What is the COCOMO model?

The COCOMO model#

COCOMO stands for the constructive cost model, a cost estimation model for software projects based on LOC.

The COCOMO model calculates a proposed software project's time, effort, cost, and quality. In simple words, it predicts the performance of a software project.

Types of software projects#

The COCOMO model can be applied to three types of software projects:

• Organic project: An organic software project requires a small team, the problem is well understood, and the team members are experienced in developing similar projects.

• Semi-detached project: A semi-attached project is medium-sized, with the development consisting of a mix of experienced and inexperienced staff, and the major characteristics of the project lie in between organic and embedded.

• Embedded project: An embedded software project has a high level of complexity, requiring a large-sized experienced team, and is coupled with complex hardware.

Types of COCOMO models#

The COCOMO model is divided into three types based on the accuracy quotient.Any of the three types can be adapted according to our requirements:

• Basic model

• Intermediate model

• Detailed model

Basic model#

The basic model is used for quick and rough cost calculations for the software. It calculates the effort, time, and number of people required to use a project's kLOC (kilo lines of code).

The formulae to calculate these entities are:

The effort is measured in person-months and time in months. The constants $a, b, c, and \space d$ vary for each model type. The following are the constant values for the basic model:

Example#

Suppose a project was estimated to be made in 400 kLOC. Lets calculate its effort, time, and the number of people required while considering the project is of organic type:

Calculate with Cocomo basic calculator#

Now, let's predict the performance of a software project with a cocomo basic calculator.

Intermediate model#

The intermediate model is an extension of the basic model and includes a set of cost drivers to calculate the estimates with better accuracy. The effort factor includes the effort adjustment factor (EAF) that is calculated with the cost drivers.

The formulae to calculate these entities are:

The effort is measured in person-months and time in months. The constants $a, b, c, and \space d$ vary for each model type. The following are the constant values for the basic model:

Cost drivers#

The cost drivers and their attributes are as follows:

Product attributes#

The product attributes are as follows:

• Required software reliability extent

• Size of the application database

• The complexity of the product

Hardware attributes#

The hardware attributes are as follows:Run time performance constraintsMemory constraintsThe volatility of the virtual machine environmentRequired turnabout time

Personal attributes#

The personal attributes are as follows:

• Analyst capabilities

• Software engineering capabilities

• Applications experience

• Virtual machine experience

• Programming language experience

Project attributes#

The project attributes are as follows:

• Use of software tools

• Application of software engineering methods

• Required development schedule

The EAF is calculated by multiplying the parameter values of different cost driver attributes. Ideally, the value is 1.

Example#

Suppose a project was estimated to be made in 400 kLOC.let's calculate its effort, time, and the number of people required while considering the project is of organic type and has a nominal complexity. The developer has a high virtual machine experience.

The value of the nominal complexity of a project is 1.00, and the high virtual experience of the developer is 0.90, according to the tables mentioned above:

Calculate with Cocomo intermediate calculator#

Now, let's predict the performance of a software project with cocomo intermediate calculator.

Detailed model#

The detailed model is a combination of both the basic model and the intermediate model. The model is decomposed into multiple modules, and the COCOMO model is applied to them individually. This model uses various effort multipliers for each cost driver attribute, and the cost is calculated at each stage separately.

The six stages of the detailed model are as follows:

• Planning and requirements

• System design

• Detailed design

• Module code and test

• Integration and test

• Cost constructive model

Conclusion#

The COCOMO model provides a good rough estimation of the cost of the project and the time taken to complete it. Still, it also has limitations as it ignores the factors like customer skills and knowledge. Moreover, in real life, things may not work out according to the model, and the project may take more time than the estimated time and affect the project.