Requirements Elicitation and Specification


Elic… what? that sounds complicated. Well, it actually isn’t. I’ve talked about functional and non-functional requirements before, but this is something completely different.

As you may remember, the first step of the SDLC is collecting infomation, requirements elicitation and specification are part of this step.

Requirement elicitation, is actually the first thing you have to do in the software life-cycle and is the practice of finding out what the customer or user wants. In an informal concept, is more like a wish list of requirements. But there are many problems that are almost impossible to avoid because it depends more of the customer, for example: he doesn’t know exactly what he wants, he thinks that some specifications are obvious or his needs changed and want the software to do something else.

Requirements elicitation practices include:

  • Interviews
  • Questionnaires
  • User observation
  • Workshops
  • Brainstorming
  • Use cases
  • Role playing
  • Prototyping

Once you know what the customer wants, you’ll be able to do the software requirement specification (SRS), which is a process of recording the client’s requirements in any form, like a document, a graphical representation, a graph, a pie, a cake, brownies, etc.

SRS also contains the functional and non-functional requirements and other specification types, for example: performance, maintainability, reliability, resource, etc.



Functional and non-functional requirements

A functional requirement is something the product needs to work, perform an action and fulfill the purpose. It answers the question of “What does it do?”. They describe the minimal requirements of the product functionality. A non-funtional requirement is something that the product have to increase it quality. It answers the question of  “How does it do it?”. Non-functional requirements are extras made to improve the functionality of the product.

To be more precise, in software engineer, functional requirements define the functions of the system, is the description of the feature required. It also includes description of the required functions. Some examples of functional requirements are calculations, technical details, data manipulation and processing.

Non-Functional requirements focus on quality factors and effectiveness. These factors are what give value to the software and make the functional requirements function appropriately.


Some non-functional requirements may be:
1. Usability
2. Availability
3. Reliability
4. Flexibility
5. Supportability
6. Performance

References: (2016). Functional and Non-Functional Requirements. [online] Available at: [Accessed 13 Sep. 2016].

SearchSoftwareQuality. (2016). Functional vs non-functional requirements, what is the difference?. [online] Available at: [Accessed 13 Sep. 2016].