Project Estimation: Use Case Point Technique
Summary
estimates give an indicator of how long and how much effort is required to complete a project. There are many estimation methods available based upon expert opinion (e.g Wideband delphi), estimation by analogy - similar projects and also parameterised techiques (use case point).
This article presents a brief overview of the use case point estimation technique and includes an applet programme to allow you to perform a use case point based estimate for your current projects.
Detailed explanations of the Use Case Point analysis technique are available from a number of location - see references.
Liemur's Managing A RUP (MUP) Project course includes coverage and hands-on practice at using this technique.
Parameterised estimation techniques fall into one of two categories. They either calculate an estimate for the project based upon the project's volume (e.g. software lines of code - SLOC) or based upon the project's functionality (requirements). The problem with using estimation by volume is how do you know the number of lines of code to write before actually writing anything?
Estimation by use case point analysis uses the project's expected functionality in the form of the use case model to define the actual project size. Then by applying various factors to take account of the project environmental and technical aspects a value for amount of effort (in man hours) to complete the project is calculated. Having produced the effort estimate, a schedule estimate in calendar months can be derived. Beware, UCP estimates are exactly that, an estimate! -expect variance of +/-40%.
Use case point analysis was originally developed by Gustav Karner (1993) and later refined by Schneider and Winter (1998). It has been used on a number of projects, typcially during their initial stages, when only the functional (use case) model is available, to gain an understanding of the project size and to produce estimation for project schedule and effort.
The following steps are used for developing an estimate;
- Give a weighting value (0-5) for each project use case, use case actor, project environmental factors, technical factors
- Calculate the number of unadjusted use case points (UUCP) for the project
- Apply environmental and technical factors to obtain a value for the number of adjusted use case points in the project
- Apply factors for project team size to obtain the effort (man hours) to complete the project
To obtain actual schedule duration in months Boehm's COCOMO model can be used.
The following applet is an implementation of the use case point technique defined by Karner and includes refinements by Schneider and Winter. Duration is based upon Boehm's COCOMO calculation.
Download: We are glad to let you download a fully functional copy of this Java application.
References
http://isedj.org/isecon/2002/253d/Damodaran.Washington.pdf
http://www.bfpug.com.br/Artigos/UCP/Banerjee-UCP_An_Estimation_Approach.pdf
