1. Software Engineering

2. Outline of this presentation
Constructive Cost Modeling (Constructive Cost Model)
3 COCOMO Models
Project Characteristics
Some Assumptions
Basic COCOMO Model
Equations
When Should You Use It
Limitations
Examples

3. Constructive Cost Modeling
COCOMO is one of the most widely used software estimation models in the world
It was developed by Barry Boehm in 1981
COCOMO predicts the effort and schedule for a software product development based on inputs relating to the size of the software and a number of cost drivers that affect productivity

4. Constructive Cost Modeling
3 COCOMO Models :
COCOMO has three different models that reflect the complexity:
the Basic Model
the Intermediate Model
and the Detailed Model

5. Constructive Cost Modeling
Project Characteristics
Organic Mode
Small to medium size product development
developed in a familiar, in-house & stable environment,
similar to the previously developed projects
relatively small and requires little innovation

6. Constructive Cost Modeling
Project Characteristics
Semidetached Mode
Team members have an intermediate level of experience with related systems.
Perhaps a mixture of experienced and inexperienced people.
Parts of the project may require rigorous interfaces.

7. Constructive Cost Modeling
Project Characteristics
Embedded Mode
tight, inflexible constraints and interface requirements
The product requires great innovation
Product must operate within a strongly coupled complex of H/W, S/W, regulations, and operational procedures.
Tighter requirements and more inflexible scheduling

8. Constructive Cost Modeling
Some Assumptions
Primary cost driver is the number of Delivered Source Instructions (DSI) developed by the project (LOC/KLOC)
COCOMO estimates assume that the project will enjoy good management by both the developer and the customer
Assumes the requirements specification is not substantially changed after the plans and requirements phase

9. Constructive Cost Modeling
Basic COCOMO Model
Basic COCOMO model estimates the software development effort using only a single predictor variable (size in DSI) and three software development modes

10. Constructive Cost Modeling
Basic COCOMO Model: Equations
Mode
Effort
Schedule
Organic
E=2.4*(KDSI)
1.05
TDEV=2.5*(E)
0.38
Semidetached
E=3.0*(KDSI)
1.12
0.35
Embedded
E=3.6*(KDSI)
1.20
0.32
Man-Month / Person-Month
Month
Effort in man-months
A COCOMO man-month consists of 152 hours of working time
KDSI is the Thousand Delivered Source Instructions
TDEV is the number of months estimated for software development

11. Constructive Cost Modeling
When Should You Use It
Basic COCOMO is good for quick, early, rough order of magnitude estimates of software costs

12. Constructive Cost Modeling
Limitation of Basic COCOMO Model
Its accuracy is necessarily limited because of its lack of factors which have a significant influence on software costs
The Basic COCOMO estimates are within a factor of 1.3 only 29% of the time, and within a factor of 2 only 60% of the time

13. Constructive Cost Modeling
An Example
We have determined our project fits the characteristics of Semi-Detached mode
We estimate our project will have 32,000 Delivered Source Instructions. Using the formulas, we can estimate:
FSP = Full-time equivalent Software Personnel, a measure of the equivalent number of people working on the project at a given time.

14. Constructive Cost Modeling
An Example
Effort = 3.0*(32) = 146 Man-Months
Schedule = 2.5*(146) = 14 Months
Productivity / Man Month = 32,000 DSI / 146 MM = 219 DSI/MM
Average Staffing / Month = 146 MM /14 M = 10 Man
FSP = Full-time equivalent Software Personnel, a measure of the equivalent number of people working on the project at a given time.

15. Constructive Cost Modeling
An Example
Bila sebuah proyek dikelompokkan kedalam organic mode project diperkirakan akan menghasilkan 32,000 DSI,
maka:
PM = 2.4 * (32) 1.05
= 91 p.m.
Dari nilai PM yang diperoleh dapat dihitung berapa lama proyek akan diselesaikan
TDEV = 2.5 (91) 0.38
= 14 bulan
FSP = Full-time equivalent Software Personnel, a measure of the equivalent number of people working on the project at a given time.

16. Constructive Cost Modeling
An Example
Bila sebuah proyek dikelompokkan kedalam embedded mode project diperkirakan akan menghasilkan 128,000 DSI, maka:
PM = 3.6 (128) 1.20
= p.m.
Dari nilai PM yang diperoleh dapat dihitung berapa lama proyek akan diselesaikan
TDEV = 2.5 (1216) 0.32
= 24 bulan
FSP = Full-time equivalent Software Personnel, a measure of the equivalent number of people working on the project at a given time.

17. Any
Questions?

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