Page 107 - DCAP305_PRINCIPLES_OF_SOFTWARE_ENGINEERING

Unit 5: Software Project Planning

Man Month correction is now: Notes

MM = EAF*MM nominal
korr
Only the Intermediate form has been implemented by USC in a calibrated
software tool.
5.3.2 Advanced, Detailed COCOMO

The Advanced COCOMO model computes attempt as a purpose of program size and a set of
cost drivers weighted according to each phase of the software lifecycle. The Advanced model
applies the in-between model at the component level, and then a phase-based approach is used
to combine the estimate.
The four phases used in the detailed COCOMO model are: requirements planning and product
design (RPD), detailed design (DD), code and unit test (CUT), and integration and test (IT). Each
cost driver is broken down by phases as in the example shown in Table 5.2.

Table 5.2: Analyst Capability Effort Multiplier for Detailed COCOMO

Cost Driver Rating RPD DD CUT IT
ACAP Very Low 1.80 1.35 1.35 1.50
Low 0.85 0.85 0.85 1.20
Nominal 1.00 1.00 1.00 1.00
High 0.75 0.90 0.90 0.85
Very High 0.55 0.75 0.75 0.70

Estimates for each module are combined into subsystems and eventually an overall project
estimate. Using the detailed cost drivers, an estimate is determined for each phase of the lifecycle.
The COCOMO has been continued to evolve and improve since its introduction. Beneath the
“ADA COCOMO” model:
The model named “ADA_87” assumes that the ADA programming language is being used. The
use of ADA made it easier to develop highly reliable systems and to manage complex applications.
The APM_88 model is based upon a different “process model” called the ADA Process Model.
Among the assumptions are:
• ADA is used to produce compiler checked package specifications by the Product Design
Review (PDR).
• Small design teams are used.
• More effort is spent in requirements analysis and design.
• Less effort is spent in coding, integration, and testing.

The APM_88 model incorporates changes to the equations, several cost drivers, and a variety
of other tables.

Advantages of COCOMO’81
• COCOMO is transparent; one can see how it works unlike other models such as SLIM.
• Drivers are particularly helpful to the estimator to understand the impact of different
factors that affect project costs.
Drawbacks of COCOMO’81
• It is hard to accurately estimate KDSI early on in the project, when most effort estimates
are required.

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