Short presentation delivered at Product Camp Austin 24 in Austin, TX on 22 Feb 2020. Intended to educate product management professionals on the fundamentals of model-based systems engineering for safety-critical and complex systems.

1. 1
David Hetherington
SYSTEM STRATEGY,
INC.
Principal
dhetherington@designxi.com
Requirements Management for Safety-Critical
Products
SOLUTIONS FOR COMPLEX SYSTEMS
2/22/2020 © 2020 SSI

2. In Kind
Advocate
Sponsors
SUPPORTERS

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So… What are We Talking About?

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Not Every Application Needs Careful Planning
Copyright 2016 Asatte Press, Inc – Used with Permission
If you are developing a
“Cat Eating
Cheeseburger” social
media application,
overly formal
requirements
approaches would be
counter-productive.

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Safety-Critical Apps
Licensed from Shutterstock by David Hetherington on 17 Feb 2020
If a careless mistake in
your requirements,
coding, or verification
can incinerate a family
of five, casual
requirements
management
approaches are simply
not morally acceptable.

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Text-Only Requirements Tools

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Text-Oriented Requirements Database Systems
Siemens Polarion
IBM DOORS NG

8. 1000 10,000 100,000100
Pain Level
Number of Requirements (Using only text-based tools)
tolerable
painful
excruciating
human
rights
violation
The Problem with Text-Oriented Requirements Tools
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Copyright 2019 Asatte Press, Inc – Used with Permission
tolerable
painful
excruciating
Human
rights
violation

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How Complicated do Such Systems Get?

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Ford Example – Car Complexity
http://www.omgwiki.org/MBSE/lib/exe/fetch.php?media=m
bse:03-2013_incose_mbse_workshop-
ford_automotive_complexity_v4.0-davey.pdf
Presentation of Christopher Davey at the
INCOSE International Workshop MBSE
Workshop January 26th-28th, 2013
A luxury car can have more than
100 onboard computers
Many “requirements” need
multiple onboard computers to
cooperate with each other in a
tightly choreographed dance.

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Ford Example – 450,000 Requirements
http://www.omgwiki.org/MBSE/lib/exe/fetch.php?media=m
bse:03-2013_incose_mbse_workshop-
ford_automotive_complexity_v4.0-davey.pdf
Presentation of Christopher Davey at the
INCOSE International Workshop MBSE
Workshop January 26th-28th, 2013
Working out all that
choreography
produces 450,000
requirements.

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Model-Based Systems Engineering and SysML

13. Solution – Add Graphical Modeling to Text
The Database Keeps Track of the Relationships
Structure
Requirements
Behavior

14. Introducing Model-Based Systems Engineering
“Model-Based Systems Engineering” is the More Formal Term.
Simple Diagrams
Different Diagrams for
Different Stakeholders
As Many Diagrams as
Needed
One Concept per Diagram
Model Database
Consolidates Information
Structure View
Plumbing View
Software View

15. Solution – SysML Approach
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SysML (“Systems
Modeling Language”) is
the premier language for
modeling complex
systems-of-systems.
SysML provides a precise abstract and
concrete syntax to model complex systems. It
provides 9 standard diagrams to represent
aspects of any kind of system at an abstract,
interdisciplinary level.

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SysML – System Structure

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The Market Requirements

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The Safety Requirements

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Elaborating the Requirements

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Modeling Behavior

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Trace to Test Cases

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Requirements Traceability

23. Traceability Matrices

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The Single Version of the Truth

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Systems Model – Tower of Babel
Wants range to
be > 1km
Marketing
Vertical beam
pattern?
Antenna Guy
Transmit Power?
Radio
How big is the
test track?
Test Facility
FFT range bins?
Digital
Message
format?
Firmware
Power
Dissipation?
Thermal
Package
Design?
Mechanical
“Make it
1000m”
“Seems to
be1000m”
“2048
point
FFT”
“Rent an
airport”
“20 watt
radio”
“Need a big
fan”

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Systems Model – Single Version of Truth
Wants range to
be > 1km
Marketing
Vertical beam
pattern?
Antenna Guy
Transmit Power?
Radio
How big is the
test track?
Test Facility
FFT range bins?
Digital
Message
format?
Firmware
Power
Dissipation?
Thermal
Package
Design?
Mechanical
Range = 182m
System Model

27. Summary
For complex and safety-critical systems:
1. Casual requirements management approaches are not acceptable.
2. Air-tight traceability is mandatory.
3. The number of requirements make spreadsheets and other home-grown
approaches impractical.
4. Model-based systems engineering (MBSE) and SysML can help cut through
the complexity.
5. Above ~1,000 requirements, a database-driven requirements tool will be
needed.
6. Above ~10,000 requirements, both a database-driven requirements tool and
also SysML modeling working in tandem will be needed.
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28. Questions?
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David Hetherington
SYSTEM STRATEGY,
INC.
Principal
dhetherington@designxi.com
SSI is a privately held professional
solutions firm headquartered in Metro
Detroit. Our engagements include
small to large Fortune 500
businesses and the government. We
partner with clients to design and
institutionalize solutions for complex
systems.
CONTACT INFORMATION
System Strategy, Inc.
Velocity Collaboration Center
6633 Eighteen Mile Road, Suite 4C
Sterling Heights, MI 48314
T: 844.SYSTEMX
F: 844.SYSTEM0
info@systemxi.com
http://www.systemxi.com
Send questions to:
dhetherington@designxi.com