Level 6: Size Approximation

There are various methods of approximating the functional size without counting all files and transactions. Such methods are often used for portfolio estimation, or as a basis for scheduling more detailed counts. They are based on characteristics of the application, which have been proven to have a strong correlation to size. E.g. numbers of reports, number of 3rd normal form tables, number of support staff etc. The size is estimated based on the answers to about 30 questions in a questionnaire.

Level 6 Size Approximation Description

A size Approximation includes the following:

• size estimate reported in unadjusted and / or adjusted function points
• assumptions documented in report

Level 6 Size Approximation Attributes

Size Approximation provides a result that:

• has very little detail –size results only
• accuracy historically has been demonstrated to be within (+/- 20%)
• is not documented other than the completed questionnaire and a very brief report on the result
• is not maintainable, they are snapshot of size only. They need to be redone if anything changes

Best suited for following count purposes:

• portfolio baseline assessment
• software asset valuation
• project scoping
• estimating count durations
• benchmarking support ratios
• most cost effective for large, legacy applications, which do not need their counts maintained

Issues:

• very efficient – most applications can have their size estimated within half a day
• very cost effective for large, legacy application baseline counts which have very little enhancement

Pre-requisites:

• accurate completion of a questionnaire (usually takes 2 hrs, but may take up to 2 days if the software is poorly documented or applications knowledge is limited)
• access to system experts (1 – 2 hour interview)