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CHAPTER 4 SOFTWARE PROCESS AND PROJECT METRICS 91

The F (i = 1 to 14) are "complexity adjustment values" based on responses to the
i
following questions [ART85]:
1. Does the system require reliable backup and recovery?
2. Are data communications required?
3. Are there distributed processing functions?
4. Is performance critical?
5. Will the system run in an existing, heavily utilized operational environment?
6. Does the system require on-line data entry?
7. Does the on-line data entry require the input transaction to be built over multiple
screens or operations?
8. Are the master files updated on-line?
9. Are the inputs, outputs, files, or inquiries complex?
10. Is the internal processing complex?
11. Is the code designed to be reusable?
12. Are conversion and installation included in the design?
13. Is the system designed for multiple installations in different organizations?
14. Is the application designed to facilitate change and ease of use by the user?
Each of these questions is answered using a scale that ranges from 0 (not important
or applicable) to 5 (absolutely essential). The constant values in Equation (4-1) and
the weighting factors that are applied to information domain counts are determined
empirically.
Once function points have been calculated, they are used in a manner analogous
to LOC as a way to normalize measures for software productivity, quality, and other
attributes:
• Errors per FP.
• Defects per FP.
• $ per FP.
• Pages of documentation per FP.
• FP per person-month.

4.3.3 Extended Function Point Metrics
The function point measure was originally designed to be applied to business infor-
Extending function mation systems applications. To accommodate these applications, the data dimen-
points are used for sion (the information domain values discussed previously) was emphasized to the
engineering, real-time, exclusion of the functional and behavioral (control) dimensions. For this reason, the
and control-oriented
applications. function point measure was inadequate for many engineering and embedded sys-
tems (which emphasize function and control). A number of extensions to the basic
function point measure have been proposed to remedy this situation.
A function point extension called feature points [JON91], is a superset of the function
point measure that can be applied to systems and engineering software applications.