Three levels of software requirements

software requirements are divided into three levels: business requirements, user requirements, and functional requirements .

1, Business needs (why): reflects the organization or the customer to the system, product high-level goal pursuit, defined the project's vision and scope, that is to determine the project's development direction, functional scope, target customers and value sources. Will form a " vision and scope document ".

2. User demand (what): describe what users can accomplish with this product. It is generally described in a combination of natural language and intuitive graphics, but care should be taken to avoid too vague a description and to consider the implementation. A " use case document " will be formed.

3. Functional requirements (how): indicate what the developer should do to enable the user to complete his task and then meet the business requirements. It is generally described as "should", such as: "The system should send an email informing the user that the subscription was successful." A " Software Requirements Specification " will be formed.

*, non-functional requirements: Description of system performance, effects, etc. Such as:

The ① system responds within 5s

② system can support 50 000 people simultaneously access

Three levels of software requirements