Introduction to the COSYSMO Model
The most fundamental calculation in the COSYSMO model is the use of the
Effort Equation to estimate the number of Person-Hours required to
develop a project. Most of the other COSYSMO results, including the
estimates for cost, effort per phase, and effort per activity, are
derived from this quantity.
To use COSYSMO to your best advantage, you should understand the
assumptions and definitions behind the model. The Constructive
Systems Engineering Model (COSYSMO)
describes the model in detail,
and indicates how the model was developed and validated. The
dissertation is installed in the SystemStar folder on the Start |
Programs menu with the name "The COSYSMO Model".
The COSYSMO calculations are based on your estimate of a project's size,
measured in terms of four size drivers:
The overall size for your project is derived from the counts you supply
for each size driver (e.g. 50 requirements, 5 interfaces, 2 algorithms,
3 scenarios). The overall size is expressed in terms of equivalent
requirements and is the fundamental input to the COSYSMO Effort
COSYSMO has 14 cost drivers - you assess your project, development
environment, and team to set each cost driver. The cost drivers are
multiplicative factors that determine the effort required to complete
the systems engineering portion of your project. For example, if your
team is the best you've ever worked with, you might set the
Personnel/Team Capability Cost Driver (PCAP) cost driver to Very High.
That rating corresponds to an effort multiplier of 0.66, meaning that
your project will require only 66% of the systems engineering effort
that a typical project would require.
COSYSMO Effort Equation
The COSYSMO model makes its estimates of required effort (measured in
Person-Hours - PH) based primarily on your estimate of the project's
size (as measured in equivalent requirements):
Effort = 38.55 * EAF * (Size) ** 1.06
38.55 Is a calibration constant
EAF Is the Effort Adjustment Factor derived from the Cost Drivers
Size Is calculated from the Size Drivers
1.06 Is a calibration constant
As an example, a project with all Nominal Cost Drivers would have an EAF
of 1.00. Assuming that the project is projected to consist of 100
equivalent requirements, COSYSMO estimates that 5,082 Person-Hours of
effort is required to complete it:
Effort = 38.55 * (1.0) * (100) ** 1.06 = 5,082 Person-Hours
Each SystemStar model implements a different set of Cost Drivers and
Effort Adjustment Factor
The Effort Adjustment Factor in the effort equation is simply the
product of the effort multipliers corresponding to each of the cost
drivers for your project.
For example, if your project is rated Very High for PCAP (effort
multiplier of 0.66), and Very High for Tool Support (effort multiplier
of 0.73), and all of the other cost drivers are rated to be Nominal
(effort multiplier of 1.00), the EAF is the product of 0.66 and 0.73.
Effort Adjustment Factor = EAF = 0.66 * 0.73 = 0.48
Effort = 38.55 * (0.48) * (100) ** 1.06 = 2,448 Person-Hours
The Effort Equation presented
above is the latest COSYSMO
equation - it's a generic equation based on data from a group of
aerospace corporations. Early experience indicates that this 'average'
equation doesn't estimate very well for any specific organization. It's
vital that you perform a 'local calibration' to determine the optimum
Effort Equation for your company.
"Calico for SystemStar", shipped with SystemStar, is the tool that
calibrates the COSYSMO equation to your historical data.