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The Enterprise Engineering Series SeriesEditors JanL.G.Dietz ErikProper JoséTribolet EditorialBoard TerryHalpin JanHoogervorst MartinOp’tLand RonaldG.Ross RobertWinter Forothertitlespublishedinthisseries,goto www.springer.com/series/8371 Danny Greefhorst (cid:2) Erik Proper Architecture Principles The Cornerstones of Enterprise Architecture DannyGreefhorst ErikProper ArchiXLB.V. PublicResearchCentreHenriTudor NijverheidswegNoord60-27 29,avenueJohnF.Kennedy Amersfoort3812PM 1855Luxembourg-Kirchberg TheNetherlands Luxembourg [email protected] [email protected] Thepublicationofthisbookwassponsoredby: Inwritingthisbook,theauthorswerekindlysupportedby: ISBN978-3-642-20278-0 e-ISBN978-3-642-20279-7 DOI10.1007/978-3-642-20279-7 SpringerHeidelbergDordrechtLondonNewYork LibraryofCongressControlNumber:2011927926 ACMComputingClassification(1998): H.1,H.4,H.5,J.1,K.4.3,K.6.1 ©Springer-VerlagBerlinHeidelberg2011 Thisworkissubjecttocopyright.Allrightsarereserved,whetherthewholeorpartofthematerialis concerned,specificallytherightsoftranslation,reprinting,reuseofillustrations,recitation,broadcasting, reproductiononmicrofilmorinanyotherway,andstorageindatabanks.Duplicationofthispublication orpartsthereofispermittedonlyundertheprovisionsoftheGermanCopyrightLawofSeptember9, 1965,initscurrentversion,andpermissionforusemustalwaysbeobtainedfromSpringer.Violations areliabletoprosecutionundertheGermanCopyrightLaw. Theuseofgeneraldescriptivenames,registerednames,trademarks,etc.inthispublicationdoesnot imply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfromtherelevantprotective lawsandregulationsandthereforefreeforgeneraluse. Coverdesign:deblik Printedonacid-freepaper SpringerispartofSpringerScience+BusinessMedia(www.springer.com) Foreword Whenenterprisearchitectstrytoexplaintopeoplewhoarenotenterprisearchitects what it is they do for a living, they almost invariably resort to using an analogy with the architecture of buildings, and describe enterprise architecture as a ‘kind of blueprint’. While this analogy may be helpful in conveying a general sense of what the discipline of enterprise architecture is ‘sort of like’, it can be seriously misleadingiftakentooliterally. Despite this risk, far too much thinking about enterprise architecture has been undulyinfluencedbythisanalogy.Thisisnotsurprising;afterall,itiscalled‘archi- tecture’,anditisreasonabletoexpectthatiftwodisciplinesshareanimportantpart oftheirname,theymustsharealotofotherstuffaswell.Unfortunately,theydonot. Buildingsandenterprisesarequalitativelydifferentkindsofartifacts.Probablythe biggestdifferenceisthewaypeoplerelatetothem.Peopledonotjustuseorinteract withanenterprise:peoplearetheenterprise. Minimizing,ifnotentirelyignoring,thisdifference,whetherdeliberatelyorin- advertently,makestheproblemofenterprisedesignseemtractable,inthatitcanbe thoughtofasamatterofdraftingtherightkindofblueprint.Hence,mostdefinitions of architectureas appliedto what must be thought of as people-intensivesystems, areinherentlystructuralinnature,andarchitecturesarethoughtofasbeingderived viaandrepresentedbymodels.Theideathatarchitectureisprimarilyaboutstruc- ture,andtheideathatarchitectureisbestrepresentedbymodels,mutuallyreinforce oneanother.Mostarchitecturalmodelsarerepresentedby‘boxesandlines’,andit ishardnottothinkofwhatisdepictedassomekindofstructure. This is ironic, because the earliest well documented use of the word ‘architec- ture’inanITcontextwastodescribetheprogrammervisiblebehavioroftheIBM System/360familyofprocessors,inamannerindependentoftheinternalstructure oftheimplementation. Theemphasis,ifnotexclusivefocus,onstructureastheconcernofarchitecture leadstoanevenmoreperniciousconsequence:divorcingthearchitectureofasys- temfromitsraisond’être.Modelsareverygoodatrepresentingthewhatandhow ofasystem,buttheyleavethewhyimplicitandexternaltothemodel,andthus,too often,externaltothearchitecture.Thismakesitfartooeasytothinkofthesystem asanendinitself,ratherthanasameanstoachievingsomemission. v vi Foreword When I joined the Architecture Profession Office of HP Services in 2001, I learned HP’s architecture method, which later became known as HP Global Method for IT Strategy and Architecture (ITSA). Until then I had been doing ar- chitecturebytheseatofmypants,andITSAwasarevelation.TheessenceofITSA isusingalinkedsuccessionofarchitecturalprinciplestoprovideachainofmotiva- tionandjustificationfromthebusinesscontextoftheproblem,needoropportunity totheconstraintsonimplementationandoperationnecessarytoensurethesolution delivers the required business value. In ITSA, models, while important, are sec- ondarytoprinciples;indeed,ITSApractitionersaretaughtthatmodelsarederived from principles, and ideally every element of a model illustrates some principle. Thischainofmotivationandjustificationnotonlyensuresalignmentofthesolution withtheneedsofthebusiness,italsoprovidestraceabilityandanobjectivecontext forgovernance. TherecentlypublishedbookabouttheITSAmethodshowedtheimportantrole principlescanplayinthedevelopmentofanarchitecture.ThisnewbookbyDanny andEriktakesthenextstepbyprovidinganindepthtreatmentofprinciples,anda conceptualframeworkforthinkingaboutthem.Architecturalprinciplesarefinally getting the well deserved attention they have too long lacked. I am confident that somedaywewilllookbackonthisasawatershedeventintheprofessionalization andmaturingofthedisciplineofenterprisearchitecture. LeonardFehskens VP,SkillsandCapabilities TheOpenGroup Preface Enterprises,fromsmalltolarge,evolvecontinuously.Asaresult,theirstructuresare transformedandextendedcontinuously.Withoutsomemeansofdeliberatecontrol, suchchangesareboundtoleadtoanoverlycomplex,uncoordinatedandheteroge- neous environment that is hard to manage, while at the same time resisting future changesindesireddirections.Enterprisearchitectureaimstoprovidesuchcontrols. Keyconceptsinenterprisearchitectureincludestakeholdersandtheirconcerns, architecture principles, models, views and frameworks. While most of these con- ceptshaveobtainedampleattentioninresearch,theconceptofarchitectureprinci- ples has not been studied much yet. More specifically,architecture principles pro- vide a means to direct transformations of enterprises. As a consequence, it can be arguedthatarchitectureprinciplesformthecornerstonesofanyarchitecture.Inthis book, we therefore specifically focus on the role of architecture principles. It pro- vides both a theoretical and a practical perspective on architecture principles. As suchitistargetedatstudentsandresearchers,aswellaspractitionerswhohavethe desiretounderstandthefoundationsunderlyingtheirpracticalwork. Thetheoreticalperspectiveinvolvesabriefsurveyofthegeneralconceptofprin- ciple as well as an analysis of different flavors of principles. A key distinction is made between scientific principles and normative principles. Scientific principles arelawsorfactsofnatureandformthefundamentaltruthsthatonecanbuildupon. Normativeprinciplesarerulesofconductthatguide/restrictbehavior.Whilescien- tificprincipleshold“naturally”,normativeprinciplesneedexplicit“enforcement”. Architectureprinciples,beingthecoretopicofthisbook,areregardedasaspecific classofnormativeprinciplesthatinfluence/directthedesignofanenterprise(from thedefinitionofitsbusinesstoitssupportingIT). The practical perspective on architecture principles is concerned with an ap- proach for the formulation of architecture principles, as well as their actual use in organizations.Toillustratetheiruseinpractice,severalreallifecasesarediscussed. Furthermore, the book includes an appendix, which provides a discussion on how to use the suggested approach for the formulation and application of architecture principles in the context of The Open Group’s TOGAF, as well as a catalogue of examplearchitectureprinciples. vii Acknowledgements Thecreationofthisbookwouldnothavebeenpossiblewithoutthecontributionof others. In particular, many of the ideas have been based on discussions we had in the architecture principles working group of the Netherlands Architecture Forum (NAF). We would especially like to thank Louis Dietvorst and Pieter Buitenhuis fortheirvaluablecontributions.OurthoughtsarealsowithLeoHermans,whocon- tributedenthusiasticallytotheworkinggroup,buthasregretfullypassedaway.We alsothankthestudentswhojoinedtheworkinggroupandcontributedtotheconcep- tualframeworkwiththeirmasterthesis:MartijnvandenTillaart,KoenvanBoekel, NielsvanBokhoven,TeunHuijbers,HarryvandenWollenbergandJordyKersten. We would also like to thank the people that contributed content to the book, such as case descriptions. Our book would not have been as valuable without the contributionsofCharlesHendriks,JoostPeetoom,ErikKiel,AnneMarievanRooij, RonaldvandenBerg,PeterBergman,ErikSaaman,BennyPrijandLouisDietvorst. Wealsothankallthepeoplethatrevieweddraftversionsofthebookandprovided us with important feedback: Christian Fischer, Dirck Stelzer, Eric Schabell, Erik Vermeulen,ErikSaaman,ErwinOord,FrankHarmsen,JanDietz,JanHoogervorst, Joost Lommers, José Tribolet, Marc Lankhorst, Mathias Ekstedt, Monika Grün- wald,PeterBeijer,PontusJohnson,RaymondSlotandRemcodeBoer.Veryspecial thanksgotoJoostLommersandPeterBeijerfortheirelaboratereviewcomments. WewouldliketoexplicitlythankLenFehskensforbeingasourceofinspirationfor ourbook,forprovidinginsightsontheessenceofarchitecture,andforwritingthe foreword. Finally, we would also like to thank our respective employers, ArchiXL, The NetherlandsandthePublicResearchCentreHenriTudor,Luxembourg,aswellas theFondsNationaldelaRechercheLuxembourgandtheNetherlandsArchitecture Forum,insupportingthecreationandpublicationofthisbook. Amersfoort,TheNetherlands DannyGreefhorst Luxembourg-Kirchberg,Luxembourg ErikProper ix Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 ChallengestoEnterprises . . . . . . . . . . . . . . . . . . . . . . 1 1.2 EnterpriseArchitectureandArchitecturePrinciples . . . . . . . . 3 1.3 MotivationsandTargetAudience . . . . . . . . . . . . . . . . . 4 1.4 OutlineoftheBook . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 TheRoleofEnterpriseArchitecture . . . . . . . . . . . . . . . . . . 7 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.2 EnterpriseTransformationsandEnterpriseEngineering . . . . . . 9 2.3 StreamsofActivitiesinEnterpriseEngineering . . . . . . . . . . 11 2.4 Architecture-BasedGovernanceofEnterpriseTransformations . . 14 2.4.1 TheNeedforArchitecture . . . . . . . . . . . . . . . . . 14 2.4.2 ArchitectureasaBridgefromStrategytoDesign . . . . . 16 2.4.3 SteeringwithArchitecture . . . . . . . . . . . . . . . . . 18 2.4.4 TheThreeRolesofEnterpriseArchitecture . . . . . . . . 19 2.5 DefiningEnterpriseArchitecture . . . . . . . . . . . . . . . . . . 20 2.5.1 ThePurposeofanEnterpriseArchitecture . . . . . . . . . 21 2.5.2 TheMeaningofanEnterpriseArchitecture . . . . . . . . 22 2.5.3 TheElementsofanEnterpriseArchitecture . . . . . . . . 22 2.5.4 DefinitionofEnterpriseArchitecture. . . . . . . . . . . . 24 2.6 OtherFormsofArchitecture . . . . . . . . . . . . . . . . . . . . 24 2.7 StandardsforEnterpriseArchitecture . . . . . . . . . . . . . . . 26 2.8 TheRoleofArchitecturePrinciples . . . . . . . . . . . . . . . . 28 2.9 KeyMessages. . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3 AConceptualFrameworkforPrinciples . . . . . . . . . . . . . . . . 31 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 3.2 BackgroundofArchitecturePrinciples . . . . . . . . . . . . . . . 32 3.3 KeyClassesofPrinciples . . . . . . . . . . . . . . . . . . . . . . 34 3.3.1 ScientificPrinciples . . . . . . . . . . . . . . . . . . . . 34 3.3.2 DesignPrinciplesasNormativePrinciples . . . . . . . . . 35 3.3.3 FromCredostoNorms . . . . . . . . . . . . . . . . . . . 38 xi xii Contents 3.3.4 ConceptualFramework . . . . . . . . . . . . . . . . . . . 40 3.4 ArchitecturePrinciplesasPillarsfromStrategytoDesign. . . . . 44 3.4.1 ArchitecturePrinciples . . . . . . . . . . . . . . . . . . . 44 3.4.2 BusinessandITPrinciples . . . . . . . . . . . . . . . . . 44 3.4.3 BridgingfromStrategytoDesign . . . . . . . . . . . . . 46 3.4.4 ExtendedConceptualFramework . . . . . . . . . . . . . 48 3.5 MotivatingArchitecturePrinciples . . . . . . . . . . . . . . . . . 49 3.5.1 SourcesforFindingMotivation . . . . . . . . . . . . . . 50 3.5.2 DriversasMotivationforArchitecturePrinciples . . . . . 52 3.5.3 ExtendedConceptualFramework . . . . . . . . . . . . . 54 3.6 FormalSpecificationofNormativePrinciples . . . . . . . . . . . 56 3.7 KeyMessages. . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 4 ArchitecturePrincipleSpecifications . . . . . . . . . . . . . . . . . . 59 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4.2 DimensionsinArchitecturePrinciples . . . . . . . . . . . . . . . 62 4.2.1 TypeofInformationDimension . . . . . . . . . . . . . . 63 4.2.2 ScopeDimension . . . . . . . . . . . . . . . . . . . . . . 63 4.2.3 GenericityDimension . . . . . . . . . . . . . . . . . . . 64 4.2.4 LevelofDetailDimension(s). . . . . . . . . . . . . . . . 65 4.2.5 StakeholderDimension . . . . . . . . . . . . . . . . . . . 66 4.2.6 TransformationDimension . . . . . . . . . . . . . . . . . 66 4.2.7 QualityAttributeDimension . . . . . . . . . . . . . . . . 67 4.2.8 Meta-levelDimension . . . . . . . . . . . . . . . . . . . 69 4.2.9 RepresentationDimension . . . . . . . . . . . . . . . . . 69 4.3 Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 4.3.1 BasicStructure . . . . . . . . . . . . . . . . . . . . . . . 71 4.3.2 AdvisedAttributes . . . . . . . . . . . . . . . . . . . . . 73 4.3.3 AttributesforClassification . . . . . . . . . . . . . . . . 75 4.3.4 PotentialAttributes . . . . . . . . . . . . . . . . . . . . . 75 4.3.5 GenericMeta-dataAttributes. . . . . . . . . . . . . . . . 76 4.3.6 Relationships . . . . . . . . . . . . . . . . . . . . . . . . 77 4.4 ArchitecturePrincipleSets . . . . . . . . . . . . . . . . . . . . . 79 4.5 QualityCriteria . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 4.6 KeyMessages. . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 5 APracticalApproach . . . . . . . . . . . . . . . . . . . . . . . . . . 85 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 5.2 GenericProcess . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 5.2.1 DetermineDrivers . . . . . . . . . . . . . . . . . . . . . 88 5.2.2 DeterminePrinciples . . . . . . . . . . . . . . . . . . . . 91 5.2.3 SpecifyPrinciples . . . . . . . . . . . . . . . . . . . . . 98 5.2.4 ClassifyPrinciples . . . . . . . . . . . . . . . . . . . . . 100 5.2.5 ValidateandAcceptPrinciples . . . . . . . . . . . . . . . 100 5.2.6 ApplyPrinciples . . . . . . . . . . . . . . . . . . . . . . 101 5.2.7 ManageCompliance . . . . . . . . . . . . . . . . . . . . 105

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