Wednesday, August 7, 2013


Understanding Non-Functional Requirements

Dearest Readers,

Requirements are the backbone of any Project and its a core competency of a Business Analyst to identify and document various Requirements correctly and completely. Its very important to understand and document Non-Functional Requirements along with the Functional Requirements, which do have an impact on the Project. In this blog post we will try to understand the so called Non-Functional Requirements and their categories.

What are Non-Functional Requirements (NFRs)?
NFRs specify ‘how’ the system should operate, rather than ‘what’ the system should do ‘functionally’. Examples include, but are not limited to, availability, reliability, capacity, scalability and security. These requirements are for a business system and address the aspects of the system that can possibly have a significant impact on how the system will work, and how it is accepted and operated both by the users and the people responsible for supporting and maintaining that system. 

The NFRs along with the functional requirements define the baseline against which the business system must be designed. It is essential that both sets of requirements are captured during the initial stages of a project. 

Non-Functional Requirements Categories:
NFRs define the Qualities expected in the system and the Constraints that may impact the system design and development.

The purpose of a non-functional requirements specification is:
  • To specify required properties of the system.
  • To define constraints on the system.
  • To facilitate early system sizing and estimation of cost.
  • To assess the viability of the proposed system.
  • To give a basis for designing the operational models.
  • To provide input to the component design.
The below diagrams depict various Categories of Non-Functional Requirements and respective Sub-Categories. 

Pic:  Non-Functional Requirements

The list of NFRs portrayed in the above list would help you guys to understand various categories of NFRs in your projects. Hope this will provide you all a glimpse of understanding NFRs. In the next blog-post I will provide a list of scenarios to document these NFRs for your project.

As We Work...We Learn...


Unknown said...

Hello, this is really helpful, do you have an XLS format you could publish or send me? thanks

Anonymous said...

Well explained in a short summary, with few good examples for each category.

Anonymous said...

This is indeed going to be helpful. Thanks. We can use the same to create a set of questionnaire for gathering NFR.

Direwolf said...

It is important to differentiate between NFRs and operational responsibilities (requirements) that need to documented in operation and maintenance document.

radha said...
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