COCOMO Model...

COCOMO (COnstructive COst MOdel) has been designed in 1981 by Barry Boehm to give an estimate of the number of man-months it will take to develop a software product and it is referred as COCOMO 81. COCOMO was first published in 1981 Barry W. Boehm's Book Software engineering economics as a model for estimating effort, cost, and schedule for software projects. It drew on a study of 63 projects at TRW Aerospace where Barry Boehm was Director of Software Research and Technology in 1981. The study examined projects ranging in size from 2,000 to 100,000 lines of code, and programming languages ranging from assembly to PL/I. These projects were based on the waterfall model of software development which was the prevalent software development process in 1981.

This is a simple on-line cost model for estimating the number of person-months required to develop software. The model also estimates the development schedule in months and produces an effort and schedule distribution by major phases.

Here is what Boehm says about the model in his Software Engineering Economics (1981) : "Basic COCOMO is good for rough order of magnitude estimates of software costs, but its accuracy is necessarily limited because of its lack of factors to account for differences in hardware constraints, personnel quality and experience, use of modern tools and techniques, and other project attributes known to have a significant influence on costs."

COCOMO, COnstructive COst MOdel is static single-variable model. There is a hierarchy of these models.

Model 1:

Basic COCOMO model is static single-valued model that computes software development  effort (and cost) as a function of program size expressed in estimated lines of code.

Model 2:

Intermediate COCOMO model computes software development effort as a function of program size and a set of "cost drivers" that include subjective assessments of product, hardware, personnel, and project attributes.

Model 3:

Advanced COCOMO model incorporates all characteristics of the intermediate version with an assessment of the cost driver's impact on each step, like analysis, design, etc.

The model estimates cost using one of three different development modes: organic, semidetached and embedded. Here is a summary of how Boehm describes the modes:

Organic

In the organic mode, relatively small software teams develop software in a highly familiar, in-house environment. Most people connected with the project have extensive experience in working with related systems within the organization, and have a thorough understanding of how the system under development will contribute to the organizations objectives. Very few organic-mode projects have developed products with more than 50 thousand delivered source instructions (KDSI).

Semidetached

The semidetached mode of software development represents an intermediate stage between the organic and embedded modes. "Intermediate" may mean either of two things:

1.    An intermediate level of project characteristic.

2.    A mixture of the organic and embedded mode characteristics.

The size range of a semidetached mode product generally extends up to 300 KDSI.

Embedded

The major distinguishing factor of an embedded-mode software project is a need to operate within tight constraints. The product must operate within (is embedded in) a strongly coupled complex of hardware, software, regulations, and operational procedures, such as an electronic funds transfer system or an air traffic control system.

It is very clear that the new automated system will work more efficiently and faster. So the users will certainly accept it. Also they are being actively involved in the development of the new system. Due to this fact they will know the system well and will be happy to use a new improved system.