A Non-Functional Requirement (NFR) defines the quality attribute of a software system. They represent a set of standards used to judge the specific operation of a system. Example, how fast does the website load? 

A non-functional requirement is essential to ensure the usability and effectiveness of the entire software system. Failing to meet non-functional requirements can result in systems that fail to satisfy user needs. 

Non-functional Requirements allows you to impose constraints or restrictions on the design of the system across the various agile backlogs. Example, the site should load in 3 seconds when the number of simultaneous users are> 10000. Description of non-functional requirements is just as critical as a functional requirement. 

 

Types of Non-functional Requirement

 

• Usability requirement

• Serviceability requirement

• Manageability requirement

• Recoverability requirement

• Security requirement

• Data Integrity requirement

• Capacity requirement

• Availability requirement

• Scalability requirement 

• Interoperability requirement

• Reliability requirement

• Maintainability requirement

• Regulatory requirement

• Environmental requirement

 

Examples of Non-functional requirements

 

Here, are some examples of non-functional requirement: 

1. Users must change the initially assigned login password immediately after the first successful login. Moreover, the initial should never be reused.

2. Employees never allowed to update their salary information. Such attempt should be reported to the security administrator.

3. Every unsuccessful attempt by a user to access an item of data shall be recorded in an audit trail. 

4. A website should be capable enough to handle 20 million users with affecting its performance

5. The software should be portable. So moving from one OS to other OS does not create any problem.

6. Privacy of information, the export of restricted technologies, intellectual property rights, etc. should be audited.

 

Advantages of Non-Functional Requirement 

 

Benefits/pros of Non-functional testing are: 

• The nonfunctional requirements ensure the software system follow legal and compliance rules.

• They ensure the reliability, availability, and performance of the software system 

• They ensure good user experience and ease of operating the software. 

• They help in formulating security policy of the software system. 

 

Disadvantages of Non-functional Requirement 

 

Cons/drawbacks of Non-function requirement are: 

• None functional requirement may affect the various high-level software subsystem 

• They require special consideration during the software architecture/high-level design phase which increases costs. 

• Their implementation does not usually map to the specific software sub-system,

• It is tough to modify non-functional once you pass the architecture phase.

 

Summary

 

• A non-functional requirement defines the performance attribute of a software system.

• Types of Non-functional requirement are Scalability Capacity, Availability, Reliability, Recoverability, Data Integrity, etc.

• Example of Non Functional Requirement is Employees never allowed to update their salary information. Such attempt should be reported to the security administrator.

• Functional Requirement is a verb while Non-Functional Requirement is an attribute 

• The advantage of Non-functional requirement is that it helps you to ensure good user experience and ease of operating the software 

• The biggest disadvantage of Non-functional requirement is that it may affect the various high-level software subsystems.