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The Problems in Software Estimating

The Problems in Software Estimating. Dr. Randall Jensen Software Technology Support Center Hill AFB, UT. Outline. Evolution of software estimating models Software problems Management is the issue Data collection concerns New models?. It’s all about models – “Existence is elsewhere”.

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The Problems in Software Estimating

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  1. The Problems in Software Estimating Dr. Randall Jensen Software Technology Support Center Hill AFB, UT BE AMERICA’S BEST

  2. Outline • Evolution of software estimating models • Software problems • Management is the issue • Data collection concerns • New models? It’s all about models – “Existence is elsewhere” BE AMERICA’S BEST

  3. Project Uncertainty Principle BE AMERICA’S BEST

  4. Software model genealogy Putnam/SLIM Nordon US Army/GE/ IBM 1970 Seer II / Sage SEI 1995 QSM 1976 Management Seer SEER-SEM JS1,2,3 HAC 1979 GAI 1989 CEI 1980 Doty Validation RADC 1977 COCOMO COCOMO II TRW 1981 USC 1995 REVIC USAF 1991 PRICE-S TRUE-S Price 1977 Price 2003

  5. Sage/SEER-SEM - Normal form sloc whereK= life cycle cost (person years), Td= development time (years) BE AMERICA’S BEST

  6. Common estimate dilemma BE AMERICA’S BEST

  7. Software problems are not new • Unreliable • Late delivery • Modification costs prohibitive • Impossible to maintain • Inadequate performance • Product exceeds budget costs KEY 1968CS Conference, Munich, Germany BE AMERICA’S BEST

  8. Historic note: “More software projects have gone awry for lack of calendar time than for all other causes combined…” F. P. Brooks, Jr., Mythical Man Month BE AMERICA’S BEST

  9. Common technology claim If you use (new technology), Productivity will improve by an order of magnitude And Defects will reduce to zero Note: None of the history-based estimating models (tools) support this claim, not even close. Neither does history. BE AMERICA’S BEST

  10. P R O D U C T I V I T Y lppm 100 90 80 70 60 50 Structured Analysis Ada Structured Design Process Maturity OOD PWB Structured Programming 3rd Generation Languages 1960 1970 1980 1990 There is always HOPE BE AMERICA’S BEST

  11. 3 Dimensions of development 1938 1975 1985 1995 BE AMERICA’S BEST

  12. Impact of management on cost “Poor management can increase software costs more rapidly than any other factor… Despite this variation, COCOMO does not include a factor for management quality, but instead provides estimates which assume that the project will be well managed[italics mine, RWJ]” Boehm, B. W., Software Engineering Economics, (Englewood Cliffs, NJ: Prentice-Hall, Inc.), 1981, pg. 486 Note: On a scale of 0 to 10 well managed must rank approximately 3.4? BE AMERICA’S BEST

  13. Where would you focus effort? TOOLS 3 PEOPLE 11 SYSTEMS 17 MANAGEMENT 64 Source: G. Weinberg, Quality Software Management, Vol. 3 BE AMERICA’S BEST

  14. Biased research? 70 60 SEI Papers 50 40 Percent 30 20 10 0 Source: G. Weinberg, Quality Software Management, Vol. 3 Tools People Systems Managers BE AMERICA’S BEST

  15. Cost driver relative impact It takes people to implement processes and use technology.

  16. BIG productivity drivers • Analyst capability • Management style • Motivation • Use of team methods • Working environment • Problem solving skills • Programmer capability • Application domain experience • Use of modern practices • Automated tool support BE AMERICA’S BEST

  17. Capability shift (environment) 1980 2005 8635 (1990) 5500 6200 6500 7500 8000 8500 Basic Technology Constant BE AMERICA’S BEST

  18. Historic data observations • Models are made from historic data • More data is better • Adequate historic data takes time to collect (Lots of time) • Repository vs Database • Repository = a place where things may be stored for safekeeping • Data stored without concern for a formal definition of the data placed in the repository • SRDR is defined as a financial report that happens to contain technical information • Database = a collection of data arranged for ease and speed of retrieval • Requires consistency of entries • Each data field must satisfy common definition • DCARC is a repository as was SMC database • Data definitions? BE AMERICA’S BEST

  19. Problems? BE AMERICA’S BEST

  20. Popular estimating solution Oh, really! Are you sure? • Let’s create a new software model • Models are out of date • Models are inaccurate • Too difficult to use BE AMERICA’S BEST

  21. New estimating models? • Lack of confidence in existing tools (current issues) • Optimistic estimates • Unacceptable estimates • Aging tools (?) • Culture is constant • New models require validation • New models -- No silver bullets • Quality data (if, where, proprietary) • New models require validation • New (or better) estimators? • Experience • Skill • Integrity BE AMERICA’S BEST

  22. Estimating Prediction is very hard, especially when it’s about the future

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