Types and Specifications of Functional and Non-Functional Requirements

Home Articles Types and Specifications of Functional and Non-Functional Requirements

The predefined requirements are the basic signs that lead a project to its successful completion. It establishes a formal agreement between the client and the provider who are trying to achieve a similar goal. Detailed and high-quality requirements also help in mitigating monetary risks and keep the tasks within specified schedule.

Classification of Requirements

Stakeholders Requirements: The requirements of discrete stakeholders’ packages are defined in more detail to characterize what they expect from a project.

Business Requirements: These include high-level statements of objectives, goals, and requirements.

Solution Requirements: The requirements with respect to the agreements present the attributes that the product must solve the problems of the stakeholders and the company itself.

Non-functional requirements have general attributes of the system. They are called as qualitative attributes.

Functional Requirements show how a product should function along with its advantages and possibilities.

Specifications of Functional Requirements

Functional requirements are the most important attributes or capabilities that engineers must implement into the project so that customers can perform their tasks effectively. Therefore, it is essentially important to make it clear for the stakeholders as well as the development teams. In general, the requirements show the behaviour of frames under clear conditions.

Generally, requirements are recorded in the content, especially in the case of Agile-driven projects. However, they can also be visuals. Here are the most known documents and common formats:

  • SRS (Software Requirements Specification) documents
  • User Stories
  • Use cases
  • Structure of work breakdown (WBS)

Non-Functional Requirements

Non-functional requirements present how the system should work and limit its usefulness. Such requirements are known as quality attributes of the system.

Some of the non-functional requirements of the project are described below:


Usability defines how difficult it will be for the client to learn and work with the product. With the help of system efficiency and low perceived workload, system usability can be defined in an effective manner.


Reliability defines the likelihood that the product will work without failure for a given period of time. Reliability decreases as a result of code errors, hardware failures or problems with other parts of the system. To evaluate the reliability of software, one can verify the level of the actions that were completed or track a normal time-period of the system runs before its failure.


The requirements for Scalability demonstrate how system must evolve without affecting their performance. This means serving more customers, managing more information and making more transactions. Scalability has both equipment and programming suggestions. For example, one can increase Scalability by including memory, servers, or disk space. On the other hand, one can use compressed data, optimizing algorithms, etc.


Security requirements ensure that the product is protected against unapproved access to the framework and stored information. Consider the different dimensions of approval and validation in various roles of the users.


Performance is a qualitative characteristic that represents the responsiveness of the system during several interactions with the client. Poor performance results in a negative experience for the client. It also threatens the system when it is overloaded.


Availability is measured by time frame in which usability and system services are available for all tasks. The schedules maintenance intervals directly influence this parameter. In addition, it is important to determine how the impact of the maintenance can be limited. When writing availability requirements, the team must characterize the most basic segments of the system that must be available in an incomparable way.