Information Systems

College of Business Administration
University of Missouri - St. Louis

Function Point Counting

  • A function point is a unit of measure.

  • Count Inputs, Outputs, Queries, Logical Files, Interface Files

  • Determine an adjustment factor based on system characteristics

  • Multiply the count by the adjustment.

  • Convert the count to hours.

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Notes:

    It is a work product expressed in terms of functionality as seen by the user.
    Count fields on windows, screens, reports.
    Count the types of data being tracked and interfaced.
    The adjustment factor takes things like performance, communication, technology, environment, and business rules into account.
    I like function point counts because it gives you a constant, derivable number that everyone understands and can discuss. It removes some of the politics and variability inherent in estimating.
    Convert the function point to hours based on the technology, tools, and experience.
    It has problems.
    On large systems it is time consuming.
    It does not do conversions and technology upgrades well (e.g., Y2K or install a new version of Oracle).
    Like any internal system documentation, it is difficult to maintain.
    Still better than nothing!!


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