GSN - The Goal Structuring Notation: A Structured Approach to Presenting Arguments

207 Pages·2012·0.9 MB·English

by  John Spriggs (auth.)

GSN—The Goal Structuring Notation

John Spriggs
GSN—The Goal Structuring
Notation
A Structured Approach to Presenting
Arguments
123
JohnSpriggs
HaylingIsland
UK
e-mail: [email protected]
ISBN 978-1-4471-2311-8 e-ISBN978-1-4471-2312-5
DOI 10.1007/978-1-4471-2312-5
SpringerLondonDordrechtHeidelbergNewYork
BritishLibraryCataloguinginPublicationData
AcataloguerecordforthisbookisavailablefromtheBritishLibrary
LibraryofCongressControlNumber:2011940782
(cid:2)Springer-VerlagLondonLimited2012
The Extrasolar Planets Encyclopaedia Version:2.06 Maintainedby (cid:2) 2011JeanSchneider(CNRS-
LUTH,ParisObservatory)
SETI Institute: Unless otherwise indicated, the documents and graphics stored on this Web server,
www.seti.org,arecopyrighted.Linkstothesedocumentsarepermittedandencouraged.Nocopiesmay
bemadewithoutpermissionSETIInstituteCopyright(cid:2)2011.
BBC(cid:2)TheBritishBroadcastingCorporationBroadcastingHouse,PortlandPlace,London,W1A1AA
Apart from anyfair dealing for the purposes of researchor privatestudy, or criticismor review,as
permittedundertheCopyright,DesignsandPatentsAct1988,thispublicationmayonlybereproduced,
stored or transmitted, in any form or by any means, with the prior permission in writing of the
publishers,orinthecaseofreprographicreproductioninaccordancewiththetermsoflicensesissued
bytheCopyrightLicensingAgency.Enquiriesconcerningreproductionoutsidethosetermsshouldbe
senttothepublishers.
Theuseofregisterednames,trademarks,etc.,inthispublicationdoesnotimply,evenintheabsenceof
aspecificstatement,thatsuchnamesareexemptfromtherelevantlawsandregulationsandtherefore
freeforgeneraluse.
The publisher makes no representation, express or implied, with regard to the accuracy of the
informationcontainedinthisbookandcannotacceptanylegalresponsibilityorliabilityforanyerrors
oromissionsthatmaybemade.
Coverdesign:eStudioCalamarS.L.
Printedonacid-freepaper
SpringerispartofSpringerScience+BusinessMedia(www.springer.com)
TomywifeBonnie,whooncesaidthatevery
book should be dedicated to someone special

Preface
Motivation
I have often been asked over the last decade, or so, ‘Can you recommend a book
on GSN?’ My answer has always (well, up to now at least) been, ‘No’.
ThiswasnotbecauseIfoundallsuchbooksunworthy;ratheritisbecauseIhad
not found any books on the subject. When someone asked me the question just
after I had given a tutorial on GSN, I gave my stock answer. They came straight
back and said that I should write one.
So, after much delay, here it is.
ThisbookisbothfortheaspiringwriterofargumentsinGSNandforthosewho
wish to read, review and understand them. It presents a clear exposition of the
notation; it is a narrative, starting from first principles and showing why each
symbolisneededandhowitshouldbeused.Eachchapterbuildsonwhathasgone
before. This is not a learned dissertation; it is a practitioners’ guide to GSN, the
Goal Structuring Notation.
Important Notes
The purpose of this book is to give an introduction to the Goal Structuring
Notation and its use in representing arguments. It does not present any ready-to-
use arguments for redeployment elsewhere. In particular, it does not present any
safety arguments for re-use. A safety argument depends not only on the detail of
thethingarguedabout,butalsoupontheenvironmentinwhichitisused.Asafety
argument requires careful thought and analysis of the pertinent risks. If you ever
re-use parts of such arguments, or claim benefit from someone else’s argument,
add an explicit justification of why you think it is appropriate for use in the new
context.
The graphic illustrations appearing in this book are conceptual and were
developed strictly to support discussions in the text. They are not intended to be
used as the basis of assurance arguments. A number of the examples refer to
legislation or to regulatory requirements, but note that this book does not offer
legal advice; neither does it recommend means of compliance.
vii
viii Preface
The author of this book, his past and present employers and clients, and his
publishersshareneitherliabilitynorresponsibilityforanylossordamagedcaused,
or alleged to have been caused, by information obtained from this book.
Acknowledgments
TheGoalStructuringNotationwasformalisedforuseasameansofpresenting
safety arguments by Tim Kelly at York University.
Dr.KellyisstillsupervisingGSNdevelopmentbyhisstudentsandcolleagues,
both at York University and in industry. He has a web-page listing his many
publications on the topic at http://www-users.cs.york.ac.uk/*tpk/.
IlargelybasedtheextendedexampleofChaps.10,11and12ofthisbookona
presentation that I gave on 20th January 2009 to the Solent Branch of the Safety
and Reliability Society, SaRS, http://www.sars.org.uk/. Thank you to them for
giving me the opportunity to judge the interest in this topic and to see if the
examplewasstraightforwardenoughtobeilluminatingwithoutbeingsosimpleas
to be dull. Note: I am indebted to The South Downs Planetarium and Science
CentreinChichester,UK,forintroducingmetothesubjectofthisexample.They
have a web-site at http://www.southdowns.org.uk/sdpt/.
Of course, many thanks are also due to Anthony Doyle, Christine Velarde,
Claire Protherough, Grace Quinn and all their colleagues at Springer who made
this book possible.
July 2011 John Spriggs
Contents
1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 What is the Purpose of This Book?. . . . . . . . . . . . . . . . . . . 1
1.2 What is the Purpose of GSN; Who Would Use It?. . . . . . . . 2
1.3 How Should I Use This Book?. . . . . . . . . . . . . . . . . . . . . . 2
1.4 Important Note. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.5 Other Notations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.6 Questions and Problems . . . . . . . . . . . . . . . . . . . . . . . . . . 4
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Goals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1 What is a Goal?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2 The Top Goal: Declaring the Proposition . . . . . . . . . . . . . . 8
2.3 Subverting a Proposition . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.4 How do Goals Make Arguments?. . . . . . . . . . . . . . . . . . . . 9
2.5 Question . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.6 Problems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3 Contextual Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.2 Context. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.3 Context is Important . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.4 Environmental Context . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.5 Make External References Using Context . . . . . . . . . . . . . . 14
3.6 Further to Problems Set in Chapter 2 . . . . . . . . . . . . . . . . . 14
3.7 Avoid the Pitfall of Too Much Context. . . . . . . . . . . . . . . . 15
3.8 The Model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.9 Is There More Context?. . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.10 Question . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.11 Problems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
ix