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

1. Basic COCOMO Model
2. Intermediate COCOMO Model
3. 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

1. Required software reliability extent
2. Size of the application database
3. The complexity of the product
4. Run-time performance constraints
5. Memory Constraints
6. The volatility of the virtual machine environment
7. Required turnaround time
8. Analyst capability
9. Software Engineering Capability
10. Application Experience
11. Virtual Machine experience
12. Programming language experience
13. Use of software tools
14. Application of software engineering methods
15. 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

1. Planning and Requirements
2. System Design
3. Detailed design
4. Module code and test
5. Integration and Test
6. Cost Constructive Model

Estimation of Effort(Calculations)

1. 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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