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Software Engineering: SCRUM vs. XP
Last updated: May 9, 2023
1. Introduction
Agile software development is a methodology that weighs flexibility, iteration, and teamwork between cross-functional parties. It is based on the Agile Manifesto, a set of guiding values and principles for software development. Further, it promotes adaptive planning, evolutionary development, early delivery, and continuous improvement.
Moreover, Agile software development aims to provide working software incrementally by prioritizing customer value and embracing change. Thus, Agile approaches are commonly used in software development to deliver high-quality products and respond quickly to changing customer needs.
In this tutorial, we’ll elaborate on two Agile-based frameworks: Extreme Programming (XP) and Scrum.
2. Agile
Agile is a project management and product development approach that emphasizes flexibility and collaboration. It’s an incremental and iterative approach used to manage projects and deliver outcomes. The Agile methodology was first defined in the Agile Manifesto, a document created in 2001 by a group of software developers. The Agile approach is based on the following principles:
- Individuals and interactions over processes and tools
- Working software over comprehensive documentation
- Customer collaboration over contract negotiation
- Responding to change by sticking to the plan
The Agile approach is often implemented using Scrum, which is a specific framework for managing and completing projects using the Agile methodology. Although there exist other Agile-base frameworks like Lean development, Crystal, Kanban, or mentioned XP.
Agile is widely used and popular in the IT industry. On the other hand, it’s now been adopted in other industries as well, such as marketing, finance, and healthcare, due to its flexibility and ability to adapt to changing requirements. Agile methodology helps teams to deliver working software in short cycles and to be more responsive to the changing needs of the customers and stakeholders.
3. Scrum
Agile approaches are commonly used in software development to deliver high-quality products and respond quickly to changing customer needs. It’s an Agile-based framework that is widely used in software development and other industries. Scrum is based on three main components: roles, ceremonies, and artifacts.
The Scrum framework includes roles such as the Product Owner, Scrum Master, and Development Team. Further, it defines ceremonies such as Sprint Planning, Daily Scrum, Sprint Review, and Sprint Retrospective. Scrum aims to deliver an MVP (minimum viable product) at the end of each iteration called sprint. Each sprint should add value to the developed project.
Scrum allows teams to deliver working software in short cycles, and to be more responsive to the changing needs of the customers and stakeholders. It encourages collaboration, adaptability, and continuous improvement, and has proven to be effective in many industries. In the following, we’ll elaborate on the most important Scrum components: roles, ceremonies, and artifacts:
3.1. Roles
In Scrum, there are three main roles: Product Owner, Scrum Master, and Development Team.
The Product Owner is responsible for defining the goals and objectives of the product, as well as maintaining the product backlog. The Product Owner is the main point of contact between the team and external stakeholders.
The Scrum Master is responsible for ensuring that the Scrum rules are followed, as well as resolving any problems and conflicts that may arise within the team.
The Development Team consists of members responsible for creating the product. The team is responsible for achieving the goals and objectives of the product, as well as creating a potentially releasable product at the end of each sprint.
These are the main roles in Scrum, but depending on the project and organization, other roles may appear. In Scrum, all team members are responsible for the success of the project as well as for its failure.
3.2. Ceremonies
In Scrum, there are four main ceremonies: Sprint Planning, Daily Scrum, Sprint Review, and Sprint Retrospective.
Sprint Planning begins at the beginning of each sprint and aims to define the goals and tasks for the upcoming sprint. The Development Team and Product Owner meet to discuss and plan the work for the upcoming sprint.
The Daily Scrum is a short daily meeting where the Development Team discusses progress and planning for the upcoming day. It’s an opportunity to respond quickly to any issues and conflicts that may arise during the sprint.
The Sprint Review takes place at the end of each sprint. During it, the Development Team demonstrates their accomplishments and progress to the Product Owner and other stakeholders. The goal is to discuss what was done and what’s next.
The Sprint Retrospective also takes place at the end of the sprint, where the Development Team discusses what went well and what needs to be improved in the next sprints. The goal is to improve the process and work of the team continuously.
3.3. Artifacts
There are three main artifacts in Scrum: Product Backlog, Sprint Backlog, and Product Increment.
The Product Backlog is a list of all the tasks and functionalities that must be completed to achieve the product goals. It is a dynamic list that the Product Owner constantly updates.
Sprint Backlog is a list of tasks that the Development Team commits to complete in a given sprint. It is a list that is created during the Sprint Planning ceremony and is updated during daily Scrum meetings.
The Product Increment is an outcome of the current Sprint added to the value generated during all previous Sprints.
These artifacts are essential to the proper functioning of Scrum and help the team focus on the goals and objectives of the product.
4. Extreme Programming (XP)
Extreme Programming (XP) is a project management method developed by Kent Beck in the 1990s. XP aims to increase software efficiency and quality through continuous testing and refactoring of code. Moreover, XP focuses on the needs of the customer, the team, and the software development process. The method consists of 12 principles, which are the foundation for how it works.
In XP, it is important to constantly adapt to changing customer needs and focus on simple solutions. Thus, Extreme Programming is a method that focuses on the quality of the software and the needs of the customer. Therefore, it allows for continuous project development and adaptation to changing needs.
4.1. Principles
XP is based on 12 principles that underpin the methodology. These are:
- Listening to the customer: the team should constantly listen to the customer’s needs and adapt their activities to their changing needs
- Simple things first: the team should focus on the most important and simplest things before moving on to more complex tasks
- Working in tandem: working in tandem allows us to increase efficiency and code quality by constantly exchanging ideas and controlling code quality
- Unit testing: XP assumes that every piece of code should be covered by unit tests, which allows for easier error detection and facilitates code refactoring
- Refactoring: continuous refactoring keeps the code clean and simple, making it more readable and easier to develop
- Design on the fly: software design should be a continuous process and adapt to customer needs and changing conditions
- Continuous integration: continuous integration allows for quick error detection and enables continuous software development
- Continuous delivery: XP’s premise is that software should be delivered to the customer in continuous, small iterations. Therefore, allows for rapid response to customer needs and changing conditions
- Code-focused teams: the team should focus on the code and its quality to increase the efficiency and quality of the software
- Quality control: XP implies continuous quality control of the code through unit tests and automated tests, which allows for quick detection of errors
- Responsible teams: the team should be responsible for the entire project, from planning to delivering the software to the customer
- In touch with reality: the team should constantly monitor reality and adapt its actions to changing conditions
4.2. Process
The Extreme Programming process consists of several steps that allow the team to develop and customize the software continuously. In the first place, the team plans what it wants to achieve in the next iteration and determines what functionality will be needed to meet the goals. Further, the team analyzes the client’s needs and develops a requirements specification for the software.
Then, the team designs the structure of the software and determines the tools and technologies needed to implement it. Consequently, implementing the code, testing it with unit tests, integrating it with other pieces of software, performing the continuous refactoring, system, and acceptance testing, and delivering the software to the client occurs.
Lastly, the team conducts a retrospective to assess what things went well and what didn’t, and what can be improved in the future. Altogether, all of these steps are done in small iterations, allowing the team to constantly adapt to the customer’s needs and respond quickly to changing conditions. Below we can see a chart presenting an XP process flow.
5. Comparison
First of all, both Scrum and XP aim to deliver a high-quality product to the client as fast as possible. Although Scrum focuses on management and productivity, whereas XP concentrates on software quality and engineering techniques.
Secondly, frameworks have few differences when it comes to Sprints. Sprint in Scrum usually lasts longer, about 2-4 weeks. While XP emphasizes shorter Sprints, usually lasting 1-2 weeks. Moreover, during Scrum’s Sprint, no changes are allowed to interrupt Sprint’s target. On the other hand, XP is more flexible, and customers can add changes during Sprint.
Thirdly, prioritizing tasks occurs in different ways. In Scrum, the Product Owner, with communication with the Development Team, is responsible for priorities. In contrast, using XP, developers implement tasks in strict priority order.
Finally, both frameworks affirm different values. Scrum relies on openness, focus, and commitment. However, XP depends on communication, simplicity, and feedback.