Functional vs. Non-Functional Requirements: Which Ones Do You Really Need?

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Software requirements are a crucial part of any development process. This is how decision-makers share their ideas and vision with the development team.  Misunderstandings between key actors and poor planning often contribute to a high-risk environment in software development and, as a consequence, a failed product or even business.

There’s the market and target audience analysis, and then there are software requirements, divided into the functional and non-functional ones. Failure to succeed in any of these will make the team run in circles, plugging holes, burning cash, and redesigning stuff on the go. Let’s dig deeper into the requirements and see how they can help the product thrive.

What Are Functional and Non-Functional Requirements?

Software requirements are presented as a text document, validated by both the decision-makers and the development team, to avoid any misunderstandings in the future. Despite both being fairly the same when it comes to setting and documenting them, these two types cover the project on very different levels. Here’s how.

Functional requirements focus on specific, to-the-point parameters. It essentially describes what functionality you want inside.

The list of the functional requirements vastly depends on the product, as each piece of software has its vision and mission. Some of the most common lists may include:

  • Basic customer journey
  • Transaction processing
  • Legal specifics
  • User authorization
  • Data tracking and security

Each point is later divided into smaller sub-points, describing what the product should include. Functional requirements provide answers to the following questions:

  • “What do we want to see inside the product?”
  • “What does the user need to use the product correctly?”

Non-functional requirements cover less concrete aspects of the product, mainly the expected performance of the product. These requirements also rely heavily on the product niche, market needs, user expectations, etc. Some of the metrics are:

  • Usability
  • Reliability
  • Scalability
  • Security
  • Performance

Product vision dictates many non-functional requirements, and your product may have unique circumstances and customer expectations. Here are some examples of how non-functional requirements may sound in real life:

  • “The system should process the search queries in less than 2 seconds”
  • “Our product has to be easy to scale internationally”
  • “The database should handle the information from more than 10,000 users”

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Benefits of Functional and Non-Functional Requirements

As any other preparatory step in the Software Development Lifecycle (SDLC), requirements gathering is aimed at eliminating risks and ensuring a controlled process. Let’s take a closer look at the advantages that software requirements can offer.

Shared vision

Defined and validated requirements help to share the product values and vision among the team members and to understand the end goal.

Communication clarity

Requirements lists allow quick and efficient progress tracking, expectations management, scope management, and efficient collaboration in general.

Validated roadmap

Requirements help see the project’s scope, set initial milestones, and define critical functionality and quality attributes. This way, the team can choose the optimal course of action and realistic timeframes.

Reduced spending

Developing a project without defined requirements is almost a guaranteed way to go over budget and risk the potential success of the whole endeavor. A concise playbook helps to move through each milestone and keep track of progress.

Correct technology stack

Establishing primary requirements early on helps choose the most fitting technology for the task. Not only can it affect the product performance but also the time and cost of the project.

Pleasant user experience

Meeting non-functional requirements is critical for making a product that users enjoy. Guided by one or more metrics described above, the team can refine the whole experience to meet the target audience’s expectations.

The Takeaway

Functional and non-functional requirements are the backbone of a successful development process.

Functional requirements describe what the product should include. Detailed lists help manage scope, budget, milestones, and much more, helping the team to develop the product within the budget and set targets.

Non-functional requirements are sometimes considered less important, but user experience heavily depends on meeting these conditions. They describe what the user expects to see from a product like yours, and the chances of success greatly increase if those expectations are met.

Overall, documented and validated requirements are a good way to ensure that product development stays on track and is flexible enough to respond to ongoing challenges and production issues.