
At the sprint retrospective, the team:
reflects on the past sprint
identifies and agrees on continuous process improvement actions
Guidelines for sprint retrospectives:
Three main questions arise in the sprint retrospective:
What went well during the sprint?
What did not go well?
What could be improved for better productivity in the next sprint?
The recommended duration is one-and-a-half hours for a two-week sprint (proportional for other sprint duration(s)).
The scrum master facilitates this event.
Backlog refinement
Backlog refinement (formerly called grooming) is the ongoing process of reviewing product backlog items and checking that they are appropriately prepared and ordered in a way that makes them clear and executable for teams once they enter sprints via the sprint planning activity. Product backlog items may be broken into multiple smaller ones. Acceptance criteria may be clarified. Dependencies may be identified and investigated.
Although not originally a core Scrum practice, backlog refinement has been added to the Scrum Guide and adopted as a way of managing the quality of product backlog items entering a sprint, with a recommended investment of up to 10% of a team’s sprint capacity.
The backlog can also include technical debt (also known as design debt or code debt). This is a concept in software development that reflects the implied cost of additional rework caused by choosing an easy solution now instead of using a better approach that would take longer.
There are three roles in the Scrum framework. These are ideally co-located to ensure optimal communication among team members. While many organizations have other roles involved with defining and delivering the product, Scrum defines only these three.
Product Owner
The product owner role, representing the product’s stakeholders and the voice of the customer (or may represent the desires of a committee), is responsible for delivering good business results. Hence, the product owner is accountable for the product backlog and for maximizing the value that the team delivers. The product owner defines the product in customer-centric terms (typically user stories), adds them to the Product Backlog, and prioritizes them based on importance and dependencies. A scrum team should have only one product owner (although a product owner could support more than one team). This role should not be combined with that of the scrum master. The product owner should focus on the business side of product development and spend the majority of their time liaising with stakeholders and the team. The product owner should not dictate how the team reaches a technical solution, but rather will seek consensus among the team members. This role is crucial and requires a deep understanding of both sides: the business and the engineers (developers) in the scrum team. Therefore a good product owner should be able to communicate what the business needs, ask why they need it (because there may be better ways to achieve that), and convey the message to all stakeholders including the Development Team using a technical language, as required. The Product Owner uses Scrum’s empirical tools to manage highly complex work, while controlling risk and achieving value.
Communication is a core responsibility of the product owner. The ability to convey priorities and empathize with team members and stakeholders is vital to steer product development in the right direction. The product owner role bridges the communication gap between the team and its stakeholders, serving as a proxy for stakeholders to the team and as a team representative to the overall stakeholder community.
As the face of the team to the stakeholders, the following are some of the communication tasks of the product owner to the stakeholders:
Define and announce releases.
Communicate delivery and team status.
Share progress during governance meetings.
Share significant RIDAs (risks, impediments, dependencies, and assumptions) with stakeholders.
Negotiate priorities, scope, funding, and schedule.
Ensure that the product backlog is visible, transparent and clear.
Empathy is a key attribute for a product owner to have—the ability to put one’s self in another’s shoes. A product owner converses with different stakeholders, who have a variety of backgrounds, job roles, and objectives. A product owner must be able to see from these different points of view. To be effective, it is wise for a product owner to know the level of detail the audience needs. The development team needs thorough feedback and specifications so they can build a product up to expectation, while an executive sponsor may just need summaries of progress. Providing more information than necessary may lose stakeholder interest and waste time. A direct means of communication is the most preferred by seasoned agile product owners.
A product owner’s ability to communicate effectively is also enhanced by being skilled in techniques that identify stakeholder needs, negotiate priorities between stakeholder interests, and collaborate with developers to ensure effective implementation of requirements.
Development Team
The development team has from three to nine members who carry out all tasks required to build increments of valuable output every sprint.
While team members are referred to as developers in some literature, the term refers to anyone who plays a role in the development and support of the system or product, and can include researchers, architects, designers, data specialists, statisticians, analysts, engineers, programmers, and testers, among others. However, due to the confusion that can arise when some people do not feel the term ‘developer’ applies to them, they are often referred to just as team members.
The team is self-organizing. While no work should come to the team except through the product owner, and the scrum master is expected to protect the team from too much distraction, the team should still be encouraged to interact directly with customers and/or stakeholders to gain maximum understanding and immediacy of feedback.
Scrum Master
Scrum is facilitated by a scrum master, who is accountable for removing impediments to the ability of the team to deliver the product goals and deliverables. The scrum master role is not a traditional team lead or project manager but acts as a buffer between the team and any distracting influences. The scrum master ensures that the scrum framework is followed. The scrum master helps to ensure the team follows the agreed processes in the Scrum framework, often facilitates key sessions, and encourages the team to improve. The role has also been referred to as a team facilitator or servant-leader to reinforce these dual perspectives.
The core responsibilities of a scrum master include (but are not limited to):
Helping the product owner maintain the product backlog in a way that ensures the needed work is well understood so the team can continually make forward progress
Helping the team to determine the definition of done for the product, with input from key stakeholders
Coaching the team, within the Scrum principles, in order to deliver high-quality features for its product
Promoting self-organization within the team
Helping the scrum team to avoid or remove impediments to its progress, whether internal or external to the team
Facilitating team events to ensure regular progress
Educating key stakeholders on Agile and Scrum principles
Coaching the development team in self-organization and cross-functionality
The scrum master helps people and organizations adopt empirical and lean thinking, leaving behind hopes for certainty and predictability.
One of the ways the scrum master role differs from a project manager is that the latter may have people management responsibilities and the scrum master does not. A scrum master provides a limited amount of direction since the team is expected to be empowered and self-organizing. Scrum does not formally recognize the role of project manager, as traditional command and control tendencies would cause difficulties.
The software development term scrum was first used in a 1986 paper titled “The New New Product Development Game”. The term is borrowed from rugby, where a scrum is a formation of players. The term scrum was chosen by the paper’s authors because it emphasizes teamwork.
Scrum is occasionally seen written in all-capitals, as SCRUM. While the word itself is not an acronym, its capitalized styling likely comes from an early paper by Ken Schwaber that capitalized SCRUM in its title.
While the trademark on the term Scrum itself has been allowed to lapse, it is deemed as owned by the wider community rather than an individual so the leading capital for Scrum is retained in this article.
Many of the terms used in Scrum are typically written with leading capitals (e.g., Scrum Master, Daily Scrum). However, to maintain an encyclopedic tone, this article uses normal sentence case for these terms (e.g., scrum master, daily scrum) – unless they are recognized marks (such as Certified Scrum Master).
