Required development schedule

No change from COCOMO

The E coefficients represent the combined effects of multiple parameters. The post-architecture model uses parameters similar to those used by the conventional COCOMO model. These parameters allow the development environment to be characterized and normalized with the parameters in the COCOMO II project database (currently 83 projects). The effect of each parameter setting (very low, low, nominal, high, very high) is a multiplier that typically ranges from 0.5 to 1.5. The product of these 17 effects is used to compute the effort in the cost equation.

The name of the post-architecture model describes the product of the early design phase—namely, the architecture. The use of function points is recommended to quantify size for the early design phase, because function points are better suited to early phases when the structure (and hence the SLOC estimates) for the software solution is relatively unknown. The use of SLOC is recommended to quantify size for the post-architecture model. This approach seems to be a good technical compromise between the SLOC zealots and the function point zealots.

COCOMO II uses the same exponent for the early design and the post-architecture models. The process exponent can range from (1.01..1.26) and is defined as the combined effects of the following five parameters:

1. Application precedentedness: the degree of domain experience of the development organization

2. Process flexibility: the degree of contractual rigor, ceremony, and change freedom inherent in the project contract, life-cycle activities, and stakeholder communications

3. Architecture risk resolution: the degree of technical feasibility demonstrated before commitment to full-scale production

4. Team cohesion: the degree of cooperation and shared vision among stakeholders (buyers, developers, users, and maintainers, among others)

5. Process maturity: the maturity level of the development organization, as defined by the Software Engineering Institute's Capability Maturity Model

The COCOMO II exponent parameterization is an evolutionary upgrade of the Ada COCOMO approach with a more solid basis. Table B-7 summarizes the parameter ratings. The actual exponent for COCOMO II is determined by summing the effects for each parameter. The combined impact of these process parameters can be very high. The COCOMO II team has yet to permit an actual economy of scale to be achieved (that is, the value of P is never less than 1.0). They believe that economy of scale is achievable through corresponding reductions in size resulting from use of commercial components, reusable components, CASE tools, and object-oriented technologies.

Another interesting upgrade in COCOMO II is the schedule estimating equation, which is now a function of both the effort estimate and the process parameters. The resulting impact of a better process is a reduction in both effort and schedule.

Overall, COCOMO II is a good improvement over conventional cost models, many of which are grossly out of date. It is a good match for iterative development, modern technology, and the management process described in this book. However, it is also immature, and its project database still comprises diverse projects from numerous organizations. It is hard to believe that it will be any more reliable than the original COCOMO model.

Table B-7. COCOMO II process exponent parameters

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Project Management Made Easy

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