CISSP Study Guide: Cost Estimation Models

Cost estimation models don’t entail developmental processes but are used to estimate costs of software development projects. An early example is the Basic COCOMO Model, which estimates software development effort and cost as a function of the size of the software product in source instructions. This model uses two equations:

1. The number of man-months (MM) required to develop the most common type of software product, in terms of the number of thousands of delivered source instructions (KDSI) in the software product. (MM = 2.4 (KDSI)05)
2. The development schedule (TDEV) in months. (TDEV = 2.5(MM)38)

A more advanced model, the Intermediate COCOMO Model, factors in hardware limitations, personnel quality, use of advanced tools, and other attributes and their aggregate impact on overall project costs.

An even more advanced model is the Detailed COCOMO Model, which factors in the effects of the additional factors used in the intermediate model on the costs of individual project phases.

The Function Point Measurement Model, another cost estimation model, does not require the user to estimate the number of delivered source instructions. Instead, it focuses on functions, including external input types, external output types, logical internal file types, external interface file types, and external inquiry types. These functions are calculated and evaluated according to complexity and used to determine software development processes.

A third type of model applies the Rayleigh curve to software development cost and effort estimation. Software Life Cycle Model (SLIM) uses this approach. SLIM makes its estimates by concentrating on the number of lines of source code that are modified by the manpower buildup index (MBI), which estimates the rate of buildup of staff on the project; and a productivity factor (PF), which is based on the technology used.