University of Southern California Center for Systems and Software Engineering

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Systems Engineering Reuse Principles

Jared Fortune, USC

Ricardo Valerdi, MIT

COSYSMO Workshop @ COCOMO Forum 2010

Los Angeles, CA

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 2.02

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

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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 driverx = {Easy, Nominal, Difficult}k = {Requirements, Interfaces, Algorithms, Scenarios}

Φ = quantity of “k” size driver E = represents (dis)economies of scaleEM = effort multiplier for the jth cost driver

University of Southern California Center for Systems and Software Engineering

Reuse CategoriesCategory Sub-Category Definition

I) New Products that are completely new

i) Designed for Reuse

Products that require an additional upfront investment to improve the potential reusability

II) Modified Products that are inherited, but are tailored

ii) Deleted Products that are removed from the system

III) Adopted 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• 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 improvedSeptember 10, 2009 7

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

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Academic COSYSMO 2.0(without reuse)

University of Southern California Center for Systems and Software Engineering

September 10, 2009 10

Academic COSYSMO 2.0(with reuse)