Functional specification

Functional specifications. The functional specifications document, if created, defines functions and technological solutions that are specified for the computerized system based upon technical requirements needed to satisfy user requirements (e.g. specified bandwidth required to meet the user requirement for anticipated system usage).


The functional specifications provide a basis for the system design and configuration specifications. Functional specifications should consider requirements for operation of the computerized system in the intended computing environment, such as network infrastructure requirements, as well as functions provided by vendor-supplied software as well as functions required for user business processes that are not met by out-of-the-box software functionality and default configurations and that will require custom code development.

With regard to the proper functioning of computer software, the following general aspects should be kept in mind when specifying installation and user/functional requirements:

  • language, name, function (purpose of the programme)
  • inputs
  • outputs, including electronic data and metadata that constitute the “original records”
  • fixed set point (process variable that cannot be changed by the operator)
  • variable set point (entered by the operator)
  • edits (reject input/output that does not conform to limits and minimize errors)
  • input processing parameters (and equations)
  • programme overrides (e.g. to stop a mixer before time)

The personnel access roles who have the ability and/or are authorized to write, alter or have access to programmes should be identified. There should be appropriate segregation of roles between personnel responsible for the business process and personnel in system administration and maintenance roles who will have the ability to alter critical master data, critical set points, and system policies and configuration settings.

With regard to the proper functioning of computer hardware and to prevent damage, the following general aspects should be kept in mind when specifying installation and functional requirements:

  • location
  • power supply
  • environmental conditions
  • magnetic disturbances
  • mechanical disturbances
  • physical security