Non-Functional Requirements in Software Engineering

Research indicates that erroneous requirement collecting is one of the main causes of up to 70% of project failures. However, the real issue lies underlying that statistic: Teams tend to overlook non-functional factors in favour of functional needs or what the system does.

Non-functional requirements ensure that your product operates at a level that meets the expectations of your stakeholders, clients, and consumers and that you offer a positive user experience.

Too many product teams overlook non-functional requirements (NFRs) until it is too late. Even worse, it might completely blow your budget to update NFRs after your program has been built. According to some statistics, businesses lose anywhere from $400,000 to $94 million annually due to needless revision of requirements and code!

What is Non-Functional Requirements?

Non-functional Requirements (NFR) describe a software system's quality aspect. They evaluate the software system according to non-functional criteria essential to its success, such as portability, security, responsiveness, and usability. An example of a nonfunctional need might be "How quickly can I load the website?" Systems that don't fulfil user demands might result from not meeting non-functional criteria.

In software engineering, non-functional requirements allow you to place limitations or limits on the system's design throughout the different agile backlogs. For instance, the website should load in three seconds if over 10,000 people are logged in simultaneously. Just as important as a functional requirement's description is one for non-functional needs.

Various kinds of Non-Functional Needs

1. Performance

The most crucial non-functional requirement quality is system performance, which also influences practically all other needs.

Moreover, RAM features—reliability, availability, and maintainability—only satisfy these prerequisites. The speed at which a system can react to an action from a specific user while facing a given workload is called system performance.

2. Reliability

The likelihood and percentage that the program will function flawlessly for a given number of usage or duration of time is known as reliability.

3. Availability

This feature establishes how long the system runs, how long it takes to fix a bug, and how long it takes between errors.

4. Maintainability

This feature shows how quickly, easily, and on average, a system can be recovered following a breakdown.

5. Recoverability

Recoverability is the ability to recover from a crash or a malfunction in the system and return to full functioning.

6. Capacity

This feature shows the storage capacity of your system, which varies based on its type and specifications.

7. Serviceability

This feature shows how simple it is to do maintenance when needed.

8. Security

Security methods guard your software from hacking or espionage. Even stand-alone systems need these characteristics since you don't want unauthorized people to access your private information.

9. Manageability

The capacity to effectively manage and maintain a system's full functionality is the definition of this characteristic.

10. Environmental

These elements relate to the environment of the software. Will the system have to run all the time? What outside variables might have an impact on it? (as in snow, rain, and relative humidity.)

11. Data integrity

Ensuring and preserving data correctness and consistency over its whole lifespan is known as data integrity. A database mistake causes data loss if this factor is tainted.

12. Interoperability

To communicate data, all system components must adhere to a common set of exchange formats; noncompliance with these standards results in a lack of interoperability.

13. Usability

Users are concerned about this feature since it shows how well they can pick up and operate a system.

Non-Functional Requirements Examples

Examples of non-functional requirements are as follows:

  1. Immediately following their first successful login, users need to update the password they were originally provided. Additionally, the original should never be used again.
  2. Workers are never permitted to change their pay details. The security administrator should be notified of such an attempt.
  3. Whenever a user tries to access a piece of data but cannot, it gets documented on an audit trail.
  4. A website should be able to accommodate 20 million visitors without experiencing any performance issues.
  5. Portability is a must for the programme. Thus, switching between operating systems does not present any issues.
  6. Information privacy, exporting limited technology, intellectual property rights, etc., should all be audited.

Benefits of Non-Functional Requirement

  1. The non-functional criteria guarantee that the software system complies with applicable laws and regulations.
  2. They guarantee the software system's dependability, accessibility, and functionality.
  3. They provide an easy-to-use interface and a smooth software experience.
  4. They contribute to the creation of the software system's security policy.

Drawbacks of not having a Functional Need

  1. Non-functional requirements might have an impact on several high-level software subsystems.
  2. They need particular attention in the software architecture/high-level design stage, which drives up expenses.
  3. Typically, their implementation is not aligned with the particular software sub-system.
  4. Non-functional components are difficult to adjust after the architectural phase.