Functional and non-functional requirements need to be carefully selected in order to ensure that they make sense in the context of the final outcome of the project and conveyed to all the team members working on it. A functional requirement for an everyday object like a cup would be: “ability to contain tea or coffee without leaking”.

Typical functional requirements include:

• Business Rules

• Transaction corrections, adjustments and cancellations ,Administrative functions

• Authentication · Authorization levels · Audit Tracking· External
  Interfaces

Non-functional requirements: The definition of a non-functional requirement is: Any requirement which specifies how the system performs a certain function. In other words, a non-functional requirement will describe how a system should behave and what limits there are on its functionality.

Non-functional requirements generally specify the system’s quality attributes or characteristics, for example: “Modified data in a database should be updated for all users accessing it within 2 seconds. “Performance – for example: response time, throughput, utilization, static volumetric. Scalability, Capacity, Availability, Reliability, Recover-ability, Maintainability Serviceability, Security, Regulatory, Manageability, Environmental, Data Integrity, Usability and Inter-operability.