Do a comparative study among the following COCOMO models:

(a) Basic

(b) Intermediate

(c) Complete

(d) COCOMO 2

The Constructive Cost Model (COCOMO) is an algorithmic software cost estimation model developed by Barry Boehm. The model uses a basic regression formula, with parameters that are derived from historical project data and current project characteristics.

COCOMO consists of a hierarchy of three increasingly detailed and accurate forms.

(a)BASIC COCOMO:  The first level, Basic COCOMO is good for quick, early, rough order of magnitude estimates of software costs, but its accuracy is limited due to its lack of factors to account for difference in project attributes (Cost Drivers). The Basic COCOMO model is a static, single-valued model that computes software development effort (and cost) as a function of program size expressed in estimated lines of code (LOC). The COCOMO models are defined for three classes of software projects. Using Boehm's terminology these are: (1) organic mode–relatively small, simple software projects in which small teams with good application experience work to a set of less than rigid requirements (e.g., a thermal analysis program developed for a heat transfer group); (2) semi-detached mode –an intermediate (in size and complexity) software project in which teams with mixed experience levels must meet a mix of rigid and less than rigid requirements (e.g., a transaction processing system with fixed requirements for terminal hardware and data base software); (3)embedded mode –a software project that must be developed within a set of tight hardware, software and operational constraints (e.g., flight control software for aircraft).

The Basic COCOMO equations take the form:

E = a_b KLOC ^b_b

D = c_b E ^d_b

where E is the effort applied in person-months, D is the development time in chronological months and KLOC is the estimated number of delivered lines of code for the project (express in thousands). The coefficients a_b and c_b and the exponents b_b and d_b are given below.

 Basic COCOMO Model

b) INTERMEDIATE COCOMO:  The Intermediate COCOMO model computes software development effort as a function of program size and a set of "cost drivers" that include subjective assessments of product, hardware, personnel and project attributes. This extension considers a set of four "cost drivers", each with a number of subsidiary attributes:-

• Product attributes

• • Required software reliability

• • Size of application database

• • Complexity of the product

• Hardware attributes

• • Run-time performance constraints

• • Memory constraints

• • Volatility of the virtual machine environment

• • Required turnabout time

• Personnel attributes

• • Analyst capability

• • Software engineering capability

• • Applications experience

• • Virtual machine experience

• • Programming language experience

• Project attributes

• • Use of software tools

• • Application of software engineering methods

• • Required development schedule

INTERMEDIATE COCOMO MODEL:

c) COMPLETE COCOMO:  A basic shortcoming of both basic and intermediate COCOMO models is that they consider software as a single homogeneous entity. However, most large systems are made up of several smaller subsystems. These subsystems often have widely different characteristics. The complete COCOMO model considers these differences in characteristics of the subsystems and estimates the eforrt and development time as the sum for the individual subsystems. In other words,the cost to develop each subsystem is estimated separately and the complete system cost is determined as the subsystem costs. This approach reduces the  margin of error in the final estimate.

d) COCOMO II: COCOMO II is tuned to modern software life cycles. The original COCOMO model has been very successful, but it doesn't apply to newer software development practices as well as it does to traditional practices. COCOMO II targets modern software projects, and will continue to evolve over the next few years.

COCOMO II is really three different models:

• The Application Composition Model

Suitable for projects built with modern GUI-builder tools. Based on new Object Points.

• The Early Design Model

We can use this model to get rough estimates of a project's cost and duration before we have determined its entire architecture. It uses a small set of new Cost Drivers, and new estimating equations based on Unadjusted Function Points or KSLOC.

• The Post-Architecture Model

This is the most detailed COCOMO II model. We will use it after we have  developed our project's overall architecture. It has new cost drivers, new line counting rules, and new equations.