Non-functional requirements describe the qualities or characteristics that the system should possess, such as performance, reliability, scalability, maintainability, usability, and security. Non-functional requirements are essential to ensure that the system operates correctly, safely, and efficiently under different conditions. For example, a non-functional requirement could be that the car’s airbag must deploy within 50 milliseconds of impact, or that the car must be able to maintain a minimum speed of 50 miles per hour for 10 minutes.
Performance requirements specify the speed, capacity, and throughput of the system, such as response time, processing speed, data transfer rate, and resource utilization. For car manufacturers, performance requirements can be related to the vehicle’s speed, acceleration, fuel efficiency, and more. These requirements ensure that the car performs optimally and meets the expectations of the customers.
Interface requirements specify how the system should interact with other systems or subsystems, such as protocols, data formats, and communication channels. For car manufacturers, interface requirements can relate to how different components of the car communicate with each other, such as the engine and transmission or the navigation system and entertainment system. These requirements ensure that the car operates efficiently and seamlessly.
Design requirements specify the constraints or criteria that the system design should meet, such as hardware or software specifications, standards, and best practices. In car manufacturing, design requirements can relate to safety standards, emissions regulations, or styling preferences. These requirements ensure that the car meets the necessary standards and regulations while also fulfilling the company’s design goals.
Maintenance requirements specify the procedures and activities required to maintain and support the system over its life cycle, such as updates, upgrades, repairs, and replacements. In car manufacturing, maintenance requirements can relate to servicing intervals, spare parts availability, and other maintenance needs. These requirements ensure that the car operates reliably and cost-effectively over its lifetime.
Test requirements specify the criteria and methods for testing the system, such as test cases, test procedures, and acceptance criteria. In car manufacturing, test requirements can relate to safety testing, emissions testing, and crash testing. These requirements ensure the car meets the necessary standards and regulations while also fulfilling the company’s design goals.
It is important to include information such as the requirement ID, description, priority, source, owner, status, and verification method when recording attributes for requirements. This information can help track and manage requirements throughout the system development process, ensuring that nothing is missed, and everything is tested and verified correctly.
In certain domains, such as automotive, aerospace, and medical devices, safety requirements form a critical aspect of the system design. Safety requirements specify the measures and controls that need to be implemented to ensure the system does not cause harm to its users or the environment. These cover aspects such as hazard analysis, risk assessment, fault tolerance, and fail-safe mechanisms. Compliance with safety requirements is often verified through various methods such as testing, analysis, and certification. For example, in the automotive industry, functional safety standards such as ISO 26262 require that the system is designed and tested to meet specific safety requirements.
In today’s digital age, security requirements are becoming increasingly important for any system that handles sensitive or confidential information. Security requirements cover aspects such as authentication, authorization, confidentiality, integrity, and availability. They ensure that the system is protected against various types of threats such as hacking, phishing, malware, and social engineering. Compliance with security requirements is often verified through various methods such as penetration testing, vulnerability assessments, and security audits.
Maintainability requirements specify the measures and controls that need to be implemented to ensure the system can be easily maintained and supported over its life cycle. Maintainability requirements cover aspects such as modularity, scalability, upgradability, and serviceability. Maintainability requirements ensure that the system can be updated, upgraded, repaired, and replaced without disrupting its normal operation. Compliance with maintainability requirements is often verified through various methods such as maintenance testing, field testing, and performance monitoring.
Separating requirements into different categories can help system engineers to organize and manage requirements more effectively, as well as ensure that all aspects of the system are covered by the requirements. System engineers can create a clear and concise set of requirements that can be used to guide the system development process by using a standard format for requirements, such as the “shall” statements for functional requirements, and by including information such as the requirement ID, description, priority, source, owner, status, and verification method. Moreover, system engineers can ensure that the system is designed and tested to meet specific safety and quality standards, such as ISO 26262 in the automotive industry, by paying attention to design and implementation constraints. Finally, system engineers can create a system that not only works as intended but also meets the needs and expectations of its users and stakeholders by including requirements for non-functional aspects such as performance, usability, security, and maintainability.
