Software Project Planning The overall goal of project planning is to establish a pragmatic strategy for controlling, tracking, and monitoring a comple

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1 Estimation for Software Projects 1

2 Software Project Planning The overall goal of project planning is to establish a pragmatic strategy for controlling, tracking, and monitoring a complex technical project. Why? So the end result gets done on time, with quality! 2

3 Project Planning Task Set-I Establish project scope Determine feasibility Analyze risks Risk analysis Define required resources Determine required human resources Define reusable software resources Identify environmental resources 3

4 Project Planning Task Set-II Estimate cost and effort Decompose the problem Develop two or more estimates using size, function points, process tasks or use-cases Reconcile the estimates Develop a project schedule Scheduling Establish a meaningful task set Define a task network Use scheduling tools to develop a timeline chart Define schedule tracking mechanisms 4

5 Estimation Estimation of resources, cost, and schedule for a software engineering effort requires experience access to good historical information the courage to commit to quantitative predictions when qualitative information is all that exists Estimation carries inherent risk and this risk leads to uncertainty 5

6 Write it Down! Project Scope Estimates Risks Schedule Control strategy Software Project Plan 6

7 Resources number software tools skills hardware location people environment network resources project OTS components reusable software new components full-experience components part.-experience components 7

8 Project Estimation Project scope must be understood Elaboration (decomposition) is necessary Historical metrics are very helpful At least two different techniques should be used 8

9 Estimation Techniques 1. Past (similar) project experience 2. Conventional estimation techniques task breakdown and effort estimates size-oriented Metric Method Function-oriented oriented Metric Method 3. Empirical models 4. Automated tools 9

10 Size oriented Metric Method -Derived by considering the size of the software that has been produced. 10

11 Size oriented Metrics Errors per KLOC (Thousand lines of code). Defects per KLOC. $ per LOC. Page of documentation per KLOC. LOC per person-month One person-month is the amount of work done by one person in one month if they are working full time 11

12 CAD Software Example system (i)organizational average productivity for systems of this type= 620 LOC/pm. Estimated Effort = 33,200/ 620 = 54 person-months (ii) Cost per LOC = $ 13 Estimated Cost = X 13 = $431,000 12

13 Function oriented Metric Method - Based on functionality delivered by the application and complexity. Function Point FP = count total X [ Σ(Fi)] Where F i ( i=1 to 14) Complexity Adjustment Values 13

14 Complexity Adjustment Value Calculation 1. Does the system require reliable backup and recovery? 2. Are data communications required? 3. Are there distributed processing functions? 4. Is performance critical? 5. Will the system run in an existing, heavily utilized operational environment? 6. Does the system require on-line data entry? 7. Does the on-line data entry require the input transaction to be built over multiple screens or operations? 8. Are the master files updated on-line? 9. Are the inputs, outputs, files, or inquiries complex? 10. Is the internal processing complex? 11. Is the code designed to be reusable? 12. Are conversion and installation included in the design? 13. Is the system designed for multiple installations in different organizations? 14. Is the application designed to facilitate change and ease of use by the user? Values range from 0 to 5 14

15 Function oriented Metrics Errors per FP. Defects per FP. $ per FP. Pages of documentation per FP. FP per person-month. One person-month is the amount of work done by one person in one month if they are working full time 15

16 CAD Software Example system FP estimated = 375 (i) organizational average productivity for systems of this type = 6.5 FP/pm Estimated Effort = 375/6.5 = 58 person-months (ii) Cost per FP = $ 1230 Estimated Cost = 375 X 1230 = $ 461,000 16

17 Assignment 1. Compute the function point value for a project with the following information domain characteristics: Number of user inputs: 32 Number of user outputs: 60 Number of user inquiries: 24 Number of files: 8 Number of external interfaces: 2 Assume that all complexity adjustment values are average. 17

18 2. A software increment is delivered to end- users by a software team. The users uncover 8 defects during the first month of use. Prior to delivery, the software team found 242 errors during formal technical reviews and all testing tasks. What is the overall DRE for the project? 18

19 COCOMO-II COnstructive COst MOdel COCOMO II is actually a hierarchy of estimation models that address the following areas: Application composition model: Used during the early stages of software engineering, when prototyping of user interfaces, consideration of software and system interaction, assessment of performance, and evaluation of technology maturity are paramount. Early design stage model: Used once requirements have been stabilized and basic software architecture has been established. Post-architecture-stage model: Used during the construction of the software. 19

20 COCOMO II (Contd.) Object point - an indirect software measure that is computed using counts of the number of (1) screens (at the user interface), (2) reports, and (3) components likely to be required to build the application. 20

21 Object point Calculation Count X X X = = = Object point Count = 21

22 COCOMO Model II contd. New object point (Component based development or software reuse) NOP = (Object points) X [(100 - %reuse)/100] Estimated Effort = NOP / PROD 22

23 What is Empirical Model? Model based on information gained by means of observation, experience, or experiment rather than on mathematically describable relationships of the system. 23

24 Empirical Estimation Models General form: effort = tuning coefficient * size exponent usually derived as person-months of effort required either a constant or a number derived based on complexity of project usually LOC but may also be function point empirically derived One person-month is the amount of work done by one person in one month if they are working full time 24

25 Structure of Estimation model E = A + B X (e v ) C Where A, B and C are empirically derived constants E is effort in person-months is the estimation variable (either LOC or FP) e v Example: E = 5.2 X (KLOC) 0.91 E = X (KLOC) 1.16 E = FP E = FP 25

26 The Software Equation A dynamic multivariable model where E = [LOC x B /P] 3 x (1/t 4 ) E = effort in person-months or person-years t = project duration in months or years B = special skills factor P = productivity parameter 26

27 Delphi Method 1. The co-ordinator presents a specification and estimation form to each expert. 2. Co-ordinator calls a group meeting in which the experts discuss estimation issues with the coordinator and each other. 3. Experts fill out forms anonymously. 4. Co-ordinator prepares and distributes a summary of the estimates. 5. The Co-ordinator then calls a group meeting. In this meeting the experts mainly discuss the points where their estimates vary widely. 6. The experts again fill out forms anonymously. 7. Again co-ordinator edits and summarizes the forms, repeating steps 5 and 6 until the co-ordinator is satisfied with the overall prediction synthesized from experts. 27

28 The Make-Buy Decision simple (0.30) $380,000 system X build reuse buy major changes (0.60) difficult (0.70) minor changes (0.40) simple (0.20) complex (0.80) $450,000 $275,000 $310,000 $490,000 contract minor changes (0.70) $210,000 major changes (0.30) $400,000 without changes (0.60) $350,000 with changes (0.40) $500,000 28

29 Computing Expected Cost expected cost = (path probability) x (estimated path cost) i i For example, the expected cost to build is: expected cost = 0.30 ($380K) ($450K) similarly, build = $429 K expected cost reuse = $382K expected cost buy = $267K expected cost contract = $410K 29

30 Outsourcing SE activities are contracted to a third party who does the work at lower cost and higher quality. 30

31 Assignment 1. Use the COCOMO II model to estimate the effort required to build software for a simple ATM that produces 12 screens, 10 reports and will require approximately 80 software components. Assume average complexity and average developer/environment maturity. 2. Use the COCOMO II model to estimate the effort required to build software for a university examination system that produces 24 screens, 32 reports and will require approximately 10 software components. Assume average complexity and very low developer/environment maturity. 31

Estimation for Software Projects. Slides copyright 1996, 2001, 2005, 2009 by Roger S. Pressman. For non-profit educational use only

Chapter 26 Estimation for Software Projects Slide Set to accompany Software Engineering: A Practitioner s Approach, 7/e by Roger S. Pressman Slides copyright 1996, 2001, 2005, 2009 by Roger S. Pressman