ANSWER

The Business Analysis Body of Knowledge® (BABOK®) defines the following levels of requirements:

• “Business Requirements are higher-level statements of the goals, objectives, or needs of the enterprise.  They describe things such as the reasons why a project is initiated, the things that the project will achieve, and the metrics which will be used to measure success.
• Stakeholder Requirements are statements of the needs of a particular stakeholder or class of stakeholders.  They describe the needs that a given stakeholder has and how the stakeholder will interact with the solution. Stakeholder Requirements serve as a bridge between Business Requirements and the various classes of Solution Requirements.
• Solution Requirements define the characteristics of a solution that meets the Business Requirements and Stakeholder Requirements. They are frequently divided, particularly when the requirements describe a software solution, into:
  • Functional Requirements describe the behavior and information that the solution will manage. They describe capabilities the system will be able to perform in terms of behaviors or operations – a specific system action or response.
  • Non-Functional Requirements capture conditions that do not directly relate to the behavior of functionality of the solution, but rather describe environmental conditions under which the solution must remain effective or qualities that the system must have.  They are also known as quality or supplementary requirements. 
• Implementation Requirementsdescribe capabilities that the solution must have in order to facilitate transition from the current state of the enterprise to the desire future state, but that will not be needed once the transition is complete” (Business Analysis Body of Knowledge® 2008).

• User requirements: are written for customer in natural language and simplified diagrams which describe system features and services.
• System requirements: are written as a contract between client and the contractor, and it is a structured document setting out detailed descriptions of the system services.
• Software specification: A detailed software description which can serve as a basis for a design or implementation and are written for developers.

• Business requirements: are written to represent the high level objectives and goal of the organization or stakeholders who want to build the system.
• User requirements: describe the user goal which the user desires from the new system.
• Functional requirements: specify the software functionality that the developers must build into the product to enable users to accomplish their tasks.

• High-level requirements: are written to specify the business the product is intended to support
• Business requirements: are written in a technologically neutral manner they specify what the product is to do for the work, not which technology is used to do it.
• Product's technological requirements: are written by designer who adds those requirements needed to make the product work in its technological environment.

• Stakeholder requests: are written in User language to capture all user requests.
• Features: are written to capture all feature of the system under development.
• Use cases: are written to capture functional requirements.
• Supplementary requirements: are written to capture Non-functional requirements (Leffingwell 1999).

References:

Business Analysis Body of Knowledge (version 2.0). 2008. International Institute of Business Analysis. pp 8-9.