COCOMO

COCOMO is a set of hierarchical sub models which are basic, intermediate and detailed sub models. Basic model aims a quick rough estimate from small to medium sized project. Intermediate model adds more accuracy to the basic model by involving some attributes related to product, computer to be used, project personnel and project ,in the calculations. Finally the detailed model adds two extra capabilities namely phase sensitive effort multipliers and three level product hierarchy.

Project Types

Organic

Familiar environment, small team of experienced programmers are main characteristics of organic mode projects. For example, a personnel system project for an organization which is located on a single building with Local Area Network facilities only.

Semi Detached

Semi-detached mode projects are intermediate projects between organic mode and embedded mode. Such projects partially shows both characteristics. For example, a software project for a large bank, including daily customer operations and the ATM machine activities on a Wide Area Network can be considered as of type semi-detached..

Embedded

In the embedded mode, projects has tight constrains, more than one processor and various types of peripherals exist. Uncertainties in the problem definition is another characteristics of such projects. Hardware driving projects are good examples of embedded types. For example, a software project related to control the production of various automobile parts is of embedded type.

COCOMO Models

1. Basic Model

Basic model aims a quick rough estimate from small to medium sized project.

Effort Estimation:

Organic: K = 2.4 x S 1.05 Semi Detached: K = 3.0 x S 1.12 Embedded : K = 3.6 x S 1.20

Time Estimation:

Organic: t = 2.5 x K 0.38 Semi Detached: t = 2.5 x K 0.35 Embedded : t = 2.5 x K 0.32

2. Intermediate Model

Intermediate model adds more accuracy to the basic model by involving some attributes related to product, computer to be used, project personnel and project ,in the calculations.

Effort Estimation:

Organic: K = 3.2 x S 1.05 Semi Detached: K = 3.0 x S 1.12 Embedded : K = 2.8 x S 1.20

Time Estimation: Time formulas are the same as in Basic Model

Organic: t = 2.5 x K 0.38 Semi Detached: t = 2.5 x K 0.35 Embedded : t = 2.5 x K 0.32

Cost Drivers

In the table above, the abbreviations used are as follows:

RELY Required Software Reliability AEXP Application Experience DATA Data base size PCAP Programmers Capability CPLX Process Complexity VEXP Virtual machine Experience TIME Time Constraint for CPU LEXP Language Experience STOR Main Memory Constraint MODP Modern Programing Practices VIRT Machine Volatility TOOL Use of Software Tools TURN Turnaround time SCED Schedule Constraint ACAP Analysts Capability

Cost multiplier for normalisation is computed as choosing values from the table and multiplying them:

Where C : Cost Multiplier ci : Cost driver

Normalisation

The effort cost is normalised by cost multiplier and new effort is obtained:

Knew = K    x   C

This new effort value is used in time formulas to calculate estimated time cost.