Software requirements include three levels of requirements:
Business Requirement: Shows the organization or customer requirements for the high level of the system and product, explained by the project vision and scope documents.
User Requirement: Describes the tasks that the user has to do with the system and product, explained by the use-case document.
Functional Requirements and Non Functional Requirements: Functional Requirement defines the software functionality that the developer must implement, and the user completes their work and tasks through these functions to meet the needs of the business. Non Functional Requirements describes the attributes of the system, including quality attributes, operation interface, performance, constraints, standards and specifications that should be followed. Functional Requirements and Non Functional Requirements are explained by software requirements specifications and models.
Types of Software requirements
Relationships among several types of requirements information
