Functional and Non functional requirements – Examples and Differences


Functional and Non functional requirements

Functional and Non functional requirements of any software products are described below :

 

 Functional Requirements

Functional requirements are those requirements which deal with what the system should do or provide for users.

  • Describes the behavior of the system as it relates to the system’s functionality.
  • Includes the description of the required functions, outlines of associated reports or online queries, and details of data to be held in the system.
  • Specified by users themselves.

Non Functional Requirements

Non functional requirements are those requirements which elaborate the performance characteristic of the system and define the constraints on how the system will do so.

  • Defines the constraints, targets or control mechanisms for the new system.
  • Describes how, how well or to what standard a function should be provided.
  • Specified by technical peoples e.g. Architect, Technical leaders and software developers.
  • They are sometimes defined in terms of metrics (something that can be measured about the system) to make them more tangible.
  • Identify realistic, measurable target values for each service level.
  • These include reliability, performance, service availability, responsiveness, throughput and security.

 

Example of Functional and non functional requirements

If you are developing a Library system for your college, then the functional requirements can be listed as:

Membership facility
Issue of new books
Return of books
Member’s data
Visiting Books status
Pre booking of books

And the non functional requirements can be listed as:

Throughput
Service availability
Security of the system and
Reliability of the system

 


Difference between the functional and non functional requirements :

 

 

Functional Requirements

 

Non-Functional Requirements
1. Functional requirements are those         requirements that deal with what the system should do or provide for users.

 

1. Non-functional requirements are those requirements that define the constraints on how the system will do so.
2. It determines the product features.

 

2. It determines the product properties.
3. It is defined by the users. 3. It is determined by the software developers and architects.
4. It is easy to test the functional requirements. 4. It is comparatively difficult.

 

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A Soon-to-be Computer Engineer by profession, he has profound devotion to add Data Scientist as a prefix to his name. He’s been to the nooks of the web (at least of the surface web) and planning to add some real figures in his pocket!

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