An Analysis of Trends in Productivity and Cost Drivers over Years

The Constructive Cost Model (COCOMO) was originally
published in the text Software Engineering Economics [1]. This
original model is often referred to as COCOMO 81. The model
was defined based on the analysis of 63 completed projects from
different domains during the 1970s and the early 1980s. To
address the issues emerging from advancements and changes in
technologies and development processes, the USC Center for
Systems and Software Engineering has developed and published
COCOMO II. The model was initially released in [5] and then
published in the definitive book [2]. Among the main upgrades
are the introduction of new functional forms that use scale factors,
new cost drivers, and a new set of parameters’ values.
COCOMO II comprises of three sub-models, Applications
Composition, Early Design and Post-Architecture. The
Applications Composition model is used to compute the effort
and schedule to develop the system that is integrated from
reusable components and other reusable assets using integrated
development tools for design, construction, integration, and test.

The Applications Composition model has a different estimation
form from the other models. It uses Application Points or Object
Points [11][12] as the size input and a productivity rate to
calculate effort. The Early Design model is used in early stages of
the project when the project information is not detailed enough
for a fine-gain estimate. When the detailed information is
available (e.g., the high level design is complete, development
environment is determined), the Post-Architecture model is used
instead. The Early Design and Post-Architecture models use
source lines of code as the basic size input and follow the same
arithmetic form.