Requirements for Extremely Complex Systems

Product Camp Austin 16 - Requirements for Extremely Complex Systems

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Requirements for Extremely Complex

SystemsDavid Hetherington

2/13/2016


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Introducing the “System of Systems”


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Classic “System of Systems”

Multiple Levels

Each Level is a “System” in its own right.

Requirements at any level affect all the levels below.


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“System of Systems” Common Features

Mission-Critical “Five Nines” Availability Required

Multiple Suppliers

Software/Requirements mistakes can kill peopleSafety-Critical

Tower of Babel

Software/Requirements mistakes can cause huge financial losses

High Stakes


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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=mbse: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 computersMany “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=mbse: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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Humans and Complexity Management

How do We Manage Complexity?

Stage 1 Stage 3Stage 2

Stage 1 – Requirements in Our Head

Skilled Professionals Hate “Bureaucracy”

“Tell Me What You Need”

“I’ll Make it Happen!”

Not Scalable

Stage 2 – Requirements and Specification Documents

Requirements Requirements Requirements

Requirements

System Specification

Sub-System Specification



Component Specification Component

Specification Component Specification Component

Specification


Specification Component Specification


Specification Component Specification Component

Specification

CHANGE!!

Requirements


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Requirements Traceability

Traceability Matrices

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Standards Discovery

V0.4 – 3 January 2016

Euro Norm (2007)

Something Else (1982)

3rd Item (1967)

…Shall be compliant with XYZ Sections 3.4 and 7.8

…as laid out in Table x31.2 in…

Untangling this sort of mess leaves a spider web that does not fit neatly in a traceability matrix.

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Standards Analysis

V0.4 – 3 January 2016

Some Standard

“…shall automatically stop at pedestrian crossings if pedestrians are present.”

So…what does this standard actually require? A lot of analysis and interpretation will be required!


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Text-Only Requirements Tools


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Automate the Cut-and-Paste


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Semi-Automated document input

Drag-and-drop Easy output of

Word documents Good traceability

functions

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Strengths/LimitationsStrengths Weaknesses

Text-only is cumbersome

“A picture is worth a thousand words”

Requirements reviews are painful

Hard to link to other tools


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Model-Based Systems Engineering

Solution – Add Graphical Modeling to Text

DatabaseThe Database Keeps Track of the Relationships

Structure

Requirements

Behavior

Introducing Model-Based Systems Engineering

“Model-Based Systems Engineering” is the More Formal Term.

Database

Simple Diagrams

Different Diagrams for Different Stakeholders

As Many Diagrams as Needed

One Concept per Diagram

Model Database Consolidates Information

Structure ViewPlumbing View

Software View

Introducing SysML

Precise Diagrams

XML Model Data Representation


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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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Agile vs Safety-Critical


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Not Every Application Needs Careful Planning

Animation by Kalia Pickett


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Safety-Critical AppsIf a careless mistake in your requirements, coding, or verification can incinerate a crew of 150 people, it is immoral to “blow off the documentation”…


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Understanding the Role of MBSE

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Systems Model – NOT a PowerPoint Compiler

RequirementsRequirement

sRequirements

PicturesPictures

PicturesPictures

Pictures

PowerPoint

CompilerProduc

t


Systems Model – Tower of Babel

Wants range to be > 1km

MarketingVertical beam

pattern?

Antenna GuyTransmit Power?

Radio

How big is the test track?

Test Facility

FFT range bins?

Digital

Message format?

Firmware

Power Dissipation?

Thermal

PackageDesign?

Mechanical

“Make it

1000m”

“Seems to

be1000m”

“2048 point FFT”

“Rent an airport”

“20 wattradio”

“Need a big fan”


Systems Model – Single Version of Truth

Wants range to be > 1km

MarketingVertical beam

pattern?

Antenna GuyTransmit Power?

Radio

How big is the test track?

Test Facility

FFT range bins?

Digital

Message format?

Firmware

Power Dissipation?

Thermal

PackageDesign?

MechanicalRange =

182m

System Model


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Agile in a Complex Systems Environment


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Illusion of predictability

Elaboration too early

Long periods without working code

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First… We Need to Lose Some BaggageTraditional Side Agile Side

Moaning about “Waterfall”

Skipping the documentation

Flexible definition of “done”


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Precision Accountability Project Scale

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Next… Recognize Each Other’s StrengthsTraditional Side Agile Side

Frequent checkpoints reduce risk

Efficient management of uncertainty

Superior team throughput


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Road to Certain FailureCollect lots of requirements documents

Make beautiful “Logical” architecture model

Elaborate 20 levels of logical architecture and increasingly detailed requirements

Publish voluminous specifications based on above

Attempt to “allocate” logical architecture to real world subsystems

Discover that nothing works

Blame the tools!!


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Better ApproachExisting System

Model (Existing)

RequirementsReverse

Engineer

ElaborateAnd Allocate

Gaps

Model (New)

Try for Fit?

Agile Process

New System


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Reference


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David Hetherington

◦ LinkedIn: https://www.linkedin.com/in/djhetherington◦ GitHub: https://github.com/DavidHetherington◦ Dave’s “Minimal SaaS” Demo:

http://cities.asattepress.com/

2/13/2016

Contact

https://www.linkedin.com/in/djhetherington

https://www.linkedin.com/in/djhetherington

https://github.com/DavidHetherington

https://github.com/DavidHetherington

