Project Management

Question 1

What is

COCOMO?

Answer 1

The Constructive Cost Model

A procedural software cost estimation model developed by Barry W. Boehm.

It is used to model the expected cost of a development project based on program size and various “Cost Drivers”

Question 2

COCOMO:

Major Cost Drivers (4)

Answer 2

Product Attributes

Hardware Attributes

Personnel Attributes

Project Attributes

Question 3

COCOMO

Three Forms

Answer 3

Basic COCOMO

Good for quick, early, rough order of magnitude estimates, but has limited accuracy as it doesn’t account for cost drivers

Intermediate COCOMO

Expands on Basic COCOMO by incorporating cost drivers

Detailed COCOMO

Additionally accounts for the influence of individual product phases

Question 4

COCOMO:

The Effort Equation

Answer 4

E = a_{<span>i</span>}( KLoC )^(b_i) * EAF

• E is the effort applied, in “person-months”
• KLoC is the estimated number of thousands of delivered lines of code for the project
• Coefficients a_i and b_i are constants assigned depending on the nature of the software project
• EAF is the “Effort Adjustment Factor” based on the expected cost drivers

Question 5

COCOMO:

Cost Drivers:

How they are used

Answer 5

The Cost Drivers are used to calculate the Effort Adjustment Factor (EAF) for use in the effort equation.

• Each attribute is rated on a 6 point scale, from “very low” to “extra high” in importance or value
• A table defines multipliers that will be applied to each attribute, corresponding to it’s rating on the scale
• Finally, the multipliers from all ratings are multiplied together
• This results in an EAF, typically between 0.9 and 1.4

Question 6

COCOMO:

Important Equations

Answer 6

Effort Adjustment Factor (From Cost Drivers)

Effort Equation

Development Time

Number of Persons

Question 7

COCOMO

Development Time Equation

Answer 7

D = 2.5 E^(c_i)

• D is the development time in months
• E is the effort calculated by the effort formula
• c_i is a constant determined by the nature of the project

Question 8

COCOMO:

Persons needed Calculation

Answer 8

After calculating the Effort(E) and Development time(D),

the number of persons needed for a project is simply:

P = E/D

Question 9

COCOMO:

Software Project

Coefficients Table

Answer 9

Software project a_i b_i c_i Organic 3.2 1.05 0.38 Semi-detached 3.0 1.12 0.35 Embedded 2.8 1.20 0.32

Note: These are for Intermediate/Detailed COCOMO, Basic COCOMO has different coefficients for a_i, but b_i and c_i are the same