COCOMO MODEL

COCOMO (Constructive Cost Model) is a regression model based on LOC ie (Lines of Code)

It is cost estimate model for software projects & often used as process of reliably predicting various parameters associated with making a project such as size, effort, cost, time & quality .

The key parameters which define the quality of any software products, which are also an outcome of the cocomo are primarily Effort & Schedule:

Effort: Amount of Labor that will be required to complete a task. It is measured in person-months units.
Schedule: Amount of Time required for the completion of the job. It is measured in the units of time such as weeks and months

Boehm’s definition of organic, semidetached and embedded systems:

Organic: Small Team Size, Problem well understood and has been solved in the past
Semi-detached: Require more experience and better guidance and creativity. Ex. Compilers
Embedded: Require high level of complexity, creativity and experience. Larger team size

Types of COCOMO Models

Basic COCOMO Model
Intermediate COCOMO Model
Detailed COCOMO Model

Basic COCOMO Model

It is used for rough & quick calculations of software costs
Its accuracy is restricted due to absence of sufficient factor considerations.

Intermediate COCOMO Model

It focus on cost drivers (Reliability, experience, Capability)
It utilizes 15 drivers for cost estimation

Required software reliability extent
Size of the application database
The complexity of the product
Run-time performance constraints
Memory Constraints
The volatility of the virtual machine environment
Required turnaround time
Analyst capability
Software Engineering Capability
Application Experience
Virtual Machine experience
Programming language experience
Use of software tools
Application of software engineering methods
Required development schedule

Detailed COCOMO Model

It focus on individual project phases ie focus on cost drivers & calculations & produce final & accurate result. It utilizes 6 drivers for cost estimation

Planning and Requirements
System Design
Detailed design
Module code and test
Integration and Test
Cost Constructive Model

Estimation of Effort(Calculations)

Basic COCOMO Model

E = a(K LOC)^b Where E is Effort, K LOC is Kilo-Lines of Code
time = c(Effort)^d Where time is development time is measured in months
Person Required = Effort / Time

The constant values of a,b,c and d for the basic model for the different categories of system:

Software Projects	a	b	c	d
Organic	2.4	1.05	2.5	0.38
Semi Detached	3.0	1.12	2.5	0.35
Embedded	3.6	1.20	2.5	0.32

Example Suppose a project was estimated to be 400 KLOC. Calculate the effort & development time for each of the three model ie. organic, semi-detached & embedded

Solution:

The basic COCOMO equation takes form

Effort = a * (KLOC) ^b pm

Time_dev = c * (Effort) ^d months

Estimated Size of Project = 400 KLOC

(i) Organic Model

E = 2.4 * (400)^1.05
= 1295.31 pm
D = 2.5 * (1295.31)^0.38
= 38.07 pm

(ii) Semidetached Model

E = 3.0 * (400) ^1.12
= 2462.79 pm
D = 2.5 * (2462.79) ^0.35
= 38.45 pm

(iii) Embedded Model

E = 3.6 * (400) ^1.20
= 4772.81 pm
D = 2.5 * (4772.8) ^0.32
= 38 pm

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