Using SysML to Estimate Using SysML to Estimate SoS Engineering and SoS Engineering and

Development EffortDevelopment Effort

Jo Ann Lane (jolane@usc.edu)Tim Bohn (tbohn@us.ibm.com)

COCOMO Forum 2009

OverviewOverview

System of Systems (SoS) cost estimation overview

Systems Modeling Language (SysML) characterizations of SoS

Generating SoS cost model inputs from SysML views

Summary, conclusions, and future work

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Systems Engineering for Systems Engineering for Systems of Systems Systems of Systems

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SoS: A set or arrangement of systems that results when independent and useful systems are integrated into a larger system that delivers unique capabilities

Focus is on net-centric SoS…

SoSE Cost Model: Extension of COSYSMO SoSE Cost Model: Extension of COSYSMO Engineering Cost ModelEngineering Cost Model

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Size Drivers

Cost Factors

Estimated EngineeringEffort

Calibration

• Number of System Requirements• Number of System Interfaces• Number of Algorithms• Number of Operational Scenarios

• People characteristics• Process characteristics• Product characteristics

COSYSMO

SoSE cost model uses COSYSMO size drivers and cost factors

SoSE Capability Effort Calculation* SoSE Capability Effort Calculation*

Total Effort = SoSE effort + ∑ “affected CS”i effort

Specific constituent systems (CSs) depend upon alternative selected

CSi effort depends upon types of changes required for CSi

◦ New interface(s)/interface change(s)◦ Internal algorithm change(s)/data conversions

Size driver options◦ Number of requirements ◦ Number of algorithms◦ Number of interfaces ◦ Number of operational scenarios

Each size driver characterized with respect to complexity All size drivers converted to equivalent # of nominal reqs

5* See “backup charts” for details of lower-level SoSE calculations…

SoSE Estimation Steps for SoSE Estimation Steps for New CapabilityNew Capability1. Understand/review current CS capabilities2. Identify new capability alternatives3. For each alternative, identify

◦ CSs that contribute to each alternative◦ For each contributing CS, changes needed to support

alternative New interfaces/interface change(s) Data element/algorithm change(s) Capability size count(s) and associated complexity of each

4. Conduct alternative tradeoffs and finalize cost estimate for selected alternative

5. Identify CS changes required for desired architecture enhancements

6. Calculate COSYSMO effort multipliers at SoS and CS levels7. Calculate SoSE effort for alternative

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SoSE Estimation Steps for SoSE Estimation Steps for New CapabilityNew Capability1. Understand/review current CS capabilities2. Identify new capability alternatives3. For each alternative, identify

◦ CSs that contribute to each alternative◦ For each contributing CS, changes needed to support

alternative New interfaces/interface change(s) Data element/algorithm change(s) Capability size count(s) and associated complexity of each

4. Conduct alternative tradeoffs and finalize cost estimate for selected alternative

5. Identify CS changes required for desired architecture enhancements

6. Calculate COSYSMO effort multipliers at SoS and CS levels7. Calculate SoSE effort for alternative

7Focus of presentation

Primary SoS Core Elements Primary SoS Core Elements Determining SoSE Size Drivers Determining SoSE Size Drivers

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SoS: A set or arrangement of systems that results when independent and useful systems are integrated into a larger system that delivers unique capabilities

SysML Models for Characterizing SysML Models for Characterizing SoS/SoS CapabilitiesSoS/SoS Capabilities

Use cases◦ Characterize both CS and SoS

capabilities from the different user perspectives

Sequence diagrams◦ Characterize and analyze the

operational flow for an SoS capability

Object blocks◦ Characterize each SoS CS and

its capabilities

Interface classes◦ Describe each CS interface

Input/output entity classes◦ Express the associated data

attributes of each data item transferred over that interface

◦ May include units, coordinate system, reference frame, source algorithm, etc.

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Example SoS: Regional Area Example SoS: Regional Area Crisis Response SoS (RACRS)Crisis Response SoS (RACRS)

10Command Control Center (CCC) Context Diagram

Mission Scenarios: Use Cases and Mission Scenarios: Use Cases and Sequence DiagramsSequence Diagrams

CCC Interface Class andCCC Interface Class andEvacuate Area I/O Entities by ActorEvacuate Area I/O Entities by Actor

SoSE Estimation StepsSoSE Estimation Steps

Understand/review current CS capabilities

Identify capability alternatives

For each alternative, identify◦ CSs that contribute to

each alternative◦ CS changes needed to

support alternative

CS object class descriptions and context diagrams

Use cases and sequence diagrams

For each alternative

◦ Sequence diagrams

◦ Interface diagrams◦ I/O entity class descriptions

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Steps Supporting SysML Elements

Summary and ConclusionsSummary and Conclusions Initial SoSE cost model work used “# of reqs” as size

driverProspective users asked for guidance for using other

size driversShowed how to use SysML models to

◦ Evaluate alternatives◦ Estimate SoS size driver values

Given that focus is on net-centric SoSs, key SysML models used◦ Context diagrams ◦ Object blocks◦ Use cases ◦ Interface classes◦ Sequence diagrams ◦ I/O classes

Used to identify SoS interface and CS algorithm changes◦ Not clear usefulness of “operational scenario” size driver since

most SoS operational scenarios are typically complex, cross-cutting scenarios

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Summary and Conclusions Summary and Conclusions (continued)(continued)

Alternative size driver values still must be converted to “nominal requirements” for the COSYSMO calculations

When using developing/using models for an SoS, remember:◦ Each SoS is unique and the cost model needs to be

calibrated for the SoS and its constituents SoS level Each constituent system (since each one is typically

managed/maintained by a different organization) Complexity factors to convert all size driver values into “nominal

requirements” with respect to the local calibration◦ Only model what is necessary to capture and understand

the problem and its context…

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Continuing SoSE Cost Model Continuing SoSE Cost Model ResearchResearch

Looking for additional SoSs to refine cost model◦Model development◦Local calibration

Contact:Jo Ann Lanejolane@usc.edu

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ReferencesReferencesBohn, T., Nolan, B., Brown, B., Balmelli, L, Wahli, U. (2008);

Model Driven Systems Development with Rational Products, IBM Redbooks, DOI= http://www.redbooks.ibm.com/abstracts/SG247368.html?Open

Dahmann, J., Asrat, W., Rebovich, G., Lane, J., and Lowry, R. (2009); Results of M&S Committee Survey on M&S and SoS SE. In Proceedings of the August 13, 20009 Meeting of the National Defense Industrial Association (NDIA) Modeling and Simulation (M&S) Committee. DOI= http://www.ndia.org/Divisions/Divisions/SystemsEngineering/Pages/Modeling_and_Simulation_Committee.aspx

Department of Defense (DoD) (2008); Systems Engineering Guide for System of Systems, version 1.0. DOI= http://www.acq.osd.mil/sse/docs/SE-Guide-for-SoS.pdf

Object Management Group (2008); OMG System Modeling Language (SysML), version 1.1. DOI= http://www.omg.org/spec/SysML/index.htm

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Backup Charts

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SoS Effort CalculationsSoS Effort Calculations

SoSE Effort

SoSE Effort = 38.55*[((SoSCR/SoSTreq)*(SoSTreq)1.06 *EMSoS-CR)+ ((SoSMR/SoSTreq)*(SoSTreq)1.06 * EMSoS-MR)/152]

Where:

Total SoSE requirements = SoS Capability Requirements + SoS “Monitored” Requirements

SoS “monitored” reqs = [∑SE non-SoS requirements being addressed current upgrade cycles for all SoS constituent systems] * “Oversight Factor”

“Oversight Factor” between 5% and 15% (these values are based on the COSYSMO reuse work and expert judgment from various CSSE affiliates and the SoS SE Guidebook team)

SoS capability effort

Oversight of CSs

SoS Effort Calculations SoS Effort Calculations (continued)(continued)

Single Constituent System Effort

Total single system reqsw-SoSE = SoS requirements allocated to system + SE reqs in upgrade cycle

Single system SE Effort in an Acknowledged SoS

= 38.55*[1.15*( (SoSCSalloc / CSTreqSoSE)*( CSTreqSoSE)1.06* EMCS-CRwSOSE) +

(CSnonSoS / CSTreqSoSE)*( CSTreqSoSE)1.06* EMCSnonSOS] /152

Computed for each constituent system in the SoS...Approach is recursive:

Can also model each constituent system as a complex system or SoS...

SoS capability effort

Constituent system upgrade effort

CS “tax” to support SoSE team