University of Southern California
Center for Systems and Software Engineering
Systems Engineering
Reuse Principles
Jared Fortune, USC
Ricardo Valerdi, MIT
COSYSMO Workshop @
COCOMO Forum 2010
Los Angeles, CA
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University of Southern California
Center for Systems and Software Engineering
Need to Estimate Effect of Systems
Engineering Reuse
• Practitioners noted large errors between model estimates and
actuals
– Variations discovered to be attributable to programs with reuse
• Systems engineering reuse
– The utilization of systems engineering products from previous efforts
– Ex: architectures, requirements, test plans, interfaces
– Means of reducing cost, schedule, and/or risk
• Current version of the model assumes all systems engineering
products will be “built from scratch”
– Unable to account for the impact of systems engineering reuse
…COSYSMO 2.0
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University of Southern California
Center for Systems and Software Engineering
COSYSMO 2.0 Operational Concept
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University of Southern California
Center for Systems and Software Engineering
Model Form
Where:
PMNS = effort in Person Months (Nominal Schedule)
A = calibration constant derived from historical project data
wr = weight for reuse category
r = {New, Designed for Reuse, Modified, Deleted, Adopted,
Managed}
wx,k = weight for size driver
x = {Easy, Nominal, Difficult}
k = {Requirements, Interfaces, Algorithms, Scenarios}
Φ = quantity of “k” size driver
E = represents (dis)economies of scale
EM = effort multiplier for the jth cost driver
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University of Southern California
Center for Systems and Software Engineering
Reuse Categories
Category
Sub-Category
I) New
Definition
Products that are completely new
i) Designed for
Reuse
II) Modified
Products that require an additional upfront
investment to improve the potential reusability
Products that are inherited, but are tailored
ii) Deleted
III) Adopted
Products that are removed from the system
Products that are incorporated unmodified (a.k.a.
“black box” reuse)
iii) Managed
Products that are incorporated unmodified and with
minimal testing
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University of Southern California
Center for Systems and Software Engineering
Reuse Category Weights
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University of Southern California
Center for Systems and Software Engineering
COSYSMO 2.0 Implementation Results
Actual Systems Engineering Effort
Estimates with COSYSMO (no reuse categories)
R² = 0.50
Estimated Systems Engienering Size (equivalent requirements)
Actual Systems Engineering Effort
Estimates with COSYSMO 2.0 (with five reuse
categories)
R² = 0.72
September
2009
Estimated 10,
Systems
Engineering Size (equivalent requirements)
• Across 44 projects at 1
diversified organization
• Using COSYSMO:
–
–
–
–
PRED(.30) = 14%
PRED(.40) = 20%
PRED(.50) = 20%
R2 = 0.50
• Using COSYSMO 2.0:
–
–
–
–
PRED(.30) = 34%
PRED(.40) = 50%
PRED(.50) = 57%
R2 = 0.72
• Result: 36 of 44 (82%)
estimates improved
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University of Southern California
Center for Systems and Software Engineering
Reuse Framework
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University of Southern California
Center for Systems and Software Engineering
Academic
COSYSMO 2.0
(without reuse)
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University of Southern California
Center for Systems and Software Engineering
Academic
COSYSMO 2.0
(with reuse)
September 10, 2009
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