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A REVERSE ENGINEERING METHODOLOGY FOR DATA

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AREVERSEENGINEERINGMETHODOLOGYFORDATA

PROCESSINGAPPLICATIONS

KitKamper

r

SSpencerRugabe

choolofInformationandComputerScience

Sand

oftwareEngineeringResearchCenter

GeorgiaInstituteofTechnology

Atlanta,Georgia30332-0280

(404)894-8450

ABSTRACT

m

fReverseengineeringproducesahigh-levelrepresentationofasoftwaresyste

romalow-levelone.Thispaperdescribesamethodologyforreverseengineering

d

dthatconstructsanarchitecturaldesignforasystemfromitssourcecodeandrelate

ocumentation.Themethodologymakesuseofseveraltechniquesnormallyuseddur-

cingtheforwardsoftwaredevelopmentprocessaswellasanewtechniquecalledSyn-

hronizedRefinement.SynchronizedRefinementisasystematicapproachtodetecting

odesigndecisionsinsourcecodeandrelatingthedetecteddecisionstothefunctionality

fthesystem.Examplesaregivendemonstratingtheapplicationofthemethodology

tothereverseengineeringofaproductionsoftwaresystem.

4March9,199AREVERSEENGINEERINGMETHODOLOGYFORDATA

PROCESSINGAPPLICATIONS

KitKamper

r

SSpencerRugabe

choolofInformationandComputerScience

Sand

oftwareEngineeringResearchCenter

GeorgiaInstituteofTechnology

Atlanta,Georgia30332-0280

1.INTRODUCTION(404)894-8450

ChikofskyandCross[7]definereverseengineeringas"theprocessofanalyzingasubjectsystem

m

itoidentifythesystem’scomponentsandtheirinterrelationshipsandcreaterepresentationsofthesyste

nanotherformoratahigherlevelofabstraction".Typically,thismeansconstructinganarchitectural

rdesignofasystemfromitssourcecode.Reverseengineeringcanbeusedforavarietyofpurposes:to

econstructorotherwiseimprovedocumentation;tofacilitatesoftwaremaintenanceorconversionactivi-

ties;ortoredesignandre-engineeranexistingsystem.

Thispaperdescribesamethodologyforreverseengineeringandhowitwasappliedtoanopera-

d

itionalsoftwaresystem.Themethodologymakesuseofapproachesandrepresentationstypicallyfoun

ntheforwardsoftwaredevelopmentprocess,includingahigh-level,textualoverviewandgraphical

d

Srepresentationsofdataflowsandfilestructures.Additionally,anewprogramanalysisprocedure,calle

ynchronizeRefinement,isusedtoextractdetailedimplementationinformation.

2.PROJECTDESCRIPTION

Thereverseengineeringprojectexaminedasystemtargetedforredesign,theInstallationMateriel

e

fConditionStatusReportingSystem(IMCSRS),aStandardArmyManagementInformationSystem.Th

unctionofIMCSRSistoassimilateanddistributeequipmentreadinessandmaintenancestatusinfor-

rmationtoU.S.Armyinstallationsanddivisions.Inessence,itisafilecreation,maintenance,and

eportingsystem.Itiscomposedofsixteenprogramsgroupedintosixexecutioncycles.Together,

d

sthesecomprisejustunder10,000linesofsourcecodewritteninCOBOL.Thesystemusesstandar

upportsoftwareforexecutiveprocesses,errordetectionandhandling,filespooling,andcommon

-

alibraryroutines.IMCSRSrunsonanIBM/370computerundertheOS/MVSoperatingsystem.Avail

bledocumentationconsistsoftheProgramMaintenanceManual,theFunctionalUser’sManual,and

theComputerOperationsManual.

Thereverseengineeringeffortispartofalargerprojectthathasagoaltoinvestigatetheapplica-

dbilityoftheAdaprogramminglanguageforsystemslikeIMCSRS.Thehigh-levelrepresentationpro-

ucedbyreverseengineeringwillserveasthebasisoftworedesignefforts,oneusingtraditionalFunc-

ttionalDecomposition[14],andtheotherusingObjectOrientedDesign[4].Iffeasible,twoimplementa-

ionswillbecompletedandtheresultscomparedforperformance,maintainability,anddevelopment

cost.

ThereverseengineeringwasconductedinaresearchlaboratoryattheGeorgiaInstituteofTech-

dnology.TheprimarycomputingvehicleusedwasaSUN386iworkstation,runningtheSUN(UNIX-

erivative)operatingsystemandtheSUNVIEWwindowingenvironment.Thestandardeditingtool(vi)

andsourcecontrolsystem(sccs)wereusedformanipulatingthesourcecode.Thecampusnetwork-2-

providedaccesstoamainframeCOBOLcompiler.

Asubstantialpartofthereverseengineeringeffortinvolvedtheproductionofgraphicalrepresen-

t

otationsofprogramstructures.Forthispurpose,theSoftwareThroughPicturesCASEtool[1],aproduc

ftheInteractiveDevelopmentEnvironmentsCorporation,wasused.

3.ISSUES

Partofthecharterforthereverseengineeringprojectwastodevelopasystematicmethodology

l

iforthereverseengineeringofprogramssimilartoIMCSRS.Becauseofthisspecificobjective,severa

ssuesarose.

1.Thereverseengineeringistargetedatredesign/conversionratherthanatotherpossiblegoals,

dsuchasimprovingmaintainability.Whatimplicationsdoesthishaveonthemethodology

eveloped?

2.IMCSRSwasthefirstsystemtobelookedatforconversion.Therewerenoavailabledata

e

oindicatingtheamountofeffortrequiredtoanalyzeanddescribeasystemofthissize.Onth

therhand,therewasaspecifictimeconstraint:thereverseengineeringhadtobecompleted

winfourcalendarmonths.Whatapproachshouldbetakentothereverseengineeringthat

ouldguaranteeusefulinformationattheendofthetimeperiod?

e3.IMCSRSisatypicaldataprocessingapplication.Whatimplicationdoesthishaveonth

methodology?

4.Theresultsofthereverseengineeringaretobeusedasastartingpointfortwoparallel

s

tredesignprojects.Whatformsshouldthehigh-levelrepresentationstakethatwouldnotbia

hecomparisoninfavorofoneortheotherofthedesignapproaches?

-5.IMCSRSisrelativelysmall,thecodeiscleanlystructured,anddocumentationisreadilyavail

able.Howmustthemethodologybeadaptedtodealwithmoredifficultsystems?

d

rTheapproachthatwaschosenwastop-downandusedavarietyofanalysismechanismsan

epresentations.Thefactthatitwastop-downassuredusofproducingsomeresults,evenifweranout

aoftimebeforecompletelyunderstandingallofthelow-levelimplementationdetails.Theapproachwas

lsomorelikelytogeneratearchitecturalinformationofuseduringredesign.Iftheprojectgoalshad

-

ustressedimprovingtheprogram’smaintainability,ratherthanfacilitatingredesign,thenamorebottom

papproachwouldhavebeenappropriate.Thisaddressedthefirsttwoissues.

s

aThefactthattheapproachtakenusedavarietyofanalysismechanismsandrepresentation

ddressedissues3and4,raisedabove.Amixedapproachhelpedtoavoidbiasingtheredesigneffort

-

candallowedustotakeadvantageofparticularrepresentationmechanismssuitableforthistypeofappli

ation.

ThelastissueisaddressedinSection6.2.

G

44.AMETHODOLOGYFORREVERSEENGINEERIN

.1.Background

Asystematicmethodologyprovidesavarietyofbenefitstosoftwareengineers.Mostimportantly,

pqualityisimproved.Becauseamethodologypreciselydescribestheintermediateandfinalresultsof

roduction,comparisonsarepossiblebetweentheproductsofindependentefforts,andplanningand

,

wschedulingeffortsarefacilitated.Also,becauseuniformproceduresareused,supporttoolscanbebuilt

hichalsocontributetoproductivityandqualityimprovements.Furthermore,uniformityallowstrain-

iingmaterialstobedevelopedsuchastutorialsandcourseware.Finally,amethodologysupports

nterimfeedback.Thiscantaketheformofbuilt-invalidationmechanismstodetectinconsistencyand