Define each function that the system is required to perform, how well the system, including its operators, is~required to perform that function, the conditions under which the system is to be capable
Systems Engineering | Specification | Applies Specification Processes and Procedures
Heading:5.5.3 Requirements Analysis Process
Reference:Standards Association of Australia 2003, Systems engineering - System life cycle processes, (AS NZS 15288-2003), Standards Australia, North Sydney.