There are two main types of requirements; functional and non-functional requirements. The success of any project depends on having accurate and detailed requirements in place. Inaccurate definition and documentation of requirements invariably leads to poor stakeholder communication, ongoing changes, and unnecessary delays. 9/10 major projects experience cost overrun. Poor requirements gathering is the top reason for overruns. Read more in our other blog ‘Requirements Gathering Top Reason for Overruns in Software Development.’
Functional requirements are a detailed list of features that describe what the system should do
Non-functional requirements, on the other hand, are constraints or qualities of a system such as performance, security, or usability.
Functional requirements in product management should not be confused with other types of requirements:
- Business requirements are high-level needs for the business, such as increasing customer lifetime value, decreasing customer churn, or gaining market share.
- User requirements, which describe the many objectives your users can accomplish with the product, are frequently defined as user stories, use cases, and scenarios.
- Product requirements outline how the system must function to satisfy the needs of the user and the business. They comprise both functional and non-functional requirements.
There are many advantages to documenting and coordinating on functional requirements:
- Clearly defined requirements helps to prevent misunderstandings by ensuring stakeholders, developers, designers, and testers remain on the same page and focused on the same objectives.
- The key measures of success of a technical project ais good communication by having clearly defined functional requirements it will aid meeting and make it easier to achieve goals.
- Estimation becomes more accurate as the team have a greater understanding of what the user wants.
- When Functional Requirements are fully explored during the discovery phase, then any assumptions, clarifications etc can be resolved early, which has shown to save time and money.
Functional requirements must be unambiguous, concise, and clear. Here are a few examples of effective functional requirements:
- Every time an order is placed, the system needs to send a confirmation email.
- Users of the blog system must be able to subscribe to the newsletter by providing their email.
- Users must be able to use their phone numbers to verify their accounts on the system.
It’s crucial to distinguish between functional and non-functional needs when gathering requirements.
Simply defined, functional requirements specify what the product should be able to accomplish, but non-functional requirements impose limitations on how it should be able to do it.
As the name suggests, functional requirements concern certain product functionality. Most of the time, defining, measuring, and testing them is an easy effort. Non-functional criteria, on the other hand, are more ethereal and are also referred to as “quality requirements” or “quality attributes.” They place restrictions on how the functional requirements can be implemented in terms of, performance, security, dependability, scalability and portability.
Functional requirements are often used to specify the quality attributes of a system or product, and are typically used to measure the overall performance and effectiveness of the system or product, rather than specific behaviours or functions. Examples of non-functional requirements include response time, throughput, availability, and security.
Conclusion
It is important to understand the difference between functional and non-functional requirements in order to successfully carry out the requirements gathering process. The requirements gathering process can be difficult and time consuming so it is best to use software to help.
Read our ‘Complete Guide to Requirements Gathering in 2023‘ for more!