What Is Non-Functional Requirements In Software Engineering ?

Imagine you’re buying a car. What features do you have in mind? Do you expect it to travel at 300 miles per hour and not to break down and fall apart? Can you include a sidecar to it or expand luggage space by attaching a pull-behind trailer? And let’s not forget about security systems in the car. While these requirements don’t directly describe the car’s primary function viz delivering a person from point A to point B – they are still extremely important to satisfy your needs as the driver.

Just like cars or any other kind of machinery, any software product or website or web application or a mobile/desktop app also has its own non-functional requirements which should have a set of quality attributes to meet their end-user needs.

SO, WHAT EXACTLY DOES A NON-FUNCTIONAL REQUIREMENT MEAN ?

Non-functional requirements in software engineering basically refer to the characteristics of a software system that are not related to specific functionality or behavior of the system. They describe how the system should perform, rather than what it should do.

WHAT ARE THE TYPES OF NON-FUNCTIONAL REQUIREMENTS ?

1. Performance : This non-functional requirement is related to the speed, scalability, and responsiveness of the system.A more simpler example of this requirement would be that the system should be able to handle a certain number of concurrent users or process a certain amount of data within a specific time frame.
2. Security: This  requirement is related to the protection of the system and its data from unauthorized access, as well as the ability to detect and recover from security breaches.
3. Usability: This requirement is related to the ease of use and understandability of the system for the end-users.
4. Reliability: This requirement is related to the system’s ability to function correctly,reliably as well as consistently under normal and abnormal conditions.
5. Maintainability: This requirement is related to the ease of maintaining the system, including testing, debugging, and modifying the system.
6. Portability: This requirement is related to the ability of the system to be easily transferred to different hardware or software environments.
7. Compliance: This requirement is related to adherence to laws, regulations, industry standards, or company policies.
8. Availability : This requirement is related to how available the system is at any point of time and also if the amount of downtime of the system is as low as possible
9. Localization : This requirement basically involves localizing the data of the system to the local region of the user

How VITAL ARE THE NON-FUNCTIONAL REQUIREMENTS TO THE WELL-BEING OF THE SOFTWARE SYSTEM ?

They are extremely important because they often can have a significant impact on the overall quality and success of a software system. They are  closely related to the system’s performance, security, and usability. They also help to ensure that the system is maintainable, portable, and compliant with relevant laws and regulations.

The Non-functional requirements can be imagined or seen as some kind of necessary rules or constraints imposed on the system. They deal with issues like scalability, maintainability, performance, portability, security, reliability, etc . If properly followed, the non-functional requirements ensure that the quality of the software system is not taken lightly as well as it improves the overall quality of the software if we properly follow all the non-functional requirements . If the Non-Functional Requirements are not addressed properly, the final outcome of the software system will include:

• All or majority of the users or clients as well as developers are unsatisfied with the final outcome of the system.
• Inconsistent and full of bugs in the software system
• The ultimate time and costs will overrun to fix the software which was prepared without keeping the non-functional requirements in mind.

One extremely important point to note is that often the non-functional requirements are interdependent and can affect each other. For example, a highly secure software system may have lower performance due to the additional security measures in place. Therefore, it is essential to carefully consider and balance the non-functional requirements when designing and developing a software system.

PROS OF NON-FUNCTIONAL REQUIREMENTS :

• They ensure the software system follows legal and adherence rules.
• They ensure the reliability, availability, performance, and scalability of the software system
• They help in constructing the security policy of the software system.
• They ensure good user experience, ease of operating the software, and minimize the cost factor.
• Improved system quality: By specifying non-functional requirements, engineers can ensure that the system will have desired characteristics such as performance, security, usability, reliability, maintainability, portability and compliance, which can improve the overall quality of the system.
• Increased user satisfaction: By ensuring that the system has good usability and meets the user’s performance and security expectations, engineers can increase user satisfaction with the system.
• Better alignment with business goals: By aligning non-functional requirements with the business goals, engineers can ensure that the system supports the overall objectives of the organization and meets the expectations of the stakeholders.
• Reduced rework: By identifying and addressing non-functional requirements early on in the development process, engineers can reduce the likelihood of costly rework later on.
• Improved system scalability and adaptability: By specifying non-functional requirements related to scalability and adaptability, engineers can ensure that the system can handle a growing number of users or changing business needs.
• Improved compliance: By specifying non-functional requirements related to compliance, engineers can ensure that the system adheres to relevant laws, regulations, industry standards or company policies.
• Better system maintenance: By specifying non-functional requirements related to maintainability, engineers can ensure that the system is easy to maintain, test and debug, which can save time and cost in the long run.

CONS OF NON-FUNCTIONAL REQUIREMENTS :

• The nonfunctional requirement may affect the various high-level software subsystem.
• They generally increase the cost as they require special consideration during the software architecture/high-level design phase.
• It is difficult to change or alter non-functional requirements once you pass them to the architecture phase.
• Difficulty in identifying all the requirements: It can be difficult to identify all the non-functional requirements, especially when dealing with complex systems or new technologies.
• Difficulty in predicting future requirements: It can be difficult to predict future non-functional requirements, which can result in the software becoming outdated or needing to be redesigned.
• Time-consuming: Gathering and specifying non-functional requirements can be time-consuming, which can slow down the development process.
• Costly: Identifying, specifying and implementing non-functional requirements can be costly, especially when involving multiple stakeholders.
• Risk of changing requirements: Non-functional requirements may change over time, which can lead to confusion and require additional work to keep the project aligned with the updated requirements.
• Conflicting requirements: Non-functional requirements may be in conflict with each other and it can be difficult to balance them and prioritize which one to implement.
• Unforeseen requirements: Non-functional requirements may not be fully identified during the requirement gathering phase, and some requirements may only be discovered after the system has been deployed.

SO, WHAT IS THE FINAL WORD ON NON-FUNCTIONAL REQUIREMENTS ?

Thus to conclude this article, non-functional requirements are indeed a critical aspect of software engineering that describe the qualities and characteristics of the software system beyond its functional requirements. These requirements ensure that the software system meets the expectations of its users and stakeholders and performs efficiently and reliably under different conditions and loads. Hence, as a project manager or product owner or CEO/CTO of an organisation, it is extremely important that along with the functional requirements of a system, you should adhere or follow and implement the non-functional requirements as well in order to ensure an amazing and success-full software system in the long-run of your career