Cocomo(gopi Gn)

[The Constructive Cost Model]

By G. Gopi Krishna Reddy

COCOMO OUTLINE INTRODUCTION THE BASIC MODEL Equations Limitations

INTERMEDIATE MODEL ADVANCE MODEL

COCOMO COCOMO is one of the most widely used

software estimation model in the world. It was developed by BARRY BOEHM in 1981 COCOMO predicts the effort and schedule for a

software product development based on inputs relating to the size of the software and a number of cost drivers that affect productivity

Types Of Forms COCOMO MODEL

Basic COCOMO

Intermediate COCOMO

Advanced COCOMO

COCOMO can be applied to three classes of software projects. a) organic mode - Relative small ,simple software projects. b) semi-detached mode - For intermediate software projects. c) Embedded mode - A software project that must be developed within set of hardware , software and operational constraints.

Basic COCOMO It is a static-valued model Computes software development effort as a function of

program size expressed in estimated lines of code. When to use: • Basic COCOMO is good for quick, early, rough order of magnitude estimates of software costs

Basic Model: Equations Mode

Effort

Organic

E=2.4*(KDSI)

1.05

TDEV=2.5*(E)

0.38

Semidetached E=3.0*(KDSI)

1.12

TDEV=2.5*(E)

0.35

Embedded

1.20

TDEV=2.5*(E)

0.32

E=3.6*(KDSI)

Schedule

Basic COCOMO Model: Limitations Its accuracy is necessarily limited because of

its lack of factors which have a significant influence on software costs The Basic COCOMO estimates are within a factor of 1.3 only 29% of the time, and within a factor of 2 only 60% of the time

Intermediate COCOMO Computes effort as function of program size and a lost

of cost drivers that include subjective assessment of product, hardware, personal and project attributes. When to use: The Intermediate Model can be applied across the entire software product for easily and rough cost estimation during the early stage or it can be applied at the software product component level for more accurate cost estimation in more detailed stages

Intermediate Model: Equations Mode Organic

Effort

Schedule 1.05

TDEV=2.5*(E)

1.12

TDEV=2.5*(E)

1.20

TDEV=2.5*(E)

E=EAF*3.2*(KDSI)

SemiE=EAF*3.0*(KDSI) detached Embedded E=EAF*2.8*(KDSI)

0.38

0.35

0.32

Intermediate Model: Limitations The Intermediate Model estimates are within

20% of the actuals 68% of the time Its effort multipliers are phase-insensitive It can be very tedious to use on a product with many components

Advanced COCOMO Incorporates all characteristics of the intermediate version with an

assessment of the cost driver’s impact on each step of the software engineering process. When to use : The Detailed Model can estimate the staffing, cost, and

duration of each of the development phases, subsystems, modules It allows you to experiment with different development strategies, to find the plan that best suits your needs and resources

Advanced Model: Equations Detailed Model uses the same equations for

estimations as the Intermediate Model Detailed Model uses a very complex procedure to calculate estimation. The procedure uses the DSIs for subsystems and modules, and module level and subsystem level effort multipliers as inputs

Advanced Model: Limitations Requires substantially more time and effort to

calculate estimates than previous models Detailed Model estimates are within 20% of the actuals 70% of the time

Conclusion It is well documented,available in the public domain and

supported by public domain and commercial tools. It has been widely used and evaluated in a range of organizations.