Scrum Methodology in Agile Software Development
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===Scrum Master=== | ===Scrum Master=== | ||
| + | The scrum master worries that Scrum team can work without obstacles but he has no management authority over them. Essentially he has the aim to: | ||
| + | *create an environment to promote team self-organization; | ||
| + | *support team in the achievement of expected goals; | ||
| + | *ensure that events (e.g. daily Scrum meeting) take place in the right way; | ||
| + | *keep '''Scrum artefacts''' visible ('''Product Backlog''', '''Sprint Backlog''', '''Sprint burndown chart''' …); | ||
| + | |||
==Application== | ==Application== | ||
===Sprint=== | ===Sprint=== | ||
Revision as of 14:27, 21 September 2015
Today market is affected by uncertainly and sudden changes, in these conditions most of the models used in the 20th century to develop software are not still appropriate. Waterfall model , probably the most famous between them, is characterized by a stiff structure which can’t cope with the turbulent needs of actual market. In recent years many innovations are been enhanced in software engineering with a particular focus on the flexibility of these methods in order to cope with the customer’s and market’s needs; surely Agile Software Development is between them; ASD embraces the principles of lean production by applying them in software development to avoid waste and increase responsiveness to change. It represents the solution to the unpredictability of the market where the capacity to welcome change even late in development to satisfy customers is required. This article deals with Agile Software Development with a particular focus on one of its most used technique : Scrum Methodology.
Contents |
The big Idea
Scrum is an iterative method used to develop software, it can be placed inside the group of methods which are used in Agile Software Development. This word is taken from rugby and represents that phase of the match where an ordered formation of players, with arms interlocked and heads down, push forward against a similar group to gain possession of the ball. This method provides that work is divided into small chunks to manage complexity and to get early feedback from customers and end users; software development is carried out by small working team that allow rapid adjustment during the process and a quick delivery of the final product.
History: from Waterfall model to Agile Software Development
Waterfall model
In recent years customers are more and more unable to define their needs and at the same time their expectations from software are increased; they also require quick delivery and product already tested: with this assumptions traditional models are not able to face market demand.
Waterfall model, appreciated for its easy and clear way to manage a project, was the most used model in the last fifty years : its approach consists in the identification of five consequential steps (Requirements, Design, Implementation, Verification and Maintenance) through which it is possible to reach the end of the project; for every step they are defined requirements, objectives and timing to achieved them. This way of managing a project turned out unable to welcome customers’ changes because of stiffness of its structure which did not provide the flexibility that market needed.
Iterative model
A more flexible way of managing projects is provided by Iterative model from which ASD is derived. This method breaks the project into iterations of variable length, each producing a complete deliverable and building on the code and documentation produced before it. The activities of which every cycle is composed are based on the Waterfall model but thanks to the shorter length of each iteration this model is able to quickly react to any changes imposed by the customers.
Agile Software Development
Some practitioners believed that iterative model was not so responsive to changes that market required. They thought that to be Agile a process needs to accept change rather than stress predictability and that methods used to develop software has to respond to change as quickly as it arose rather than prevent changes.
It was in these circumstances that practitioners as Mary Poppendieck and Bob Charet started to take inspiration from Lean manufacturing principles and apply them to software development. These are the main points ,according to Poppendieck, which make Lean Production so successful and that can be applied to software development:
- elimination of waste that does not add value to the customer such as diagram and models that do not add value to the final deliverable;
- minimize inventory such as requirements and design documents;
- maximize flow by using iterative development to reduce development time;
- pull from demand;
- empower workers that means “tell developer what needs to be done not how to do it;
- meet customer requirements – work closely with the customer, allowing them to change their minds
- do it right the first time – test early and refactor when necessary;
- abolish local optimization – flexibly manage scope;
- partner with suppliers – avoid adversarial relationships, work towards developing the best software;
- create a culture of continuous improvement – allow the process to improve, learn from mistakes and successes. ( “Lean Software Development: An Agile Toolkit”, 2003 ).
Scrum methodology
There are two concepts that are at the basement of Scrum methodology: iterative development and team working. Developing in iterations allow Scrum team to adapt quickly to changing requirements, while working in close location and focusing on communication allow team to make decisions and act on them immediately rather than wait on correspondence.
Basically Scrum consists in a sequence of fixed-length iterations called Sprints managed by one or more cross-functional and self-organizing teams each composed by seven people that aim at a common goal and that usually work only on the software development. There are instead other two figures that manage all things that are in support of the development process: one is Product Owner who mainly handles customers contacts and the other is Scrum Master whose main task is to ensure that development team can work without obstacles.
Each sprint usually lasts from 2 to 4 weeks, in this period there are at least one meeting between the Product Owner and Development Team to define the main objectives; then there are short daily meetings held every morning to enhance communication and inform customers, developers, and managers on the status of the project, identify any problems encountered, and keep the entire team focused on a common goal.
Main figures in Scrum
Product Owner
Product owner is the link between customers and development team, he ensures that deliverables are in line with customers’ expectation and that stakeholders’ interests are fulfilled. He has also the task to fill out customer-centric items (typically user stories), ranks and prioritizes them before adds them to Product Backlog.
Usually development teams have only one Product owner, but differently from the Scrum master, he only takes care of the business side and does not interfere with the scrum team about the technological issues. At the beginning of each Sprint the Product Owner holds a Sprint Planning Meeting to state on which Product Backlog Items Scrum team will go to work during the next Sprint. In this phase he defines what are the most important items for that business, in according to customer’s needs.
Development Team
Development team task is to provide Product Backlog Items (PBIs) at the end of every Sprint in according with customers’ requirements after negotiating commitments with the Product Owner. Usually each team is composed by cross-functional members that allow an all-round software development; the main figures that there must be are a mix of software engineers, architects, programmers, analysts, QA experts, testers, and UI designers.
The size of the team is an important point, the group members' number influences capacity of people to communicate and work together: it is recommended that a scrum team is composed not more than nine people, usually seven.
Another important characteristic is the Self-organization of the group which facilitates members’ creativity and increases team cohesiveness: for this reason it is better to not change members of a team after they have worked together, especially if they had success in their project. After working together team members gain a mutual understanding that increases their capacity of team working, this synergy cannot be acquired if team are continuously changed.
A further point that characterized the good outcomes of a scrum team is location: people are most successful when located in the same room, particularly for the first few Sprints: this facilitates communication and information sharing.
Team self-organization
Team self-organization is a crucial point in the scrum methodology : with this concept it means that “it is told developer what needs to be done not how to do it”, they can autonomously choose the way to reach commitments. As it is said previously during Sprint execution, team members develop an intrinsic interest in shared goals and learn to manage each other to achieve them, for this reason self-organizing teams can radically outperform larger than traditionally managed teams. It has to be specified that an optimal self-organization takes time: it may be possible that for the first few sprints developers perform worse than when they work in the traditional way.
Some requirements are necessary to gain a good team self-organization:
- members are committed to clear, short-term goals;
- members can gauge the group’s progress;
- members can observe each other’s contribution;
- members feel safe to give each other unvarnished feedback.
Conversely there are some conditions that can hander self-organization:
- Geographical distribution: it is better if the whole team work in a room;
- Boss/work dynamics: each member has to consider the others as peer to facilitate a fair communication between them;
- Part-time team members;
- Interruptions unrelated to Sprint goals.
Scrum Master
The scrum master worries that Scrum team can work without obstacles but he has no management authority over them. Essentially he has the aim to:
- create an environment to promote team self-organization;
- support team in the achievement of expected goals;
- ensure that events (e.g. daily Scrum meeting) take place in the right way;
- keep Scrum artefacts visible (Product Backlog, Sprint Backlog, Sprint burndown chart …);
