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VisualizationofPLCProgramsusingXMLM.BaniYounisandG.FreyJuniorprofessorshipAgentenbasedAutomationUniversityofKaiserslautemP.0.Box3049,D-67653Kaiserslautem,GermanyAbstract-DuetothegrowingcomplexityofPLCprogramsthereisanincreasinginterestintheapplicationofformalmethodsinthisarea.Formalmethodsallowrigidprovingofsystempropertiesinverificationandvalidation.OnewaytoapplyformalmethodsistoutilizeaformaldesignapproachinPLCprogramming.However,forexistingsoftwarethathastobeoptimized,changed,orportedtonewsystems.ThereistheneedforanapproachthatcanstartfromagivenPLCprogram.Therefore,formalizationofPLCprogramsisatopicofcurrentresearch.Thepaperoutlinesare-engineeringapproachbasedontheformalizationofPLCprograms.ThetransformationintoavendorindependentformatandthevisualizationofthestructureofPLCprogramsisidentifiedasanimportantintermediatestepinthisprocess.ItisshownhowXMLandcorrespondingtechnologiescanbeusedfortheformalizationandvisualizationofanexistingPLCprogram.I.INTRODUCTIONProgrammableLogicControllers(PLCs)areaspecialtypeofcomputersthatareusedinindustrialandsafetycriticalapplications.ThepurposeofaPLCistocontrolaparticularprocess,oracollectionofprocesses,byproducingelectricalcontrolsignalsinresponsetoelectricalprocess-relatedinputssignals.ThesystemscontrolledbyPLCsvarytremendously,withapplicationsinmanufacturing,chemicalprocesscontrol,machining,transportation,powerdistribution,andmanyotherfields.Automationapplicationscanrangeincomplexityfromasimplepaneltooperatethelightsandmotorizedwindowshadesinaconferenceroomtocompletelyautomatedmanufacturinglines.Withthewideningoftheirapplicationhorizon，PLCprogramsarebeingsubjecttoincreasedcomplexityandhighqualitydemandsespeciallyforsafety-criticalapplications.ThegrowingcomplexityoftheapplicationswithinthecomplianceoflimiteddevelopmenttimeaswellasthereusabilityofexistingsoftwareorPLCmodulesrequiresaformalapproachtobedeveloped[I].Ensuringthehighqualitydemandsrequiresverificationandvalidationproceduresaswellasanalysisandsimulationofexistingsystemstobecarriedout[2].OneoftheimportantfieldsfortheformalizationofPLCprogramsthathavebeengrowingupinrecenttimeisReverse-engineering[3].ReverseEngineeringisaprocessofevaluatingsomethingtounderstandhowitworksinordertoduplicateorenhanceit.WhilethereuseofPLCcodesisbeingestablishedasatoolforcombatingthecomplexityofPLCprograms,ReverseEngineeringissupposedtoreceiveincreasedimportanceinthecomingyearsespeciallyifexitinghardwarehastobereplacedbynewhardwarewithdifferentprogrammingenvironmentsVisualizationofexistingPLCprogramsisanimportantintermediatestepofReverseEngineering.ThepaperprovidesanapproachtowardsthevisualizationofPLCprogramsusingXMLwhichisanimportantapproachfortheorientationandbetterunderstandingforengineersworkingwithPLCprograms.Thepaperisstructuredasfollows.First,ashortintroductiontoPLCsandthecorrespondingprogrammingtechniquesaccordingtotheIEC61131-3standardisgiven.InSectionⅢanapproachforRe-engineeringbasedonformalizationofPLCprogramsisintroduced.ThetransformationofthePLCcodeintoavendorindependentformatisidentifiedasanimportantfirststepinthisprocess.XMLandcorrespondingtechnologiessuchasXSLandXSLTthatcanbeusedinthistransformationarepresentedinSectionIV.SectionVpresentstheapplicationofXMLforthevisualizationofPLCprogramsandillustratestheapproachwithanexample.ThefinalSectionsummarizestheresultsandgivesanoutlookon...