The Constructive Cost Model (COCOMO) is a procedural
software cost estimation model developed by
Barry W. Boehm. The model parameters are derived from fitting a
regression formula using data from historical projects (63 projects for COCOMO 81 and 163 projects for COCOMO II).
History
The constructive cost model was developed by Barry W. Boehm in the late 1970s and published in Boehm's 1981 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 Boehm was Director of Software Research and Technology. The study examined projects ranging in size from 2,000 to 100,000
lines of code
Source lines of code (SLOC), also known as lines of code (LOC), is a software metric used to measure the size of a computer program by counting the number of lines in the text of the program's source code. SLOC is typically used to predict the am ...
, and programming languages ranging from
assembly
Assembly may refer to:
Organisations and meetings
* Deliberative assembly, a gathering of members who use parliamentary procedure for making decisions
* General assembly, an official meeting of the members of an organization or of their representa ...
to
PL/I
PL/I (Programming Language One, pronounced and sometimes written PL/1) is a procedural, imperative computer programming language developed and published by IBM. It is designed for scientific, engineering, business and system programming. I ...
. These projects were based on the
waterfall model
The waterfall model is a breakdown of project activities into linear sequential phases, meaning they are passed down onto each other, where each phase depends on the deliverables of the previous one and corresponds to a specialization of tasks. ...
of software development which was the prevalent software development process in 1981.
References to this model typically call it ''COCOMO 81''. In 1995 ''COCOMO II'' was developed and finally published in 2000 in the book ''Software Cost Estimation with COCOMO II''.
Barry Boehm
Barry William Boehm (May 16, 1935 – August 20, 2022) was an American software engineer, distinguished professor of computer science, industrial and systems engineering; the TRW Professor of Software Engineering; and founding director of the Cen ...
, Chris Abts, A. Winsor Brown, Sunita Chulani, Bradford K. Clark, Ellis Horowitz, Ray Madachy, Donald J. Reifer, and Bert Steece. '' Software Cost Estimation with COCOMO II'' (with CD-ROM). Englewood Cliffs, NJ:Prentice-Hall, 2000. COCOMO II is the successor of COCOMO 81 and is claimed to be better suited for estimating modern software development projects; providing support for more recent
software development process
In software engineering, a software development process is a process of dividing software development work into smaller, parallel, or sequential steps or sub-processes to improve design, product management. It is also known as a software devel ...
es and was tuned using a larger database of 161 projects. The need for the new model came as software development technology moved from mainframe and overnight batch processing to desktop development, code reusability, and the use of off-the-shelf software components.
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.
Last one is Complete COCOMO model which addresses the shortcomings of both basic & intermediate.
Intermediate COCOMOs
''Intermediate COCOMO'' computes software development effort as function of program size and a set of "cost drivers" that include subjective assessment of product, hardware, personnel and project attributes. This extension considers a set of four "cost drivers", each with a number of subsidiary attributes:-
* Product attributes
** Required software reliability extent
** Size of application database
** Complexity of the product
* Hardware attributes
** Run-time performance constraints
** Memory constraints
** Volatility of the virtual machine environment
** Required turnabout time
* Personnel attributes
** Analyst capability
** Software engineering capability
** Applications experience
** Virtual machine experience
** Programming language experience
* Project attributes
** Use of software tools
** Application of software engineering methods
** Required development schedule
Each of the 15 attributes receives a rating on a six-point scale that ranges from "very low" to "extra high" (in importance or value). An effort multiplier from the table below applies to the rating. The product of all effort multipliers results in an ''effort adjustment factor (EAF)''. Typical values for EAF range from 0.9 to 1.4.
The Intermediate Cocomo formula now takes the form:
:
where ''E'' is the effort applied in person-months, KLoC is the estimated number of thousands of delivered lines of code for the project, and EAF is the factor calculated above. The coefficient ''a
i'' and the exponent ''b
i'' are given in the next table.
:
The Development time ''D'' and also the most effective number of Persons ''P'' calculation uses ''E'' in the same way as in the Basic COCOMO:
:
:
Note that in addition to the EAF, the parameter ''a
i'' is different in ''Intermediate COCOMO'' from the Basic model:
:
The parameters ''b'' and ''c'' are the same in both models.
See also
*
Comparison of development estimation software In software development, effort estimation is the process of predicting the most realistic amount of effort (expressed in terms of person-hours or money) required to develop or maintain software based on incomplete, uncertain and noisy input. Effort ...
*
Cost overrun
A cost overrun, also known as a cost increase or budget overrun, involves unexpected incurred costs. When these costs are in excess of budgeted amounts due to a value engineering underestimation of the actual cost during budgeting, they are known ...
*
COSYSMO
*
Estimation in software engineering
Cost estimation in software engineering is typically concerned with the financial spend on the effort to develop and test the software, this can also include requirements review, maintenance, training, managing and buying extra equipment, servers ...
*
Function point
*
Object point Object points are an approach used in software development effort estimation under some models such as COCOMO II.
Object points are a way of estimating effort size, similar to Source Lines Of Code (SLOC) or Function Points. They are not necess ...
*
Putnam model The Putnam model is an empirical software effort estimation model.
The original paper by Lawrence H. Putnam published in 1978 is seen as pioneering work in the field of software process modelling.
As a group, empirical models work by collecting so ...
*
SEER-SEM
SEER for Software (SEER-SEM) is a project management application used to estimate resources required for software development.
History
1966 System Development Corporation Model based on regressions.
1980 Don Reifer and Dan Galorath paper whic ...
*
Software development effort estimation In software development, effort estimation is the process of predicting the most realistic amount of effort (expressed in terms of person-hours or money) required to develop or maintain software based on incomplete, uncertain and noisy input. Effort ...
*
Software engineering economics
Software engineering is a systematic engineering approach to software development.
A software engineer is a person who applies the principles of software engineering to design, develop, maintain, test, and evaluate computer software. The term ' ...
*
PRICE SystemsUnison Cost Engineering formerly known as PRICE Systems was founded in 1975 as a business within the RCA Corporation. It is generally acknowledged as the earliest developer of parametric cost estimation software.
PRICE Systems’ cost estimating s ...
References
Further reading
*
External links
COCOMO 81 dataon tera-PROMISE
Analysis of the COCOMO 81 dataobtains a different value for the Organic exponent.
{{DEFAULTSORT:Cocomo
Software engineering costs