Approaches for Early or Rapid measurement

The COSMIC method provides a standardized way of measuring a functional size of software from the domains commonly referred to as ‘business application’ (or ‘MIS’), ‘real-time’ and infrastructure software, certain types of scientific/engineering software and hybrids of these. In practice it is sometimes sufficient or necessary to measure a functional size approximately . Typical situations where such a need arises are:

  • early in the life of a project, before the requirements have been specified in detail
  • when a size measurement is needed, but there is insufficient time or resources
  • when the quality of the documentation of the actual requirements is not good enough

The purpose of this new Guideline is to describe the current state of the art with regard to early or rapid COSMIC functional size measurement using approximation approaches. All proposed COSMIC approximation approaches rely on an approximation of the size and/or numbers of the functional processes of the software to be measured. A consequence of the fact that the size of a single functional process has no finite limits is that multiple COSMIC approximation approaches have been developed. Therefore this document describes a number of approximation approaches with their pros and cons, their recommended area of application and their validity, rather than document, say, one particular COSMIC approximation approach.
The approaches described are:

  • The average functional process approximation
  • The fixed size classification approximation
  • The equal size bands approximation
  • Average use case approximation
  • Early & Quick COSMIC approximation
  • EASY function point approximation
  • Approximation from informally written textual requirements
  • Approximation using fuzzy logic – the EPCU model

Also a number of generic issues involved in Early or Rapid functional size measurement are discussed:

  • Different levels of granularity and decomposition
  • Localization principles
  • Approximate sizing of changes to functionality
  • Approximate sizing and scope creep

Rotterdam 2014