Software Sizing Experiences in the Classroom. Presented at the 18th International Forum on COCOMO and Software Cost Modeling

Transcription

1 Software Sizing Experiences in the Classroom Presented at the 18th International Forum on COCOMO and Software Cost Modeling Jo Ann Lane 21 October 2003

2 Academic Goals with Respect to Software Sizing Emphasize the importance of software sizing with respect to typical business goals Overview current techniques Encourage students to try one or more current techniques Challenge students to find a better approach COCOMO and Software Cost Modeling: 21 Oct 2003 JA Lane - 2

3 Teaching Approach Early in the course Overview various techniques and counting rules Provide guidelines for selecting an approach As part of team projects, students must Develop initial estimate Monitor estimates and update if necessary Perform final count to compare to estimates Identify probable causes for any significant estimation inaccuracies COCOMO and Software Cost Modeling: 21 Oct 2003 JA Lane - 3

4 Quantitative Comparison of Results Obtained to Date Team project characteristics Preferred sizing techniques Estimation accuracy Probable reasons for estimation inaccuracies COCOMO and Software Cost Modeling: 21 Oct 2003 JA Lane - 4

5 Team Project Characteristics Fixed schedule (1 semester/15 weeks) New Access database application that requires development of Database schema Screens Reports COCOMO and Software Cost Modeling: 21 Oct 2003 JA Lane - 5

6 Team Project Characteristics (continued) Students provided with performance and environment requirements as well as functional requirements Must be developed for the NT environment Team size: 5-6 people Data collected from 16 teams over 2 years COCOMO and Software Cost Modeling: 21 Oct 2003 JA Lane - 6

7 Student s Selected Sizing Methods for Development Activities* Number of Teams Using SLOC UFP AP Sizing Method * In addition, some testers have used use cases to estimate testing activities with some success COCOMO and Software Cost Modeling: 21 Oct 2003 JA Lane - 7

8 Software Sizing Accuracy Versus Phase 4X X Top Level Design 0.25X Concept of Operations Feasibility Detailed Design Accepted Software COCOMO and Software Cost Modeling: 21 Oct 2003 JA Lane - 8

9 Student Data Comparison with Industry Data Accuracy at Requirements Phase: All Sizing Methods Relative Size Accuracy Upper Limit Lower Limit Student Data COCOMO and Software Cost Modeling: 21 Oct 2003 JA Lane - 9

10 Student Data Comparison with Industry Data Accuracy at Requirements Phase: Application Points Relative Size Accuracy Upper Limit Lower Limit Student Data COCOMO and Software Cost Modeling: 21 Oct 2003 JA Lane - 10

11 Student Data Comparison with Industry Data Accuracy at Requirements Phase: Unadjusted Function Points (UFP) Relative Size Accuracy Upper Limit Lower Limit Student Data COCOMO and Software Cost Modeling: 21 Oct 2003 JA Lane - 11

12 Student Data Comparison With Industry Data Accuracy at Requirements Phase: SLOC Relative Size Accuracy Upper Limit Lower Limit Student Data COCOMO and Software Cost Modeling: 21 Oct 2003 JA Lane - 12

13 Student Reasons for Software Size Estimation Inaccuracies 17% 8% 4% 17% Misjudged Software 37% 17% Complexity Did Not Fully Understand Reqs Did Not Implement All Reqs General Lack of Experience Lack of Experience with Access Changed Implementation Lang COCOMO and Software Cost Modeling: 21 Oct 2003 JA Lane - 13

14 Feedback from Students It s HARD. especially trying to estimate using SLOC Complexity from the student s point of view is probably very different from what was intended in sizing rules in hindsight, students report that they probably overestimated complexity COCOMO and Software Cost Modeling: 21 Oct 2003 JA Lane - 14

15 Feedback from Prospective Employers Excited to hear that estimation processes are being taught Ask students if any new/better techniques are on the horizon (translation: hiring managers are still looking for a better way) COCOMO and Software Cost Modeling: 21 Oct 2003 JA Lane - 15

16 Instructor Assessment of Student Sizing Efforts To the casual observer, sizing inaccuracies for students using UFPs or APs is not much different than research data from industry Reasons that initial software sizes are off not much different from reasons found on real projects COCOMO and Software Cost Modeling: 21 Oct 2003 JA Lane - 16

17 Instructor Assessment of Student Sizing Efforts (continued) Correlation between functional requirements and software size is fairly stable Correlation between performance/environment requirements and software size is not as predictable Current complexity factors may not adequately address some performance issues COCOMO and Software Cost Modeling: 21 Oct 2003 JA Lane - 17

18 Instructor Assessment of Student Sizing Efforts (continued) Some of the hard or time-consuming requirements that did not get completed probably had little or no impact on student s software size estimates Web-enable application Set up security user groups to limit system access Provide help text for forms and fields COCOMO and Software Cost Modeling: 21 Oct 2003 JA Lane - 18

19 Instructor Assessment of Student Sizing Efforts (continued) UFP counts are probably extremely high due to lack of experience with logical file concepts however, actual counts use the same counting rules, so counting errors are probably not significant COCOMO and Software Cost Modeling: 21 Oct 2003 JA Lane - 19

20 Questions? COCOMO and Software Cost Modeling: 21 Oct 2003 JA Lane - 20