Subject: Software Engineering

Topic: Matrics for Process & Projects

Difficulty: High

The Constructive Cost Model (COCOMO) is an algorithmic software cost estimation model developed by Barry Boehm. The model uses a basic regression formula, with parameters that are derived from historical project data and current project characteristics.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. These projects were based on the waterfall model of software development which was the prevalent software development process in 1981.

References to this model typically call it COCOMO 81. In 1997 COCOMO II was developed and finally published in 2000 in the book Software Cost Estimation with COCOMO II. COCOMO II is the successor of COCOMO 81 and is better suited for estimating modern software development projects. It provides more support for modern software development processes and an updated project database.

The need for the new model came as software development technology moved from mainframe and overnight batch processing to desktop development, code re-usability and the use of off-the-shelf software components. This article refers to COCOMO 81.COCOMO consists of a hierarchy of three increasingly detailed and accurate forms. The first level, Basic COCOMO is good for quick, early, rough order of magnitude estimates of software costs, but its accuracy is limited due to its lack of factors to account for difference in project attributes (Cost Drivers). Intermediate COCOMO takes these Cost Drivers into account and Detailed COCOMO additionally accounts for the influence of individual project phases.

The Constructive Cost Model (COCOMO) is an algorithmic software cost estimation model developed by Barry Boehm. The model uses a basic regression formula, with parameters that are derived from historical project data and current project characteristics.Program size is expressed in estimated thousands of lines of code (KLOC).COCOMO applies to three classes of software projects:

1.Organic projects - "small" teams with "good" experience working with "less than rigid" requirements

2.Semi-detached projects - "medium" teams with mixed experience working with a mix of rigid and less than rigid requirements

3.Embedded projects - developed within a set of "tight" constraints (hardware, software, operational, ...)The basic COCOMO equations take the form

Effort Applied = ab(KLOC)bb [ man-months ]

Development Time = cb(Effort Applied)db [months]

People required = Effort Applied / Development Time [count]