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CHAPTER 5 SOFTWARE PROJECT PLANNING 133

ment component that enables E to be adjusted by other project characteristics (e.g.,
problem complexity, staff experience, development environment). Among the many
LOC-oriented estimation models proposed in the literature are

E = 5.2 x (KLOC) 0.91 Walston-Felix model
E = 5.5 + 0.73 x (KLOC) 1.16 Bailey-Basili model
E = 3.2 x (KLOC) 1.05 Boehm simple model
E = 5.288 x (KLOC) 1.047 Doty model for KLOC > 9
None of these models
should be used without FP-oriented models have also been proposed. These include
careful calibration to
your environment. E = 13.39 + 0.0545 FP Albrecht and Gaffney model
E = 60.62 x 7.728 x 10 -8 FP 3 Kemerer model
E = 585.7 + 15.12 FP Matson, Barnett, and Mellichamp model
A quick examination of these models indicates that each will yield a different result 14
for the same values of LOC or FP. The implication is clear. Estimation models must
be calibrated for local needs!

5.7.2 The COCOMO Model
In his classic book on “software engineering economics,” Barry Boehm [BOE81] intro-
duced a hierarchy of software estimation models bearing the name COCOMO, for
COnstructive COst MOdel. The original COCOMO model became one of the most widely
used and discussed software cost estimation models in the industry. It has evolved
into a more comprehensive estimation model, called COCOMO II [BOE96, BOE00].
Like its predecessor, COCOMO II is actually a hierarchy of estimation models that
address the following areas:
Application composition model. Used during the early stages of software
WebRef engineering, when prototyping of user interfaces, consideration of software
Detailed information on and system interaction, assessment of performance, and evaluation of tech-
COCOMO II, including nology maturity are paramount.
downloadable software,
can be obtained at Early design stage model. Used once requirements have been stabilized
sunset.usc.edu/ and basic software architecture has been established.
COCOMOII/ Post-architecture-stage model. Used during the construction of the
cocomo.html
software.
Like all estimation models for software, the COCOMO II models require sizing infor-
mation. Three different sizing options are available as part of the model hierarchy:
object points, function points, and lines of source code.
The COCOMO II application composition model uses object points and is
illustrated in the following paragraphs. It should be noted that other, more

14 Part of the reason is that these models are often derived from relatively small populations of proj-
ects in only a few application domains.