the problems in software estimating
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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”. - PowerPoint PPT PresentationTRANSCRIPT
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Software Technology Support Center
The Problems in Software
Estimating
Dr. Randall JensenSoftware Technology Support Center
Hill AFB, UT
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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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Project Uncertainty Principle
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Software model genealogy
NordonIBM 1970
Putnam/SLIMUS Army/GE/QSM 1976
DotyRADC 1977
JS1,2,3CEI 1980
SEER-SEMGAI 1989
Seer II / SageSEI 1995
COCOMOTRW 1981
COCOMO IIUSC 1995
Validation
SeerHAC 1979
PRICE-SPrice 1977
TRUE-SPrice 2003
REVICUSAF 1991
Management
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Sage/SEER-SEM - Normal form
where K = life cycle cost (person years), Td = development time (years)
slocdtee TKCS
3dT
KD
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Common estimate dilemma
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Software problems are not new
Unreliable
Late delivery
Modification costs prohibitive
Impossible to maintain
Inadequate performance
Product exceeds budget costs
1968 CS Conference, Munich, Germany
KEY
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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
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Common technology claim
If you use (new technology),Productivity will improve by an order of magnitude
AndDefects will reduce to zero
Note: None of the history-based estimating models (tools) support this claim, not even close.
Neither does history.
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There is always HOPE
1960 1970 1980 1990
100
90
80
70
60
50
Ada
OOD
Structured Analysis
Structured DesignProcess Maturity
PWB
Structured Programming
3rd Generation Languages
PRODUCTIVITY
lppm
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3 Dimensions of development
PROJECT
PROCESSPEOPLE
1975
1985
1995
1938
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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?
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Where would you focus effort?
3
11
17
64
TOOLS
PEOPLE
SYSTEMS
MANAGEMENT
Source: G. Weinberg, Quality Software Management, Vol. 3
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Biased research?
Tools People Systems Managers0
10
20
30
40
50
60
70
SEI Papers
Pe
rce
nt
Source: G. Weinberg, Quality Software Management, Vol. 3
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Cost driver relative impact
Target ExperienceMultiple Sites
Develop Sys ExperienceMultiple Organizations
Resource LocationDevelopment Tools
Modern PracticesApplication Experience
Practices ExperienceStaff Capability
0 0.5 1 1.5 2 2.5
Relative Development Cost Impact
It takes people to implement processes and use technology.
April 21st, 2009
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BIG productivity drivers
Analyst capability Management style Motivation Use of team methods Working environment Problem solving skills
Programmer capabilityApplication domain experience Use of modern practicesAutomated tool support
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Capability shift (environment)
Basic Technology Constant
1980 2005
5500 750065006200 85008000
8635(1990)
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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?
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Problems?
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Popular estimating solution
Let’s create a new software model
Models are out of date
Models are inaccurate
Too difficult to use
Oh, really! Are you sure?
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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
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EstimatingPrediction is very hard, especially when it’s about the
future