Understanding Nonfunctional requirements

Requirements are defined as the conditions or statements which meet the demands of the clientele and the stakeholders. Requirements are documented in order to help the different teams to understand their responsibilities and organizations’ needs and the prospects. The business requirements are broadly classified as functional requirements and non-functional requirements.

Functional Requirements: The statements or conditions which are defined to satisfy the logical aspects of the software are covered under the functional requirements. These statements explain the different aspects of the application/software to be developed. These functional requirements are elicited during the requirement elicitation process headed by business analysts. The elicitation process is carried out in order to pull out the different angles associated with the requirements and to understand the viewpoint of different stakeholders. The most commonly used elicitation techniques are Interview, Brainstorming, Prototyping, reverse engineering, document-analysis and many others which are used as per the requirement and the comfort level of the business analyst or someone wearing the hat of the business analyst.

Nonfunctional Requirements: The statements or conditions which support the usage of the application or the software and which help in aligning the functional requirements are considered under the non-functional requirements. The non-functional requirements are defined to explain the different abilities  of the software developed. The non-functional requirements are also termed as non-behavioral requirements or quality attributes defined in order to support the quality analysts to approve the software against the different constraints which must be met. They define the overall attributes of the end product.

There is no definition to identify the difference between functional and non-functional requirements and there is a very thin line of difference between two categories. It entirely depends on the experience of the business analyst, details captured during the elicitation process and the constraints or limitations defined for the resulting product to categorize a certain set of requirements into functional or non-functional requirements. This thin line of differentiation between two categories sometimes doesn’t able to limit the functionalities to get categorized into two categories and there are certain conditions where a feature is captured in both functional and non-functional requirements using different expressions or syntax.

The different abilities or the checklist supporting the non-functional requirements are mentioned as below:

  • Availability: It defines the percentage availability of the system which is expected at the time of the system operations. The hardware capacity of the system is designed referring to this availability percentage of the software or application. The details are approved by the business owners and documented by the business analysts during the business requirement documentation.
  • Usability and Reusability: This defines the convenience by which the system can be used by the intended users. This ability of the system explains the capacity of the software to be learned, installed and used by the business users. How easily the users can be trained on the system defines the usability of the software. Some softwares are designed to be used for the development other systems which have common components. This capability is known as reusability of the software. A software is considered as well designed and developed if it can be used for other softwares with some common features.
  • Reliability: A software is authentic if the user can rely on the features of the software and its usage for longer duration. This feature of the software helps the organizations in choosing the product for their sensitive data. The demand of the product is directly proportional to the reliability of the software. The product or software is reliable if it’s also stable. The business owners prefer the stable product in order to get the higher availability of the same for the users.
  • Flexibility: There should be always a scope of the extension of the functionality within the developed product. This feature is known as flexibility. The software is designed in such a way that it should provide a room for expansion even after the deployment of the end product. The flexibility of the product depends on the design and techniques used for the development of the product and thus a business analyst has to take care of certain steps while finalizing the software design and development techniques.
  • Supportability: This feature of the software or the product is massively used during the maintenance phase. The ability to deploy new releases, alter the code, customization as per the users’ locations are covered under this feature. The customization of the product should not hamper the international usage and it should target the local users only.
  • Performance: How well the software performs at different timings for different number of users is defined under this capacity of the software. There is a common agreement on the performance of the software which is signed off at the time of BRD sign-off and it helps in designing the software and hardware structure of the product accordingly.

There are no proper methods present or followed by different business analysts in order to derive the non-functional requirements. This is because the abstraction level of the non-functional requirements are not similar to the functional requirements and for different softwares or products the set of non-functional requirements changes. Some nonfunctional requirements are difficult to define or express due to certain constraints which are evolved during the design and development and thus they are not included during the documentation process. As there are no guidelines or rules comparing with, the non-functional requirements are sometimes secluded or undermined which may result in the catastrophe during extensive usage of the software.

Different stakeholders have their own understanding and in turn requirements. This is also true in the case of the non-functional requirements. The stakeholders’ requirements thus should be catered separately and their needs should not be treated as a landmark while testing the non-functional requirements.

Nonfunctional requirements thus are treated as an important aspect while designing the software and these requirements should be analyzed, precisely measured and developed accordingly for the successful implementation of the software and usage of the end product.


Happy Reading!!!

3 thoughts on “Understanding Nonfunctional requirements”

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  2. Hi Aniket,

    Very helpful and compact website. Thank you for bringing everything together. Very helpful it was!

    I need your help on ‘technical scope documentation’. can you share any sample if you have or information.

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