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CSE7315M14 Slide # 3 January 11, 2004 CSE SW Project Management / Module 14 - Size Estimating Notes and Reuse Copyright © , Dennis J. Frailey, All Rights Reserved Detailed Planning - Processes Estimate Schedule Evaluate Source Information Statement of Work Requirements Constraints Standards Processes History etc. WBSSize Effort & Cost ScheduleOK Complete Detailed Planning Revise & Negotiate Not OK Estimate Size Estimate Effort and Cost
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CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and ReuseCopyright © 1995-2004, Dennis J. Frailey, All Rights Reserved Slide 1
CSE7315M14
January 11, 2004
SMU CSE 7315 / NTU SE 584-NPlanning and Managing a
Software Project
Module 14Size Estimating Notes and
Reuse
Slide # 2 January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Objectives of This Module• To discuss some general points
about size estimating• To discuss how to deal with reuse
when estimating
Slide # 3 January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Detailed Planning - Processes
EstimateScheduleEvaluate
Source InformationStatement of Work
RequirementsConstraintsStandardsProcesses
Historyetc.
WBS Size
Effort &
Cost
Schedule
OKCompleteDetailedPlanning
Revise &Negotiate
Not OK
EstimateSize
EstimateEffort and
Cost
Slide # 4 January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
What Method if No Data?• What if you have absolutely no data
on the code to be written?– no prior experience– no expertise available
• You may be able to try something like function points if you know the functional requirements
• Or wideband Delphi• Or just count requirements
Slide # 5 January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Risk Management
The less you know when estimating, the more you need to plan on several updated estimates as you learn more
Slide # 6 January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
What About Non-Software WBS Tasks that do Not Influence Size?
• Some of these may depend on size– Number and size of documents
required– Management costs– Number of reports– Magnitude of support functions– Cost of inspections
• Such tasks will be estimated (for effort or cost) AFTER size is estimated (see later)
Slide # 7 January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
What about Non-software WBS Tasks that do Not Influence Size? (continued)
• Other tasks may be independent of size but dependent on effort or headcount– Number of workstations– Number of copies needed for
compilers, tools– etc.
Slide # 8 January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Other Non-Software WBS Tasks • Some tasks may be independent of
size or effort– Travel to attend reviews and
meetings with customer– Legal fees for setting up contracts– etc.
All of these non-software tasks will be addressed during effort and cost
estimating
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Final Notes1) Use more than one method and resolve
discrepancies– No method is reliable enough in most cases– When two methods disagree, it tells you you
are missing some facts
Method 1 WidebandDelphi
Resolution?
Method 3
Method 2Statistical Analysis
OK
(Revise Estimates)
Not OK
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Final Notes(continued)
2) Include data declarations in size estimates
3) Include all functions - many are easy to overlook or underestimate– Control– Power up– Power failure– Diagnostics– Operating Systems
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Final Notes(continued)
4) Select products (software items) carefully– Simplify interfaces – Minimize impact on support & maintenance– Fit the hardware in a reasonable fashion– Size should be manageable– One geographic area (preferably one
organization) for development– Allow incremental builds
Continued...
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Final Notes(continued)
4) Select products (software items) carefully– Consider design and documentation
requirements– Too many SIs results in management
overhead and potentially higher cost– Too few SIs increases risk (less
visibility; harder to test; harder to maintain)
Slide # 13 January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
5) Don’t under-scope what you don’t understand– built-in test requirements– control panels– displays– .....
Final Notes(continued)
The biggest estimating errors are errors of
ignorance
“I didn’t realize that this part of the software was so complex.”
Slide # 14 January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Final Notes(continued)
6) Consider the design methodology carefully– newer methods can be more
productive– but older ones often have less
risk due to experience, availability of tools, etc.
Slide # 15 January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Final Notes(continued)
7) Account properly for reuse– do it - reuse can save lots of
money– don’t consider it to be free
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Spreadsheet
CoCoMo BasedEffort Estimate
Other EffortEstimates ...
Size / Reuse Effort Effort & Cost Schedules
Final EffortEstimate
ProductivityBased Effort
Estimate
Generic Schedule
Effort Schedule
Labor Schedule
Cost Schedule
Analogy basedSize Estimate
SoftwareReuse
Analysis
Other SizeEstimates ...
Final SizeEstimate
Expert BasedSize Estimate
Slide # 17 January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Dealing with Reuse• Many software programs are
derived from previous programs• This MAY result in savings of cost
and/or time• It MAY also result in increased
qualityBUT
• Reuse can also cost more and take longer and yield lower quality
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Quality = x Reused:Quality = x
New:Quality = y
Old Software New Software
• Quality of new software depends on x and y.• If old software has poor quality it brings down
the quality of the new software.• But if it has high quality, it brings quality up.
Reuse Quality Diagram
Slide # 19 January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
What Can be Reused? ... ...Just About Anything
• Code• Test Code• Test Cases and Procedures• Documentation• Design Specifications• Designs
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Reuse is Almost Never “Free”• Because you seldom have everything
you need– You typically need to create tests or
documents or other things• And you need to design the software to
incorporate the “reused” components• And you need to integrate the “reused”
components with everything else
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Reuse TerminologyLegacy Code Code developed for a previous application &
BELIEVED TO BE OF USE for new applicationModified Code Code developed for a previous application
that is suitable for a new application after a MODEST AMOUNT OF MODIFICATION
Reused Code Code developed for previous application
suitable WITHOUT CHANGE OF ANY KIND
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Legacy Code vs. Reusable Code
Legacy Code• Designed for a
Specific Application• Lax Standards for
– Documentation– Test Procedures– Test Cases
Like looking in a junkyard to find something of use
Reusable Code• Designed for Several
Applications• Good Standards for
– Documentation– Test Procedures– Test Cases
Like looking in a library to find something of use
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Documenting Reuse Estimates
I tem NewLOC
ModifiedLOC
ReusedLOC
TotalLOC
Component #1 1233 0 0 1233Component #2 0 988 0 988Component #3 0 0 781 781Component #4 560 245 0 805Component #5 345 549 420 1314Total 2138 1782 1201 5121
• The total LOC column is total delivered lines of code
• This could be applied equally to function points or other measures
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
How Do You Count How Much of a Component is Modified or
Reused?• Consider Component #4 and
Component #5 on the previous slide• A Rule of Thumb:
– Go to the smallest level known• Unit or module (typically about 100 LOC)
– If the unit is not changed, it is “reused”– If the unit is changed, it is “modified”– If more than 50% of the unit is
changed, it is “new”
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Incorporating Several Distinct Kinds of Modified Code
I tem NewLOC
ModifiedType 1
ModifiedType 2
ReusedLOC
TotalLOC
Component #1 1233 0 0 0 1233Component #2 0 988 0 0 988Component #3 0 0 0 781 781Component #4 560 0 245 0 805Component #5 345 302 247 420 1314Total 2138 1290 492 1201 5121
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
TotalDelivered
SizeConversion
Process EquivalentSize
ReuseInformation
Calculating the Benefit of Reuse
• After estimating size, and before estimating effort, you must convert reused code to “equivalent” new code
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
How Do You Convert?• The conversion factor is based on
how much less effort you will expend for reused or modified code than for new code
• Assuming you have historical justification of the conversion factors, you can do a simple calculation
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Conversion Factor Example• Equivalent size can be estimated
directly via “reuse factors,” e.g.: – Reused code takes about 30% as much
effort as new code– Modified code takes 60% as much effort
as new code
I tem New Modified Reused TotalTotal 2,138 1,782 1,201 5,121Factor 100% 60% 30%Net 2,138 1,069 360 3,568
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Example Concluded• This says that the total effort to
develop these 5121 lines of code will be comparable to that of producing 3567 lines of new code.
• The same approach can be used for function points or other measures of software size.
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Where Did Those “Reuse Factors”
Come From?• Experience!– Over many hundreds of projects– But these are averages, and they vary a lot
• Your experience may vary from mine– You must keep track in order to know
• Different kinds of modified code may have different factors
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Typical Reuse FactorsEase of Using Reused
Modifi ed
Concurrent (*) .5-1% 1-3% Easy 10% 25% Average 30% 60% Hard 40% 75%
(*) See later slides for information on concurrent reuse
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
We Can Get More Accurate• If we are willing to look more closely
at the– Process &– Reuse Characteristics,
• Then we can gain a deeper understanding of the reuse impact
• We can also use this information to calculate the reuse factors used in the previous example
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
First Examine the Process• List the steps of the process• Then determine the % of the total
effort expended in each step, when developing new code
• Note that this is effort, not time• Example:
Requirements Design Code & Test I ntegration18% 25% 25% 32%
Slide # 34 January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Next Develop a Factor to Represent the Reuse Benefit
in Each Process StepRequire-ments
Design Code and Unit
Test
Integration
Relative Effort
18% 25% 25% 32%
Reuse Factor
10% 15% 5% 75%
Modified Factor
40% 35% 55% 80%
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
For Example …• Let RM be the % of the requirements
effort for this reused software– We must analyze requirements to see if
reused code can be used• Let DM be the % of the design effort for
this reused software– We may have to plan to test the software
and maybe design the rest of the software in a special way
Continued...
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
For Example (continued)
• Let CM be the % of the coding and unit testing effort required for this reused software– Normally 0 for “pure reused” code,
but not for modified code• Let IM be the % of the integration
effort required for this code – often 50-100% even for pure reused
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Applying the More Accurate Method
• For each phase of the process– Determine % Effort for – Determine the Effect of Reuse
Process StepReqs DesignCode I ntegrationPercent 18% 25% 25% 32%
Delivered Equivalent2,138 New 100% 100% 100% 100% 2,1381,782 Modified 20% 40% 70% 100% 1,1241,201Reused 10% 0% 0% 100% 4065,121 Total 3,668
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
• Once again, the method can be used for any measure of size, such as function points, feature points, etc.
• For truly reused code– CM is probably 0, but maybe you must do
some test code, so perhaps it is not – RM and DM are probably > 0
• It takes effort to analyze and determine whether reused code will work
– IM is generally not 0 • You have to run the integration tests ...
Notes
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Why is it “Modified” if You Change it Only a Little Bit
• Totally reused code has:– Identical documentation– Identical test procedures, code, etc.– One master copy to maintain in the
configuration management library– One part number for record keeping,
inventory, etc.Continued...
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Why is it “Modified” if you Change it Only a Little Bit
(continued)• Even if you change 1 comment line
– You need to maintain two copies in the CM library (of code, test code, etc.)
• And if you change 1 line of executable code– You need to change tests and
documentation
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
What About Concurrent Reuse?
• “Concurrent” reuse is reusing something multiple times within the same software product– For example, if the same subroutine is used
in each of several system components• It has very low cost, but it is not “free”
– You have to integrate and test each component
– And if you find a problem, you must fix it multiple times
Slide # 42 January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Reuse Factor To Use for Concurrent Reuse
• Typically, a concurrent reuse situation calls for a factor no larger than 5%– If the initial code is new or heavily
modified, the second and subsequent uses (concurrent reuse) tend to need factors of about 2-4%
– If the initial code is reused or lightly modified, the proper factor tends to run from 0.5% to 2%
Slide # 43 January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Concurrent Reuse ExampleItem New Modified Reuse
dConcurren
t ReuseTotal
Total 2,138
1,782 1,201 2,000 7,121
Factor 100%
60% 30% 1%
Net 2,138
1,069 360 20 3,588
Slide # 44 January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Maintenance vs Reuse?• If you have a large amount of code
and are modifying only a part of it, as in a maintenance situation, is this a form of reuse? If so, what reuse factor is appropriate?– Typically the factor would be very small– Often, people estimate maintenance
with a bottom-up technique rather than as a form of “reuse”
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
More Notes on Reuse• The earlier in the process you
reuse, the more leverage you get– Reusing an architecture or a design
will support multiple target machines, languages, etc.
Requirements
Design
Code
Test
January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
A Final Note on Reuse• The most important factor in
planning reuse is application domain– A series of products in the same
domain will get more reuse than a series of unrelated products
– And it will be easier to find what you need when you need it
– And the staff are more likely to be familiar with the old code and how it can be used again
Slide # 47 January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Summary of Size Estimating• History is your best ally• Use multiple methods
– to learn– to reduce risk
• Target memory size is handled differently from source code size, although the two are generally related
• Account for reuse
Slide # 48 January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
Module Summary• There are many special cases and
issues to consider when estimating size
• Reuse is accounted for by computing an equivalent size, based on the gains from reuse– These are estimated by conversion
factors based on past experience
Slide # 49 January 11, 2004
CSE 7315 - SW Project Management / Module 14 - Size Estimating Notes and
ReuseCopyright © 1995-2004, Dennis J. Frailey,
All Rights ReservedCSE7315M14
END OFMODULE 14