Extreme Programming (XP) and Scrum are both popular in agile software development. Technically, XP is a methodology while Scrum is a framework. While they share some similarities, they are subtly different in what they try to achieve and how they are implemented.
- Extreme Programming (XP): XP is a software development methodology developed by Kent Beck intended to improve software engineering practices. It focuses on the technical aspects of development, such as coding, testing, and continuous integration. The key emphasis with XP is on the development team.
- Scrum: Scrum is a framework that has a slightly larger scope and focuses on project management and team collaboration. It provides a set of guidelines and roles to manage and deliver complex projects. Like XP, there is an emphasis on the development team, but Scrum takes things further by providing a framework for managing work through the use of backlogs and additional roles in the Scrum Master and Product Owner.
Roles and Responsibilities
Extreme Programming (XP): XP teams typically consist of developers, a customer representative, and a coach. The customer representative provides business requirements and feedback, while the coach facilitates the adoption of XP practices.
Scrum: Scrum teams have three primary roles: the Product Owner, the Scrum Master, and the Development Team.
- The Product Owner defines the product backlog and prioritizes items.
- The Scrum Master facilitates the Scrum process and coaches the team.
- Development Team is responsible for delivering the product increment.
Iterations and Planning
Extreme Programming (XP): XP employs short development cycles called iterations or sprints, typically lasting one to two weeks. Planning is done on a just-in-time basis, where requirements are prioritized and addressed as needed. The customer can request changes to the sprint and the team generally welcomes the changes. As long as the team has not started on the work, the iteration can change.
Scrum: Scrum also uses iterations called sprints, usually lasting two to four weeks. Sprint planning involves determining which items from the product backlog will be addressed during the sprint, and creating a sprint backlog with the tasks required to complete those items.
The Product Owner manages the Product Backlog which is a backlog of User Stories from the business. Once the PO completes the items in the Product Backlog, the Scrum Master or team representative pulls them into a sprint for work. While the sprint backlog is relatively short and represents only what can be accomplished in one sprint, the product backlog can be much more extensive as it represents items that are still being defined by the business.
Documentation and Development Practices
Extreme Programming (XP): XP favors minimal documentation. The focus is on code and frequent communication among team members, rather than comprehensive documentation.
XP promotes several technical practices, including test-driven development (TDD), continuous integration and delivery (CI/CD), pair programming, and frequent refactoring. These practices aim to ensure code quality and improve collaboration.
Scrum: Similar to XP, Scrum doesn't enforce heavy documentation. It encourages maintaining a product backlog, sprint backlog, and any necessary artifacts that aid in the project's transparency and communication.
Scrum does not prescribe specific software engineering practices. Instead, it allows teams to choose their preferred development methods. Scrum focuses on empowering the team to self-organize and deliver value in each sprint. Teams might choose to program in pairs and use DevOps principles, but that is up to them as Scrum dos not outline how the dev team should work.
Conclusion
Both XP and Scrum are flexible methodologies (frameworks) that can be adapted to suit the needs of a particular project or team. The choice between the two depends on factors such as project complexity, team size, and the desired level of focus on software engineering practices versus project management. In practice, many organizations choose to use a combination of the two to accomplish their complex software project goals.
