The use case project estimation or 'Use Case Points' is a method for sizing and estimating projects developed with the object-oriented method, developed by Gustav Karner of Objectory (now Rational Software). The method is an extension of Function Point Analysis and Mk II Function Point Analysis (an adaption of FPA mainly used in the UK).
The Use Case Project Estimation report is intended to estimate the project size and duration of hourly manpower required based on the use case model. The report supports use case and SysML use case diagrams.
The use case point technique is applied to reestimate the project size. All the use cases used in the example below are based on the use case diagram. The following weight criteria are used:
Classifying Actors
The table below lists Actors Classifications
| Actor Complexity | Litmus Test to recognize classifications | Weight |
|---|---|---|
| Low Complexity | An external system with a well-defined API. | 1 |
| Average complexity | Either a human with a command line interface or an external system via some protocols or a database. | 2 |
| High complexity | A human with a GUI or a web page. | 3 |
Figure 1: Specification of Actor.
Unadjusted Actor Weights
Unadjusted Actor Weights (UAW) is obtained by counting how many actors there are in each category, multiplying each total by its weight, and adding up the products.
Determining Scenarios and Transactions of Use Cases
The table below lists Use Case Complexity
| Use Case Complexity | Litmus Test To Decide Classifications | Weight |
|---|---|---|
| Low complexity | 1 - 3 transactions | 5 |
| Average complexity | 4 - 7 transactions | 10 |
High complexity | > 7 transactions | 15 |
Figure 2: Use Case Driven - Use Case Complexity.
Unadjusted Use Case Weights
A transaction is a set of activities, which is either performed entirely or not at all. To determine the number of transactions, you need to count the use case steps. Next, multiply each use case type by the weighting factor and add up the products to get Unadjusted Use Case Weights (UUCW).
Unadjusted Use Case Point
Add UAW and UUCW to get Unadjusted Use Case Point (UUCP): UUCP = UAW + UUCW.
Reference Documents
- The Estimation of Effort Based on Use Cases, published by Rational software
ftp://ftp.software.ibm.com/software/rational/web/whitepapers/2003/finalTP171.pdf - COCOMO II
http://sunset.usc.edu/csse/research/COCOMOII/cocomo_main.html