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DevelopingInformationSystems
Inthisandthefollowingchapters,wewilldiscussdifferentapproachesconcerninghowanorganizationcanobtainitsinformationsystemsoncethedecisioninfavorofasystemhasbeenmade.
Whilechapter7willdealwithbuyingandintroducingsoftwarethatwasdevelopedbyothers,inparticularstandardsoftware,thefocusinthischapterisonhowtobuildcompletelynewinformationsystemsornewmodulesthatextendexistinginformationsystemswithinanorganization.By"
newmodules"
wemeanthatsignificantdevelopmenteffortisrequiredinorderfortheprojecttopassallstagesofthesoftwaredevelopmentprocess.
Incontrasttothis,limitedextensionsofarunninginformationsystemareconsideredpartofthemaintenanceandsupportstages.Addingfunctionalitytoanewstandardsoftwaresystemwillbediscussedinchapter7,aspartofthecustomizingprocess.
Theperspectivetakeninthischapteristhatthestartingpointforthedevelopmenteffortisanapprovedprojectproposal(cf.section2.2.1);
i.e.,amanagerialleveldecisiontolaunchaprojectforbuildingasysteminhousehasbeenmade.Ifnorestrictionsexisted,wecouldsaythattheprojectstartsfromscratch.Intherealworld,however,suchrestrictionsoftenlimitthedegreesoffreedomsubstantially.
4.1StartingwithaProblemSpecification
Constraintsthatanewinformationsystemdevelopmenteffortmayneedtoobserveincludethefollowing:
–Theexistinginformationsystemslandscapehastobeconsidered.Mostlikelythenewsystemwillneedtobeinterfacedwiththecompany'
sERPsystemandotherinformationsystems.
–Theplatformonwhichthenewsystemwillrunisprobablyoutsidethescopeoftheproject.Ifthecompany'
sexistingsystemsareallbasedonIBMWebSphere,forexample,thenitisunlikelythatadifferentplatformwillbechosenforanewsystemwhichneedstobeintegrated.
–Dependingonhowcloselythesystemistobeconnectedwithexistingsystems,itsarchitecturemayalreadybepredetermined,i.e.,itmayhavetomatchthearchitectureoftheothersystems.
–Manyprojectshavetorununderatightbudgetandmeagerstaffing,limitingthepossibilitiesofwhatcanbedone.
Despitetheseconstraints,thedevelopmentofnewinformationsystemsoffersawidearrayofoptionsandfewerlimitationsthancustomizationprojects.
Anydevelopmentprojectneedsaspecificationoftheproblemstobetackled.Theprojectproposalcontainsaproblemdescription,butthisdescriptionisusuallyjustawrittentextfortheapprovalprocess,toocoarseandnotoperationalenoughtoidentifyrelevantdevelopmenttasks.Forthispurpose,amoreformalizedhigh-levelspecificationofthefuturesystemisrequired.
Severalapproachestodefinesuchhigh-levelspecificationshaveemergedinthepast.Withbusinessprocessesnowadaysbeingthedominatingparadigmforrunningorganizations,thishigh-leveldescriptionoftheISneedsisusuallyadescriptionofabusinessprocessorasub-process.
Theprocessspecificationcouldsimplybeatextualdescriptionofthemajorprocessstepsandtheresourcesinvolved.Sincesemi-formalspecificationshaveadvantagesovertext,variousgraphicalnotationstospecifyabusinessprocessonahighlevelhavecomeintoexistenceovertheyears,includingthefollowing:
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ContextdiagramsinSA(structuredanalysis)[Yourdon1989,p.339]
Activityanduse-casediagramsinUML(unifiedmodelinglan¬
guage)
Event-drivenprocesschainsinARIS(architectureofintegratedinformationsystems)[Scheer2005]
BusinessprocessdiagraminBPMN(businessprocessmanage¬
mentnotation)
Figure4-1showsjustonepossiblewayofvisualizingabusinesspro¬
cess.Asmanynotationsforbusiness-processmodelingexist,thegraphicalconstructsvary.Besideshigh-leveldiagrams,allapproachescompriseasuiteofgraphicalsymbolswithappropriatesemanticsaswellasmethodsandtoolsfordifferentaspectsofmodelingandcon¬
struction.Asaprocessisincreasinglyrefined,moresymbolsandmoremeaningsareaddedtothehigh-levelrepresentation.Sincemethodsand
toolswillbediscussedinthefollowingchapter,wedonotintroducemorenotationsatthispoint.
4.2ProcessModelsandISDParadigms
Assumingthatanoperationalproblemspecificationhasbeencreated,developmentoftheinformationsystemcanstart.Therearemanywaystoconductthedevelopmenteffort.Templatesarrangingdevelopmentactivitiesintoaspecifiedorderarecalledsoftwareprocessmodels.(Notethattheterm"
process"
refersheretosoftwaredevelopmentactivitiesandnottobusinessprocessesasabove.)Thistermcanbedefinedasfollows:
Asoftwareprocessmodelisanorderedsetofactivitieswithasso¬
ciatedresultsthatareconductedintheproductionandevolutionofsoftware.Itisanabstractrepresentationofatype