Architectuur H etN ieuw eInstituut - Collectie Het Nieuwe Instituut
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Architectuur Design Het Nieuwe Instituut Digitale Cultuur A preservation policy for the AutoCAD DWG / DXF file format author Henk Vanstappen ( DATABLE ) date 12 December 2019
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Transcript of Architectuur H etN ieuw eInstituut - Collectie Het Nieuwe Instituut
34
Architectuur
Design
HetNieuw
eInstituut
DigitaleCultuur Apreservationpolicyfor
theAutoCADDWG/DXFfileformat
authorHenkVanstappen
(DATABLE)
date12December2019
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1. Introduction 3 2. AutodeskDWG/DXFfileformat 42.1. AutoCADmodel 4
2.1.1. Modelkernel 42.1.2. Externalreferences 42.1.3. Metadata 52.1.4. Versionsandcompatibility 6
2.2. DWGfileformat 62.2.1. Fileformatspecification 62.2.2. FileStructure 62.2.3. Identification 72.2.4. InternalvalidationofaCADformat 7
2.3. DXFfileformat 82.3.1. Filestructure 82.3.2. Identification 9
2.4. CADSoftwareforDWG/DXF 92.4.1. AutoCAD 92.4.2. AutoCADexportformats 102.4.3. ProprietaryapplicationsforDWG/DXF 122.4.4. OpensourceapplicationsforDWG/DXF 12
2.5. SoftwarelibrariesforDWG/DXF 122.5.1. RealDWG 122.5.2. DWGDirect 132.5.3. OpenSourcelibraries 13
2.6. DWG/DXFViewersandconverters 132.7. Preservationrisks 14
3. PreservationStrategiesforAutocadDWG/DXF 16
4. Conclusion:TowardsaDWGfileformatpolicy 184.1. Pre-ingest 18
4.1.1. Technologypreservation 184.1.2. Dealingwithxrefs 184.1.3. Normalizationscenario’s 194.1.4. Normalizationtooling 204.1.5. Normalizationvalidation 21
4.2. Ingest 204.2.1. Formatidentification 204.2.2. Formatvalidation 214.2.3. Metadataextraction 21
4.3. Preservationplanning 224.4. Access 22
4.4.1. CreateDIP’s 224.4.2. Emulation 23
4.5. Technologywatch 23
5. Resources 24
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at6. Addenda 276.1. AutoCADsoftwarehistory 276.2. Fileformathistory 296.3. DWGmagicnumbers 306.4. DWGandDXFfileformatspecificationsinPRONOM 31
ThisdocumentislicensedundertheAttribution-ShareAlike4.0Unported(CCBY-SA4.0)license.Copyrightmayapplyonthirdpartyimages.
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HetNieuweInstituutinRotterdamisaninstituteforarchitecture,designanddigitalculture.ItisthekeeperoftheStateownedCollectionofDutchArchitectureandCityPlanning.
HetNieuweInstituutaimstoacquire,select,preserveandmakeaccessiblearchivesinareasonedmannerwithinitscollectionpolicy,acquisitionpolicyandPreservationpolicy.In2019,HetNieuweInstituutstartedtestinganddevelopingadigitalarchivefacility.Thefirsttestsforsettingupafileformatpolicyalsotakeplacewithinthisframework.Ultimately,HetNieuweInstituutmusthaveastrategyforfunctionalpreservation(migration,emulation).Inthiscontext,choiceswillhavetobemadewithintheframeworkofthePreservationPolicywithregardtothepreservationofessentialcharacteristicsoftheinformationobjects.
PracticalexperienceandpreviousanalysisshowedthatAutoCADDrawing(DWG) isusedveryfrequentlywithinthearchitecturaldesignprocessandasanexchangeformatbetweendifferentCADapplications.Duetothefrequentuseandthehighheritagevalue,HetNieuweInstituutwantstodevelopapolicywithregardtothisformat.BasedontheacquiredknowledgeabouttheDWGfileformatandtheAutoCADsoftware,HetNieuweInstituutwantsto:
– haveastudycarriedoutintothesustainabilityrisksassociatedwithfilesin theDWGfileformat;
– haveananalysiscarriedoutwithregardtoconsequencesforthe preservationstrategythatHetNieuweInstituutdevelops;
– obtainconclusionsandadviceonamigrationstrategytobeestablished towardssustainablefileformatsforDWGfiles.
SustainabilityrisksofCADfilesingeneralhavealreadybeendescribedinpreviousstudies.Concreteguidelines(fileformatpolicies)thattakeintoaccounttherequirementsofthearchivingorganization-suchasdeterminingthesignificantpropertiesandtheconsequencesthishaswithregardtothemigrationstrategy,however,werelacking.
Thisstudyattemptstofulfilthisneedand–basedonresearchoftheDWG/DXFfileformat–givesanumberofcomponentsofafileformatpolicyfortheAutoCADfileformat,takingintoaccounttheglobalpreservationstrategyof HetNieuweInstituutandthepresentorexistinginfrastructuretobedeveloped.
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at2. AutodeskDWG/DXFfileformat 2.1. AutoCADmodel
TheAutoCADmodel,asitisdefinedinaDWGfileanditsdependencies,holdsallthesignificantpropertiesthatcanbeselectedforretentioninfunctionofthedesignatedcommunity.
2.1.1. Modelkernel
CADsoftwareuseshighlycomplexmathematicaltechniquestodefineandrenderthreedimensionalmodelsandtheirproperties.Examplesofthesetechniques areB-splineorNURBSequations,non-parametricequations,orcombinations ofboth.AsSmith(2009)putsit,CADfilesdonotdescribeashapeassuch,but givearecipeofhowtheshapeshouldbebuilt.ThewayinwhichtheCADsoftwarecandescribeashapeislargelydeterminedbythesoftwarekernelthatisused.Translating3Dmodelsintoaformatthatdependsonanotherkernelthereforerunsagreaterriskoferrors.AutoCADisbasedontheShapeManagerkernel,whichwasforkedfromtheACISkernelversion7in2001(Strong,2019).1 Strong(2019)thereforestatesasaruleofthumbthatconversionstoanotherformatarelesslikelytocauseerrorswhenthetargetformatisbasedonthesamekernel.Errors(orartifacts)thatcanoccurwhentransformingtoanotherkernelaresliveredges,zero-areafaces,duplicateverticesandsoon(illustration).
Sliverfacesafterconversion2 TheAutoCADkernelsupportsBreporborderrepresentation.Brepconcernstheboundarybetweenfixedandnon-fixedgeometry,wherethefixedgeometryisasetofinterconnectedsurfaces.Thisisamathematicallypreciserepresentationofgeometry.TheoppositeofBrepisreferredtoasVrep(visualrepresentation),whichoffersonlyanapproximationofgeometry.AutocADDWGalsosupportsVrep.3
2.1.2. Externalreferences
InAutoCADausercaninsertanydrawingfileasanexternalreferenceorxrefinthecurrentdrawing.Withxrefs,changesmadeinthereferenceddrawingarereflectedinthecurrentdrawing.Attachedxrefsarelinkedto,butnotactually
1OthercommonformatsareParasolid(e.g.MicroStation),SMLibofCGM.2Imagefromhttps://www.engineersrule.com/advanced-breakdown-features-solidworks-fillet-tool/3VrepformatsincludeObj,STL,3DXML,3DPDF,Collada(.dae)andPLY.
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atinsertedin,anotherdrawing.Anychangestoareferenceddrawingaredisplayedinthecurrentdrawingwhenitisopenedorreloaded.Adrawingfilecanbeattachedasanxreftomultipledrawingsatthesametime.Conversely,multipledrawingscanbeattachedasreferenceddrawingstoasingledrawing(AutodeskKnowledgeNetwork,2019).Inmanycases,adrawinginthe.DWGformatwill beaddedasareference.However,itisalsopossibletouseotherfileformats:
– Image:Imagessuchas:.BMP,.JPG,.PNG,.TIFF,etc. – DWF:theDesignWebFormat:.DWF,.DWFX. – DGN:theMicrostationfileformat. – PDF:theAdobePortableFormatdocumentformat. – PointCloud:.RCPand.RCSfiles. – CoordinationModel:.NWDand.NWCfilesfromNavisworks.
Xrefsareidentifiedwithabsoluteorrelativepaths.Anabsolutepathisafullyspecifiedhierarchyoffoldersthatlocatestheexternalreference.Anabsolutepathincludesthelocalharddriveletterorthenetworkserverdriveletter.Relativepathsarepartiallyspecifiedfolderpathsthatassumethecurrentdriveletterorthefolderofthehostdrawing.Thisisthemostflexibleoption,andenablesyou tomoveasetofdrawingsfromyourcurrentdrivetoadifferentdrivethatusesthesamefolderstructure.XrefscanbeembeddedinaDWGfileasseparatelayerswiththebindingfunction.ABlockisaseparatedrawinginsertedintothecurrentdrawingasacompleteentity.Changesmadetotheoriginalblockwillnot translatetocurrentdrawing.
2.1.3. Metadata
Metadata(alsocalledProductManufacturingInformationorPMI)referstodatasuchasGeometricdimensioningandtolerancing(GD&T),dimensions,andnoteswhichareattachedtothesolidmodel(Strong,2019).Dataextractionisthe abilitytoextractdatafromobjectsinyourdrawingormultipledrawings.AutoCADprovidesaDataExtractionWizardthatcontrolstheextractionofthatdata(illustration).
AutoCADdataextractionwizard
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Likemostsoftware,newversionsofAutoCADareregularlyreleased,whichalsosupportfunctionalities.Tosupportthesechanges,updatesofthecorrespondingfileformatarealsomadeonaregularbasis.SinceAutoCADversion2000,AutodeskchangesitsDWGfileformatafterthreeversions.However,from2013,AutodeskdecidedtokeepthesameDWGformat(AC1027)for5versions,untilAutoCAD2018(AC1032).
AutoCADisbackwardscompatible,meaningfilescreatedinanyreleasecanbeopenedandeditedinthesameoranylaterrelease.Thesoftwareisnotforwardcompatible,butAutoCADsupportstheconversiontoolderformatversions.
BinaryDXFfilescanbereadonlybyAutoCADRelease10ormorerecentversions.
2.2. DWGfileformat
DWGistheAutoCADfileformatandisusedinternallybyAutodeskinAutoCAD,Revit,Inventoretc.aswellasmanythirdpartyapplications(Sheikh,2019).TheDWGfileformathasevolvedwiththetimesinceitsformalintroductionin1982(CADAZZ,2014).AutodesklicensedtheDWGfileformat,whichwasdevelopedby MikeRiddlein1970,asthebasisforAutoCAD.In1994Autodeskintroduced3DsolidmodellingoptionssimultaneouslywiththeemergenceofWindowsNT,whichmadetheuseofpowerfulapplicationsmoreaccessible.
2.2.1. Fileformatspecification
TheofficialDWGspecificationisundisclosedandproprietary.TheOpenDesignAlliance(ODA,agroupingofanumberofAutodeskcompetitors)thereforedecidedtoreverseengineertheDWGfileformat(Day,2006).
TheOpenDesignSpecificationforDWGfilesservesAutoCAD’sundocumentedandproprietaryDWGfileformat.ThespecificationincludesDWGfileformatversions13uptoandincludingversion2013.Thespecificationisabletoreadandwrite.dwgfiles,buthassomelimitations.,e.g.thecontentofthe53bytessectionbeforethesecondheaderisyetunknown(OpenDesignAlliance,2018).
2.2.2. FileStructure
DWGfilesusuallyincludeinformationabouttheimagecoordinatesandanymetadataassociatedwithit.ThefilestructureofDWGfileformatissummarizedasfollows(Sheek,2019;OpenDesignAlliance,2018).
– Header:thefileheaderconsistsofDWGHeadervariables(including theformatandversionstatement)andinformationaboutCyclic RedundancyCheck(CRC)whichisusedfortheerrordetection.
– ClassDefinitions:informationsuchasclassmetadatasizeofclassdata area,classnumberandchecksums. – ImageData:themetadataforthissectiondependsonthespecific.dwgtype.
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dictionaryentries,etc.correspondingtotheexistinglistofobjects. – ObjectMap:locationofeachobjectinthefileisspecifiedinthissection
offile. – SecondHeader:aduplicateofthefileheadersectiontowardstheendof
theDWGfile.
2.2.3. Identification
AutoCADfilescanbeidentifiedbyitsextension(.dwgor.dxf).Amorereliableandspecificidentificationmethodisbasedonthefilesignatureormagicnumberlocatedintheheaderofthefile.Magicnumberscanbeusedtoidentifytheformat,aswellasthesoftwareversion.TheDWGandDXFfileformatshaveentriesintheNationalArchivesPRONOMregistry.4
FileopenedinHEXviewerwithvisiblemagicnumber
2.2.4. InternalvalidationofaCADformat
CRCisamechanismtocontroltheintegrityofbitstream(e.g.afile).CRC’sareaddedtotheheaderofaDWGfiletosupportasoftwarefunctionthatcontrolstheintegrityofdifferentsectionsofthefile.
WiththereleaseofAutoCADR14.01in1998,AutodeskaddedanotherfileverificationthroughafunctioncalledDWGCHECKthatembeddedanencryptedchecksumandproductcode,calledaWaterMarkbyAutodesk,intoDWGfilescreatedbytheprogram.Butasafilecreatedwithanothersoftwarelibrarymayverywellbevalid,thisfunctionisnotveryinformative.
In2006AutodeskmodifiedAutoCAD2007,toinclude‘TrustedDWGtechnology’toembedthetextstring“AutodeskDWG.ThisfileisaTrustedDWGlastsavedbyanAutodeskapplicationorAutodesklicensedapplication”intotheDWGfiles.ThepurposeofthiswastohelpAutodesksoftwareusersensurethatthesefileswerecreatedbyanAutodeskorRealDWGapplication,whichshouldhelpinreducingtheriskofincompatibilities(Sheikh,2019).
4http://www.nationalarchives.gov.uk/PRONOM/Default.aspx
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DXFwasoriginallyintroducedinDecember1982aspartofAutoCAD1.0,andwasintendedtoprovideanexactASCIIbasedrepresentationofthedataintheAutoCADnativeDWGfileformat.AsAutoCADhasbecomemorecomplex,certainobjecttypes,includingACISsolidsandregions,arenotsupported(AutoCADDXF,n.d.)AsallinformationisencodedinASCII,aDXFfileusuallyrequiresmorestoragespacethanaDWGfile.
ThespecificationoftheDXFfileformatisavailablefromAutodesk(Autodesk,2011).Thelatestavailableversiondatesfrom2011.
DXFfilescanbeeitherASCIIorbinaryformat.UnlikeASCIIDXFfiles,whichentailatrade-offbetweensizeandfloating-pointaccuracy,binaryDXFfilespreservetheaccuracyinthedrawingdatabase.BinaryDXFfilesarereported tobeabout25%morecompact.(Autodesk,2011).
2.3.1. Filestructure
Essentially,aDXFfileiscomposedofpairsofcodesandassociatedvalues.Thecodes,knownasgroupcodes,indicatethetypeofvaluethatfollows.Usingthesegroupcodeandvaluepairs,aDXFfileisorganizedintosectionscomposedofrecords,whicharecomposedofagroupcodeandadataitem.EachgroupcodeandvalueareontheirownlineintheDXFfile(Autodesk,2011).
ADXFfile(version2011)iscomposedofthefollowingsections:
– Headersection:containsgeneralinformationaboutthedrawing.Itconsists ofanAutoCADdatabaseversionnumberandanumberofsystemvariables. Eachparametercontainsavariablenameanditsassociatedvalue.
– Classessection:holdstheinformationforapplication-definedclasses, whoseinstancesappearintheBLOCKS,ENTITIES,andOBJECTS sectionsofthedatabase.Aclassdefinitionispermanentlyfixedinclass hierarchy.
– Tablessection:containsdefinitionsforthefollowingsymboltables:• APPID(applicationidentificationtable)• BLOCK_RECORD(blockreferencetable)• DIMSTYLE(dimensionstyletable)• LAYER(layertable)• LTYPE(linetypetable)• STYLE(textstyletable)• UCS(usercoordinatesystemtable)• VIEW(viewtable)• VPORT(viewportconfigurationtable)
– Blockssection:containsblockdefinitionanddrawingentitiesthatmakeup eachblockreferenceinthedrawing.
– Entitiessection:containsthegraphicalobjects(entities)inthedrawing, includingblockreferences(insertentities).
– Objectssection:containsthenongraphicalobjectsinthedrawing.Objects aresimilartoentities,exceptthattheyhavenographicalorgeometric
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– Thumbnailimagesection:containsthepreviewimagedataforthedrawing. Thissectionisoptional.
2.3.2. Identification
TheidentificationoftheASCIIDXFfileformatandversionisdocumentedinthe$ACADVERvariableintheheadersection(Autodesk2011):
– AC1006=R10; – AC1009=R11andR12; – AC1012=R13; – AC1014=R14; – AC1015=AutoCAD2000; – AC1018=AutoCAD2004; – AC1021=AutoCAD2007; – AC1024=AutoCAD2010
AbinaryDXFfilebeginswitha22-bytesentinelconsistingofthefollowingstring:AutoCADBinaryDXF
2.4. CADSoftwareforDWG/DXF
2.4.1. AutoCAD
AutoCADisacommercialcomputer-aideddesign(CAD)anddraftingsoftwareapplication.DevelopedandmarketedbyAutodesk,AutoCADwasfirstreleased inDecember1989asadesktopapplication.
AutoCADisavailableintwoversions:thefullfledgedAutoCADandAutoCADLT.Thelatterdoesnotsupport3D.AutoCADisavailableinanumberofvariants(akatoolsetsorverticals):AutoCADArchitecture,AutoCADElectrical,AutoCADMap3D,AutoCADMechanical,AutoCADMEP,AutoCADPlant3DenAutoCADRasterDesign.
Autodeskofferstwotypesofaccess,single-userandmulti-user,withtheirownassociatedlicensetype.Userswithstand-alonelicensesmustconnecttotheinternetevery30daystovalidatetheirAutodeskID,butwiththeexceptionofcloud-basedservices,thesoftwareworksofflineforupto30days.
Thelicenseagreementallowstheusertomakeonearchivalcopyofthesolelyforbackupandarchivalpurposesandsolelyforthedurationofasubscription.Thestructureandorganization,theunderlyingalgorithmsandotherinternals, theprotocols,datastructuresandotherexternals,andthesourcecodeoftheOfferingsandtheAPIsconstituteproprietaryandconfidentialinformationofAutodesk.Ausermustagreenottoengageinanydecompiling,disassemblingorotherreverseengineeringorotherwiseattemptingtodiscover,learnorstudythestructureororganization,underlyingalgorithmsorotherinternals,theprotocols,datastructuresorotherexternals,orthesourcecodeoftheapplication.
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Format
3DDWF(*.dwf)3DDWFx(*.dwfx)
ACIS(*.sat) DXXExtract(*.dxx)
EncapsulatedPS(*.eps) IFC(*.ifc)
IGES(*.iges;*.igs)
Description
AutodeskDesignWebFormat
ACISsolidobject
AttributeextractDXF™ EncapsulatedPostScript IndustryFoundationClasses
IGES
Notes
3DDWFisacompressed,proprietaryfileformatforviewingandinspectingCADfiles. ExportstrimmedNURBSsurfaces,regions,and3DsolidstoanACISfileinASCII(SAT)format.Otherobjects,suchas linesandarcs,areignored. Extractsattributeinformationfromadrawingandcreatesaseparatetextfileforusewithdatabasesoftware. ExportofafileinPostScriptformatasanEPSfile,handlessomeobjectsspecially,e.g.a2D(planar)polylinewithuniformwidthisoutputasaPostScriptstrokedpath.ThePostScriptendcapandmiterlimitvariablesaresettoapproximatethesegmentjoining. ThecoreAutoCADprogramisnotabletoexporttothisfileformat.AutoCADArchitecture,AutoCADMEPorAutodeskCivil3DhaveanIFCExportfeaturebuiltin. Underidealconditions,translationpreservestheappearanceandfunctionalityofentities.
2.4.2. AutoCADexportformats
AutoCADnativelysupportsthefollowingexportformats:
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Lithography(*.stl) STEP
V7DGN(*.dgn)
V8DGN(*.dgn)
IGES
Solidobjectstereolithography
/
MicroStationDGN
MicroStationDGN
However,thisprocesshaslimitations,andsomedatawillnotbepreservedinaroundtriptoIGESandback.Forexample,whenexportingtoIGES,a2DpolylineistranslatedasIGESentity106:12.WhenimportingfromIGES,entity106:12translatestoaspline.Hence,theresultingdrawingmaynotbeidenticaltotheoriginaldrawing.
The3DsoliddataistranslatedtoafacetedmeshrepresentationconsistingofasetoftrianglesandsavedtoanSTLfile. ThecoreAutoCADprogramisnotabletoexporttothisfileformat.AutoCADMechanicaltoolsetexportstoSTEPversionsAP214andAP203E2 TheexportprocesstranslatesbasicDWGfiledataintothecorrespondingDGNfiledata,andspecializeddataasabestfit.Thereareseveraltranslationoptionstodeterminehowdataistranslatedduringtheexportprocess. Seeabove
Notes: – AutoCADalsosupportstheexportofrasterimagefileformats(TIFF,
PNG,JPEG,BMP)andPDF. – ExporttoACIS,DXX,IGESandSTLisnotsupportedinAutoCADLT. – Exporttootherformatsmaybeavailablethroughthirdpartycomponents,
availableintheAutodeskAppStore.
5https://apps.autodesk.com/ACD/en/List/Search?facet=__category%3a%3aTranslator
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Thereisamultitudeofapplicationsthatsupportimporting,editingandexportingofDWG/DXFformat.SomeofthemarebasedontheAutodesksoftwarelibrary,whileothersusetheODAlibraryoranopensourcevariant.Itisoftenunclearwhichengineisused.Belowwelistafew:
– ABViewerbyCadsoftttools – AlibreDesignbyAlibre,LLC – AllyCADbyKnowledgeBase – ArchiCADbyGraphisoft – BricsCADbyBricsys – IntelliCADbyIntelliCADTechnologyConsortium – MicroStationbyBentleySystems – AutodeskRevit – Rhinoceros3DbyRobertMcNeelandAssociates – SketchUpbyTrimble – SolidWorksbySolidWorksCorp. – SolidEdgebySiemensPLMSoftware
2.4.4. OpensourceapplicationsforDWG/DXF
FreeCADisafreeandopen-sourceapplicationthatcanworkwiththeDXF.FreeCAD’ssupportfortheDWGfileformathasbeenproblematicduetosoftwarelicensecompatibilityproblemswiththeGNULibreDWGlibrary(FreeCAD,n.d.)LibreCADisafreeandopen-source(GPLv2)2DCADapplicationthatcanopenDWGandDXFfiles.LibreCADusesthelibdxfrwsoftwarelibrary.6
2.5. SoftwarelibrariesforDWG/DXF
Asoftwarelibraryisasuiteofdataandprogrammingcodethatisusedtodevelopsoftwareprogramsandapplications.Itisdesignedtoassistboththeprogrammerandtheprogramminglanguagecompilerinbuildingandexecutingsoftware.7AutoDeskaswellasit’scompetitorshavedevelopedsoftware librariesthatcanread,processandexportDWGandDXFfiles.
2.5.1. RealDWG
TheRealDWGdevelopertoolkitisasoftwarelibrarythatallowsC++and.NETdeveloperstoreadandwriteAutoCADsoftwareDWGandDXFfiles.RealDWGcontainstheAPIsforreadingandwritingAutoCADDWGandDXFfiles.RealDWGdoesnotcontainsupportforviewingandaccesstotheAutoCADuserinterface.RealDWGisusedtocreatehostapplicationsanddoesnotrequirethepresenceofAutoCADsoftware.
ThemostcurrentversionofRealDWGprovidescompatibilitywithAutoCADDWGfiles,includingreadandwritesupportforAutoCADreleasessinceAutoCADRelease14anddrawingenhancementsavailablewiththemostcurrentversionofAutoCAD. 6https://wiki.librecad.org/7https://www.techopedia.com/definition/3828/software-library
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TheOpenDesignAlliance’sDrawingsSDKisadevelopmenttoolkitthatprovidesaccesstoalldatainDWGthroughanobject-orientedAPI,allowscreatingand editingofaDWGfile.ThelibraryisusedinproductssuchasBricsysandIntellicad.8
2.5.3. OpenSourcelibraries
TheopensourcecommunityhasmadeseveraleffortstoprovideatrulyopensoftwarelibrarythatcanhandleDWGfiles:
– GNULibreDWG(forkedinlate2009fromlibDWG)canreadmost(!)parts ofDWGfilesfromversionR13upto2004.ButasthelibreDWGlibrary isreleasedundertheGNUGPLv3itcan’tbeusedbymosttargetedopen sourcesoftware,likeFreeCAD,LibreCADandBlender,duetoaGPLv2/ GPLv3licenseincompatibility.Theprojecthasstalledsince2011.9
– LibDWG-freeaccesstoDWGprojectwasreactivatedinseptember2013. Itwasre-forkedfromLibreDWG.However,sincemarch2015noupdate wasreleasedanditgotabandonedagain.10
– AGPLv2licensedalternativeisthelibdxfrwproject,whichcanreadsimple 2DDWGfiles.11
2.6. DWG/DXFViewersandconverters
BothAutodeskandODAhavemadeviewersavailablethatcanbedownloadedforfree.Webbasedviewersareavailableaswell,e.g.AutodeskViewer.12
– AutodeskDWGTrueview13isafreewarestand-aloneDWGviewerwith DWGTrueConvertsoftwareincluded,builtonthesameviewingengineas AutoCADsoftwareandcapableofviewingandconvertingbetween differentDWGandDXFversions.
– AutodeskDesignReview14softwareaddsapossibilitytoopenDWGfiles inDesignReviewtotakeadvantageofmeasureandmarkupcapabilities, sheetsetorganization,andstatustracking.
– ODADrawingsExplorer15isafreewarestandaloneviewerforDWGfiles.It isintendedforrenderingandtestingandrunsonWindows,Linux,macOS.
– ODAFileConverterapplicationhasagraphicalinterfaceandacommand- lineinterface,whichiscapableofbatchconvertingbetweendifferent versionsofDWGandDXF.16Iftheauditflagisenabled,anaudit/repair operationwillbeappliedtoeachfileasitisloaded.ItrunsonWindows, LinuxandmacOS.
8https://www.opendesign.com/products/drawings 9https://www.gnu.org/software/libredwg/10https://libdwg.sourceforge.io/en/index.html11https://github.com/LibreCAD/libdxfrw12https://viewer.autodesk.com/13https://www.autodesk.com/products/dwg14https://www.autodesk.com/products/design-review/overview15https://www.opendesign.com/guestfiles/oda_drawings_explorer16https://www.opendesign.com/guestfiles/oda_file_converter
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Thesustainabilityofafileformathasbeendefinedbydifferentauthors,withtheobjectiveoftheselectionofarchivalformats,i.e.fileformatsthatcanbeacceptedinadigitalpreservationsystem(Rog&vanWijk,2008;Todd,2009;Folk&Barkstrom,2003).
BasedontheanalysisoftheAutoCADsoftwareandtheDWGfileformat,itispossibletoidentifythepreservationrisksrelatedtoafileformat.Todeterminetheserisksweusealistofcriteriatodeterminewhetheraformatissuitable asanarchiveformat:
– Adoption:theextenttowhichtheformatisinwidespreaduse,e.g;the availabilityofsoftwareorsoftwarelibraries;
– Platformindependence:theextenttowhichtheformatisindependentof specificsupportfromhardwareandsoftware;
– Disclosure:theextenttowhichthefileformatspecificationisinthepublic domain;
– Transparency:thereadinesswithwhichthefileformatcanbeinspected orinterrogatedtodiscoveritsidentityandattributes,asagainstwhereitis obscuredbycompression,‘wrapper’dataarchitecturesorothertechniques;
– Metadatasupport:theextenttowhichdescriptiveinformationis supportedinmachinereadableformwithintheformat.ThisincludesOAIS representationinformationandoccasionallyhowfarthefileformatsupports therecordingofmanagementprocessesithasbeensubjectto.
AdoptionofAutoCADishigh:theAutoCADsoftwareandDWGfileformatisusedbyarchitectsanddesignersallovertheworld.Enlyft(2019)reportsacurrentmarketshareforAutodeskAutoCADof37%.Thereisaglobalcommunityofengineers,architectsanddesigners,supportedbyarangeofserviceprovidersthatprovideeducationandsupportaswellaspluginsandextensionsonthesoftware.
DWGisalsosupportedinotherCADapplications,eitherasanativeformatorasaformatthatcanbeimportedand/orexported.
ThefileformatitselfisplatformindependentinthatallDWGorDXFfilescanbereadbytheWindowsandmacOSversionsoftheAutoCADsoftware(Linuxisnotsupported).Userswithstand-alonelicensesmustconnecttotheinternetevery30daystovalidatetheirAutodeskID,whichmeansthereisalsoandependencyofAutodesk’susermanagementservice.
InternallytheAutoCADapplicationdependsonfewothertechnologies,exceptwhenfilesindifferentfileformatsareembeddedusingxrefs.AsanalternativetoAutoCAD,applicationsandsoftwarelibrariesareavailablefromthirdparties,albeitwithsomelimitationsregardingthesupportofDWGentities.
AstheofficialDWGfileformatspecificationisnotpublishedoravailableotherwise,disclosureisapreservationrisk.ThankstotheeffortsoftheOpenDesignAlliance,aspecificationisavailablethatcloselyapproximatestheoriginal.
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ThespecificationoftheDXFcounterpartispublishedbyAutodesk,butthisversiondatesbackto2011andthusisnotcompatiblewithmostrecentversionsofDWG.ConversionfromDWGtoDXFthereforehasariskofinformationloss.
Also,thesourcecodeoftheapplicationitselfisundisclosed.Thereverseengineeringeffortshaveresultedinunofficialbutgenerallyspeakingcompletealternativesintheformofafileformatspecificationandacompeting(proprietary)SDKthatcanhandleDWGandDXFfiles.Theinitiativestoprovideatrulyopensourcesoftwarelibraryorapplicationhavenotbeensuccessfulsofar.
ADWGfilecanbeidentifiedbasedontheextension.dwgor(evenbetter)byananalysisofthefileheader,whichwillalsorevealthesoftwareversionitwasproducedwith.Asthestructureofthefileisdocumentedbutsasthefileisbinary,filecontentscannotbeevaluatedwithoutdedicatedsoftware.Inthisrespect,ASCIIDXFfilesaremoretransparent,butaswehaveseentheASCIIfilesdon’tsupportallinformationentitiesinaDWGfile.
Metadataextraction(exceptforthefileformatversion,whichcanbeextractedwithtoolssuchasDROIDorSiegfried)ispossiblewithdedicatedsoftwareonly.
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Strategiesandapproachessuchasnormalizationtoanarchivalfileformathavesuccessfullybeenimplementedforrelativelysimplefiletypessuchas3Drasterimages(e.g.TIFF)ortext(ODT,XML).Becauseofitsinherentcomplexitywhenpreserving3Dfiles,oneisconfrontedwithamuchhighercomplexity,stemmingfrombothinterdependenciesonothersystemsandtranslatorsandcomplexinterrelationshipsbetweenpartsofasinglemodel,e.g.geometry,differencesintolerances,supportedentitiesormetadata,etc.(Chinn,2009).Asattentiontotheproblemofpreserving3DCADfilesgrew,variousstudiesandprojectswereconductedthatformulatedadviceonthesustainabilityof3DCADfileformatsandpreservationstrategies.
TheArchaeologyDataService(ADS)preservesarchaeologicaldatasetswithintheareabroadlydefinedasArchaeologyandtheHistoricEnvironment.Everyfileispreservedinastandardised(‘normalized’)format.Thechoiceofarchivalformatsisbasedonamixtureoftechnicalconsiderations,judgementsonlongevityofformatandeaseofestablishingfuturemigrations.ADShadtraditionallyusedDXF(R14)inAIPandDIPsupportfortextualencoding(ASCII)anditsprimarypurposeasanexchangeformatwhichcouldbeusedbeyondAutodesksoftware.DuetothefastdevelopmentoftheAutoCADsoftware,theDXFformathasseenalmostasmanyversionupdatesastheproprietaryDWGformat.Asaresult,thedecisionwasmadeinearly2014tochangetheADSarchivingpolicyandadoptDWGversion2010(AC1024)(Evans,2016;Green2016).
Source:ArchaeologyDataService
Ball(2013)recommendsthatarchives“normalizeCADmodelstoatleastone,butideallytwoorthree,vendor-neutralstandardformats,”particularlythosedefinedbytheSTEP(StandardfortheExchangeofProductModelData)internationalstandard(ISO10303).
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ThefirstFACADEproject(FACADE,2013)recommendsthatfourversionsofCADfilesbekeptforpreservation:
– theoriginal; – adisseminationformat,suchas3DPDF – a‘heavyweight’standardformat,suchasIFCorSTEP – a‘lightweight’format,suchasIGES,whichretainsthesimplegeometryof
themodel.
TheDURAARKprojectstudiedhethesustainabilityoftheISOstandardizedIFC(IndustryFoundationClasses)fileformatforBIMs,whichwasconsideredwellsuitedforarchivalpurposesfromasustainabilitypointofview(Lindlar&Saemann,2014).
Lowet(2016)proposestosavetheoriginal(2D)DWGfilesandtocountonthebackwardcompatibilityoftheDWGforthetimebeing.Atthesametime,atechnologywatchmustbesetuptosignalanyincreasedrisks(nolongersupportingolderversionsofDWG).Inthemeantime,thenormalizationofDWGfilescanalreadybeprepared.Inthisscenario,DXFischosenasthearchivalformat.
Finally,intheirrepresentationofmanagingandprovidingarchitecturearchivesattheCanadianCentreforArchitecture(CCA),Stewart&Breitweiser(2019)seemtosuggestthatnostandardizationormigrationisbeingperformedonDWGandDXFfiles.
17http://www.lotar-international.org
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InthefollowingchapterweproposeaprocedureforthehandlingofAutoCADDWGandDXFfilesinatrusteddigitalarchive.ThestepsofthisprocedurearelooselybasedontheOAISmodel,asexplainedin(Walsh,2015).Thestepsassumeanalreadydefinedstrategyandoverallprocedureformanagementandpreservationofdigitalarchives,asdefinedinRas,2018.ItalsoassumesthattheorganizationhasanOAIScompliantmanagementsystem,i.c.Archivematica.18Vitalcomponentsofadigitalarchiveinfrastructure(suchasstoragemediaandrepositorysystems)arethereforementionedonlybriefly.WehighlightthosepartsthatarespecifictoDWG/DXFfiles.
HetNieuweInstituutdoestherecording,management,preservationactionsandtheaccessibilityactionsofdigitalobjectsasmuchaspossibleautomatically.Thisisfeasiblewithregardtobitpreservation.Thedegreeofautomationwilldecreaseforresearchandfunctionalpreservation.Thisgenerallyrequirescustomization.
AlthougharchitecturalarchiveswithCADfilescandiffergreatlyandrequiredifferentlevelsofcareandanalysisinpractice,wetrytodescribeagenericprocesshere,towhichexceptionscanbeimposeddependingonspecificrequirements.
4.1. Pre-ingest
InthePre-ingestphaseHetNieuweInstituutcarriesoutcheckson:
– Thetechnicalformatsoftheinformationobjectssupplied; – Thelimitationsindigitalsignatures,compressionandothertechnical
operations; – Thepresenceofmetadata; – Theagreementswithregardto(re)useandaccess(Ras,2018).
4.1.1. Technologypreservation
Preservingtechnologyapproachesattempttokeepdatainspecificlogicalorphysicalformatsandusetechnologyoriginallyassociatedwiththoseformats.Thiscanbeachievedbyactuallypreservingtheentireenvironment(hardware,operatingsystem,software,files)torepresenttheoriginalDWG/DXFmodelsinanarchivalcontext(Vanstappen,2019).This‘computermuseum’approachisnotbeconsideredasaviablepreservationstrategy.However,itisagoodideatoarchivesoftwarewithaviewtodocumentingthefunctionalitiesoftheapplicationandasameanstoperformpre-ingestedandingestedprocessesinsofarasthesecannotbeembeddedwithintheArchivematicaworkflows.
4.1.2. Dealingwithxrefs
Inthepre-ingestphase,filesmaybetakenoutoftheiroriginalenvironment.Whendoingso,precautionsmustbetakentoavoidfilecorruptionthroughthe
18https://www.archivematica.org/
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4.1.3. Normalizationscenario’s
Atthemoment,HetNieuweInstituutdoesnotimposeanyrestrictionsonthenumberortypeoffileformatstobeincluded.Thereisnolegalframeworkforthis.HetNieuweInstituutwill,however,drawupalistofpreferredformats.AccordingtoHetNieuweInstituut’spreservationpolicy,aconversionfromcertainformatstoamoresustainableformatmayalreadyfollow.Bothformats–includingthemetadata–aresaved.Attheendofthepre-ingestthereisavalidandusablesubmissioninformationpackage(SIP).
Asdescribedintheoverviewofexistingandrecommendedpreservationstrategies,severalscenarioswithregardtonormalizationareconceivable:
– Nonormalization:DWGandDXFfilesaresavedwithoutfurther intervention.AlthoughDWGdoesnotstrictlymeettherequirementsof anarchivingformat,thisoptioniscertainlyacceptable.Initscurrent formandcontext,DWGhasfewimmediatepreservationrisks.Thechance thattheformatturnsouttobeillegibleintheshortormediumtermisvery limited.ThesameappliestoDXF,whichmoreoverscoresbetterintermsof transparencyandisitselfanopenstandard.
– WhenthepreservationpolicyrequiresthenormalizationofDWGtoan openandstandardizedarchivingformat,thereareseveraloptions:
• ThesometimesproposedstrategytoconvertDWGtoASCIIDXFfiles involvesanumberofrisks.AlthoughDXFisanopenspecificationand ismoretransparentduetoitsASCIIcoding,thecurrentspecification isconsiderablybehindthelatestDWGspecification.Moreover,the accuracyofASCIIDXFislower.Lossofinformationisthereforeareal risk.ConversiontoDXFisonlyrecommendedasansupplementary step,butnormalizationtoanotherformatispreferred.• STEPAP203definesthegeometry,topology,andconfiguration managementdataofsolidmodelsformechanicalpartsandassemblies. ThisfiletypedoesnotmanageColorsandLayers.AP214haseverything aAP203fileincludes,butaddscolors,layers,geometricdimensioningand tolerance,anddesignintent.AP214isconsideredanextensionofAP203.• IFC(IndustryFoundationClasses)isanopenfileformatforthe descriptionofarchitectural,buildingandconstructionindustrydata. TheformatisusedasthecollaborationformatinBuildinginformation modeling(BIM)projects.
Inthepresentcircumstances,however,weestimatethenecessityorpriorityofnormalizationtobelow.OnlyifsupportfromDWGappearstobeuncertaintyinthefuture(cf.technologywatch),thisnormalizationstepisrecommended.TakingintoaccountthebackwardscompatibilityofDWG,thereiscurrentlynoneedforamigrationtoamorerecentformatofDWG.
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NormalizationisArchivematica’sprimaryformatpreservationstrategy.ThepreservationcopiesareaddedtotheAIPandtheaccesscopiesareusedtogenerateaDIPforuploadtotheaccesssystem.SeveraldifferenttoolsareusedtocompletenormalizationtaskswithinArchivematica,dependingontheformatofthefile.NoneofthebuiltinoptionsarecapableofconvertingDWG/DXFfiles.Ifnormalizationisrequired,somealternativeoptionsareavailabletoincludethisstep–eventuallyintoArchivematica’sautomatedworkflow:
– TheODAFileConverterapplicationiscapableofDWG/DXFconversion andversionmigrationfromthecommandline.
– DWGTrueViewisalsocapableofexecutingthesamecommands,fromthe (Windows)commandline.
– Specializedtools,suchasTransMagic19shouldbeinvestigatedfor normalizationtootherformats.
4.1.5. Normalizationvalidation
Validationoftheresultofanormalizationprocessimpliesthateveryfeatureoftheoriginalfileformat(geometry,position,metadata,…)ischeckedagainstthefeaturesofthemigratedfile.Thisprocessprovestobeverycomplex,evenforarelativelysimpleformatasSTEP(Cinn,2009).Strong(2018)distinguishesthreewaysofcomparingtwomodels:
– Visualinspection,inwhichtheoriginaliscoloredgreenandtherevised versioniscoloredred.Bothmodelsareswitchedtowireframedisplayand visuallyinspectedusingbrute-forceeyeballstrength.
– ComparisonsoftwarebuiltintoaCADapplication,whenavailable.Itis reportedtoberudimentaryandtolacktheprecision.
– UseofCADComparisonsoftwarethatautomaticallyevaluatestheexact degreetowhichtwomodelshavethesamegeometry,providesamethod toauthenticatethatthetwomodelsarethesameforallpracticalpurposes anddetermineshowwellagroupingofpointsfitstoanexisting3DCAD model.
4.2. Ingest
InHetNieuweInstituut’spreservationpolicy,attheingestoftheSIPanumberofchecksandidentificationstakeplace(Ras,2018).
4.2.1. Formatidentification
Identificationistheprocessofanalyzinggiveninformationaboutafiletoderiveitsformat.InArchivematica,therearethreefileidentificationtoolssupportingtwoidentificationmethods:
– Fileextension,asimplescriptwhichidentifiesfilesbytheirfileextension andthusisnotcapableofdistinguishingdifferentformatversions;
19https://transmagic.com/cad-automation/
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connectthistoaPRONOMID.
ThePRONOMdatabasecontainsthesignaturesofthedifferentDWGandDXFversions.Archivalsoftwareisthereforesufficientlyequippedtoadequatelyrecognizetheformatsandversions.However,themostrecentversionsofDWGarenotyetincludedinthedatabase(themostrecentisDWG2014,cf.Addenda).HetNieuweInstituutshouldtaketheinitiativeheretoaddthesesignaturestothePRONOMdatabase.
4.2.2. Formatvalidation
Formatvalidationensuresthatfilesarewell-formedandcompliantwithanyrelevantformatspecifications.Therearetwoaspectsonthevalidationprocess.Firstlyavalidationcanbeappliedtoafileinordertocontrolifitisstructuredconformingthefileformatspecification.ThedigitalpreservationcommunityhasproducedestablishedtoolssuchasJHOVEandVeraPDFtovalidatefileformatssuchasWAV,TIFForPDF.22,23ForDWGfiles,validationcanbeexecutedwith proprietaryvalidatorsfromsoftwareproducers.Archivematicacontainstwovalidationtools:JHOVEandMediaConch,bothofwhicharenotsuitableforvalidatingDWGorDXFfiles.Alimitedvalidationcanbeexecutedwiththenormalizationtoolsthatarepreviouslymentioned.Asmentionedbefore,AutoCADactuallyprovidesan(overlystrict)validationfunctionalitycalledDWGCHECK.
4.2.3. Metadataextraction
Metadataisinformationaboutrelationshipsbetweenandinformationaboutinformationobjects.HetNieuweInstituutisworkingonaMetadataDirective. Thisspecifieswhichmetadatamustbestored,withinwhichsystemsandwithwhichmutualrelationships(Ras,2018).
Adistinctionismadebetween:
– Descriptivemetadata.Thesedescribetheinformationobjectsoncontent characteristics;
– Technicalmetadata.Thesedescribetheinformationobjectsthemselves andarenecessarytoguaranteelong-termaccess[Characterization];
– Structuralmetadata.Thesedescribethestructureofthearchivesand mutualrelationshipswithinanarchive.
Characterizationistheprocessofproducingtechnicalmetadataforanobject.Archivematica’scharacterizationaimsbothtodocumenttheobject’ssignificantpropertiesandtoextracttechnicalmetadatacontainedwithintheobject.Archivematicahasfourcharacterizationtoolsavailableuponinstallation.Unfortunately,againnoneofthesetoolssupportsmetadataextractionfrom DWGorDXFfiles.24
20https://github.com/openpreserve/fido/ 21https://www.itforarchivists.com/siegfried22https://jhove.openpreservation.org23https://verapdf.org24https://www.archivematica.org/en/docs/archivematica-1.10/user-manual/preservation-planning/
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4.3. Preservationplanning
Thee-DepotofHetNieuweInstituutwillbesetupforbothbitpreservationandfunctionalpreservation(Ras,2018).Thisisdoneby:
– Maintainingoneoriginalandatleastonecopyofeachbitstream; – Guaranteebitstreamintegrity(checkchecksum)andsetupacheckcycle; – Beingabletoproveanddocumentthis.
Acontrolmechanismtochecktheintegrityoffilescanbebasedonacryptographicalgorithm(checkum)andshouldbeinplaceatingestandrunatregularintervalstotraceanyunwantedchangeofafile(bitrot).Thebuilt-in checksummechanismofDWGdoesnotreplacetheneedforthiscontrolmechanism:
– Theinternalmechanismisonlyexecutedwhenthefileisactuallyopened withanapplicationthatsupportsthismechanism.
– Theintegritycheckmustbeexecutedonallmanifestationsofthedocument (originalfile,metadataand–whenapplicable–thenormalizedfile).
4.4. Access
HetNieuweInstituut’sPreservationpolicystatesthattheaccessfunctionalitysupportstheaccessible,readableandusableofferingofinformationobjects.Dependingonthedesignatedcommunityoruser,theinformationcanbemadeavailableinvariousways,forexampleviaaviewerordownloadfunctionality(Ras,2018).
4.4.1. CreateDIP’s
WhengrantingaccesstotheDWG/DXFfiles,theusermustbeabletovisualizeandstudythem.Thewayinwhichthisisfacilitateddependsontherequirementsoftheuserandistailoredtothedesignatedcommunity.
AccessthereforeassumesthecreationofaDIP,inwhichthefileispresentedinaformthatmayormaynothavebeenmodified.Differentoptionsareapplicablehere:
– Creationofaaccesscopyinacommonfileformat,suchasPDForJPEG. – Representingtheoriginalformatinasuitableviewer(e.g.AutodeskDWG
TruevieworODADrawingsExplorer). – Representingthenormalizedformatinasuitableviewer(e.g.Autodesk
Viewer 26).
25https://knowledge.autodesk.com/guidref/MAP/2019/learn-explore/GUID-A5F25740-7E04-402E-A5AB-
C1177FD8F43826https://viewer.autodesk.com
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TheuseofPDFnaturallyhascertainlimitationsontheaccuraterepresentation ofaCADfile–inparticularof3Dfiles.Ontheotherhand,itisanaccessibleformatthatisalreadypresentonmostdesktops.Theuseofarasterimage(e.g.JPG)offersanevengreateraccessibility,butthedegreeofinformationlossisevenhigher.PDFandJPGaccessfilesarethereforeespeciallysuitableforgivingafirstimpressionofthefile.Specializedtoolsareneededtocreatesuchaccessformats(seeaboveunderNormalisation).
4.4.2. Emulation
Analternativetoofferingaccessfilesororiginalfilesinaviewerorasadownloadistoemulatetheentireenvironment(i.e.operatingsystemandsoftware).Thisapproachofferstheadvantagethattheinformationobjectcanbedisplayedinitsoriginalcontextoranapproximationthereof.Moreover,thisapproachdoesnotdependontheavailabilityofviewers.Ontheotherhand,settingupanemulationenvironmentprovidesadditionalcomplexity.
Theemulationoptionthereforedoesnotseemtobeapriorityforthenearfuture.Inthelongertermoperatingsystemsandsoftwaremaybecomeobsolete. Thereforeemulationisastrategythatneedsfurtherinvestigation.Thisinvestigationinvolvesnotonlythetechnicalchallenges,butalsothelegalbarrierscausedbycopyrightissuesonsoftwareandoperatingsystems.
4.5. Technologywatch
DuetotheevolutionofCADsoftware,itisimportanttocloselyfollowtechnologicaltrends.ThisTechnologywatchfunctionincludes:
– evolutionoftheDWG/DXFfileformat,inparticularthebackward compatibilityoftheformatandthecompatibilitywitharchivingstandards suchasSTEPandIFC;
– followingupondevelopmentsinsoftwaredevelopmentwithregardtoCAD applicationsandviewers;
– followingtrendsinacceptanceandmarketshareoftheDWG/DXFformat; – followinguponinnovationsinemulationofobsoletesoftwareandoperating
systems; – monitortheavailabilityoffilesignaturesofnewversionsofDWGandDXF
inexternaldatabases(e.g.PRONOM),andpossiblytakeactiontoadd thesesignatures.
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at5. Resources
AutoCADDXF(n.d.).InWikipedia.(Retrievedfromhttps://en.wikipedia.org/wiki/AutoCAD_DXF.) AutodeskKnowledgeNetwork(2019).AboutAttachingandDetachingReferencedDrawings(Xrefs).(Retrievedfromhttps://knowledge.autodesk.com/support/autocad/getting-started/caas/CloudHelp/cloudhelp/2016/ENU/AutoCAD-Core/files/GUID-A987D2FF-45BD-474E-99C1-E6316A42F667-htm.html)
Autodesk(2011).AutoCAD2012DXFReference.(Retrievedfromhttps://images.autodesk.com/adsk/files/autocad_2012_pdf_dxf-reference_enu.pdf) Ball,Alexander(2013).PreservingComputer-AidedDesign(CAD).DPCTechnologyWatchReport13-02.DigitalPreservationCoalition.(Retrievedfromhttps://www.dpconline.org/docs/technology-watch-reports/896-dpctw13-02-pdf/file)
CADAZZ(2004).CADsoftwarehistory.Retrievedfromhttp://cadazz.com/cad-software-history-1995-1997.htm
Chinn,A.(2009).ActivitiesintheDevelopmentofStandardsandTechnologyfortheLongTermRetentionof3DData.(RetrievedAugust,30.Retrievedfromhttp://www.ukoln.ac.uk/events/ltkr-2007/presentations/a-chinn.pdf)
Day,Martin(2006).TheDWGconundrum.In:AECMagazine.December(7)
Enlyft(2019).AutoCADvsSolidworks:WorldwideMarketShareCompared.(Retrievedfromhttps://enlyft.com/
autocad-vs-solidworks-worldwide-market-share-compared)
Evans,Tim(2016).FileobsolescenceattheADS?Retrievedfromhttps://dpconline.org/docs/miscellaneous/events/2016-events/1546-reformat-timevans/file
FACADE(2013)FinalReport:FACADE2:MITandHarvardCollaboration,”HarvardLibraryLab.Retrievedfromhttps://osc.hul.harvard.edu/liblab/sites/default/files/325_final_2013_0.pdf
Folk,M.,&Barkstrom,B.R.(2003,May).Attributesoffileformatsforlong-termpreservationofscientificandengineeringdataindigitallibraries.InJointConferenceonDigitalLibraries(JCDL),Houston,TX(Vol.1).(Retrievedfromhttps://www.researchgate.net/publication/228726593_Attributes_of_file_formats_for_long-term_preservation_of_scientific_and_engineering_data_in_digital_libraries) FreeCAD(n.d.)InWikipedia.(Retrievedfromhttps://en.wikipedia.org/wiki/FreeCAD)
Green,K.,Niven,K.,&Field,G.(2016).Migrating2and3DDatasets:PreservingAutoCADattheArchaeologyDataService.ISPRSInternationalJournalofGeo-Information,5(4),44.https://doi.org/10.3390/ijgi5040044
Heutelbeck,D.,Brunsmann,J.,Wilkes,W.,&Hundsdörfer,A.(2009,June).Motivationsandchallengesfordigitalpreservationindesignandengineering.InFirstInternationalWorkshoponInnovationinDigitalPreservation
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Lindlar,M.,andSaemann,H.(2014)TheDURAARKProject–Long-TermPreservationofArchitectural3D-Data.AnnualConferenceoftheInternationalCommitteeforDocumentation/theInternationalCouncilofMuseums(CIDOC2014).Dresden,Germany.(Retrievedfromhttp://www.cidoc2014.de/images/sampledata/cidoc/papers/ L-1_Lindlar_Saemann_paper.pdf)
Lowet,Wim(2016).BouwstenenvoordearchiveringvanhetdigitaalarchiefMaartenvanSeveren.VlaamsArchitectuurinstituut.(Retrievedfromhttps://www.vai.be/volumes/general/mvs_20160907_rapport_v1-3.pdf)
OpenDesignAlliance(2018).OpenDesignSpecificationfor.dwgfiles.Version5.4.1.(Retrievedfromhttps://www.opendesign.com/files/guestdownloads/OpenDesign_Specification_for_.dwg_files.pdf)
Ras,Marcel(2018).Preservationpolicy.Rotterdam.HetNieuweInstituut.Rog,J.andvanWijk,C.(2008).Evaluatingfileformatsforlong-termpreservation.NationalLibraryoftheNetherlands;TheHague,TheNetherlands.
Sheikh,Farooq(2019).WhatisaDWGfile?Retrievedfromhttps://wiki.fileformat.com/cad/dwg/
Shubert,H.(2008).Preservingdigitalarchivesatthecanadiancentreforarchitecture:GregLynn’sembryologicalhouse.Architectureetarchivesnumériques.L’architectureàl’èredunumérique:unenjeudemémoire.
Smith,MacKenzie(2009).CuratingArchitectural3DCADModels.In:TheInternationalJournalofDigitalCuration1no.2.Retrievedfromhttps://doi.org/10.2218/ijdc.v4i1.81
Stewart,K.,&Breitwieser,S.(2019).SCOPE:Adigitalarchivesaccessinterface.Code4LibJournal,(43).(Retrievedfromhttps://journal.code4lib.org/articles/14283)
Strong,Brad(2017).BrepvsVisrepModels.Retrievedfromhttps://transmagic.com/brep-vs-visrep-models/
Strong,Brad(2019).WhichGeometricModelingKernel?Retrievedfromhttps://transmagic.com/which-geometric-modeling-kernel/
Tatum,L.(2002).DocumentingDesign:ASurveyofState-of-the-ArtPracticeforArchivingArchitecturalRecords.ArtDocumentation:JournaloftheArtLibrariesSocietyofNorthAmerica,21(2),25-31.
Todd,Malcolm(2009).Fileformatsforpreservation.TheNationalArchives(DPCTechnologyWatchReportSeries09-02).
OpendesignAlliance(2018).OpenDesignSpecificationfor.dwgfilesVersion5.4.1.(Retrievedfromhttps://www.opendesign.com/files/guestdownloads/OpenDesign_Specification_for_.dwg_files.pdf) Vanstappen,Henk(2017).Pre-ingestborndigitalarchiefarchitectChristianKieckens-Rapport2:ProcedureIdentificatie.Antwerp,DATABLE/VAi.Retrievedfromhttps://www.projectcest.be/w/images/Db-2_Procedure_identificatie_v1_6.pdf
Vanstappen,Henk(2019).SketchUpindigitalarchives.Softwareandfile
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atformatanalysisandexplorationoftheoptionsfordigitalpreservation.Antwerp,Datable/VlaamsArchitectuurinstituut.
Walsh,T.(2015).PreservationandAccessofBorn-DigitalArchitecturalDesignRecordsinanOAIS-TypeArchive.Retrievedfromhttps://www.researchgate.net/publication/228726593_Attributes_of_file_formats_for_long-term_preservation_of_scientific_and_engineering_data_in_digital_libraries
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6.1. AutoCADsoftwarehistory
AutoCAD Release History AutoCAD1.0December1982(Release1)
AutoCAD1.2April1983(Release2)
AutoCAD1.3August1983(Release3)
AutoCAD1.4October1983(Release4)
AutoCAD2.0October1984(Release5)
AutoCAD2.1May1985(Release6)
AutoCAD2.5June1986(Release7)
AutoCAD2.6April1987(Release8)
AutoCADR9September1987codenameWhiteAlbum(Release9)
AutoCADR10October1988codenameAbbeyRoad(Release10)
AutoCADR11October1990codenameLetitBe(Release11)
AutoCADR12June1992(Release12)
AutoCADR13November1994(Release13)
AutoCADR14February1997codenameSedonaandPinetopfor14.01(Release14)
AutoCAD2000March1999codenameTahoe(Release15)
AutoCAD2000iJuly2000codenameBanff(Release16)
AutoCAD2002June2001codenameKirkland(Release17)
AutoCAD2004March2003codenameReddeer(Release18)
AutoCAD2005March2004codenameNeo(Release19)
AutoCAD2006March2005codenameRio(Release20)
AutoCAD2007March2006codenamePostrio(Release21)
AutoCAD2008March2007codenameSpago(Release22)
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atAutoCAD2009March2008codenameRaptor(Release23) AutoCAD2010March2009codenameGator(Release24) AutoCAD2011March2010codenameHammer(Release25) AutoCAD2012March2011codenameIronman(Release26) AutoCAD2013March2012codenameJaws(Release27) AutoCAD2014March2013codenameKeystone(Release28) AutoCAD2015March2014codenameLongbow(Release29) AutoCAD2016March2015codenameMaestro(Release30) AutoCAD2017March2016codenameNautilus(Release31) AutoCAD2018March2017codenameOmega(Release32) AutoCAD2019April2018codenamePi(Release33)
AutoCAD for MacOS Releases AutoCADforMacJune1992 AutoCADforMacR13[1994] AutoCAD2011forMacOctober2010(SledgeHammer) AutoCAD2012forMacAugust2011(IronMaiden) AutoCADLT2012forMacAugust2011(Ferris) AutoCADLT2013forMacAugust2012 AutoCAD2013forMacMarch2012(Jaws) AutoCADLT2014forMac AutoCAD2014forMac(Sandstone) AutoCAD2015forMac(Lightsaber) AutoCAD2016forMac(Mandalore) AutoCAD2017forMac(Naboo) AutoCAD2018forMacNov2017 S
ource:http
s://autod
esk.blog
s.com/betwee
n_the_
lines/autocad
-relea
se-history.htm
lSou
rce:http
s://autod
esk.blog
s.com/betwee
n_the_
lines/autocad
-relea
se-
history.html
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Version
DWGR1.0 DWGR1.2 DWGR1.40 DWGR2.05 DWGR2.10 DWGR2.21 DWGR2.22 DWGR2.50 DWGR2.60 DWGR9 DWGR10 DWGR11/12 DWGR13 DWGR14 DWG2000 DWG2004 DWG2007 DWG2010 DWG2013
DWG2018
Internal version name
MC0.0 AC1.2 AC1.40
AC1.50 AC2.10 AC2.21 AC1001,AC2.22 AC1002 AC1003 AC1004 AC1006 AC1009 AC1012 AC1014 AC1015 AC1018 AC1021 AC1024 AC1027
AC1032
Software release version name
AutoCADRelease1.0 AutoCADRelease1.2 AutoCADRelease1.40 AutoCADRelease2.05 AutoCADRelease2.10 AutoCADRelease2.21 AutoCADRelease2.22 AutoCADRelease2.50 AutoCADRelease2.60 AutoCADRelease9 AutoCADRelease10 AutoCADRelease11,12 AutoCADRelease13 AutoCADRelease14 AutoCAD2000,2000i,2002 AutoCAD2004,2005,2006 AutoCAD2007,2008,2009 AutoCAD2010,2011,2012 AutoCAD2013,2014,2015,2016,2017 AutoCAD2018,AutoCAD2019,AutoCAD2020 S
ource:http
s://en.wikiped
ia.org/wiki/.dw
g
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Below,theAutoCADversionnumbersandtheirmagicnumberinHexnotation.
Version
AutoCADR1.0Drawing AutoCADR1.2Drawing AutoCADR1.40Drawing AutoCADR2.05Drawing(new) AutoCADR2.05Drawing AutoCADR2.10Drawing AutoCADR2.21Drawing AutoCADR2.22-20xxDrawing(generic) AutoCADR2.22Drawing(new) AutoCADR2.22Drawing(old) AutoCADR2.5Drawing AutoCADR2.6Drawing AutoCADR9Drawing AutoCADR10Drawing AutoCADR11-12Drawing AutoCADR13Drawing(subtype10) AutoCADR13Drawing(subtype11) AutoCADR13Drawing AutoCADR14Drawing(subtype13)
Internal version name
MC0.0 AC1.2 AC1.40
AC2.50 AC1.50 AC2.10 AC2.21 AC10 AC1001 AC2.22 AC1002 AC1003 AC1004 AC1006 AC1009 AC1010 AC1011 AC1012 AC1013
Magic number
4D43302E30 4143312E32 4143312E3430 4143322E3530 4143312E3530 4143322E3130 4143322E3231 41433130 414331303031 4143322E3232 414331303032 414331303033 414331303034 414331303036 414331303039 414331303130 414331303131 414331303132 414331303133
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6.4. DWGandDXFfileformatspecificationsinPRONOM
AutoCADR14Drawing AutoCAD2000–2002Drawing AutoCAD2004–2006Drawing AutoCAD2007–2009Drawing AutoCAD2010–2012Drawing AutoCAD2013–2016Drawing AutoCAD2018–2019Drawing
AC1014
AC1015
AC1018
AC1021 AC1024
AC1027
AC1032
414331303134 414331303135
414331303138
414331303231
414331303234
414331303237
414331303332
Sou
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://mark0.net/soft-trid-e.htm
l
File format name
AutoCADDrawing AutoCADDrawing AutoCADDrawing AutoCADDrawing AutoCADDrawing AutoCADDrawing AutoCADDrawing AutoCADDrawing AutoCADDrawing AutoCADDrawing AutoCADDrawing AutoCADDrawing AutoCADDrawing
Version
1 1.2 1.3 1.4 2 2.1 2.2 2.5 2.6 R9 R10 R11/12 R13
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atAutoCADDrawing AutoCADDrawing AutoCADDrawing AutoCADDrawing AutoCADDrawing DrawingInterchangeFileFormat(ASCII) DrawingInterchangeFileFormat(Binary) DrawingInterchangeFileFormat(Binary) DrawingInterchangeFileFormat(Binary) DrawingInterchangeFileFormat(Binary) DrawingInterchangeFileFormat(Binary) DrawingInterchangeFileFormat(ASCII) DrawingInterchangeFileFormat(ASCII) DrawingInterchangeFileFormat(ASCII) DrawingInterchangeFileFormat(ASCII) DrawingInterchangeFileFormat(ASCII) DrawingInterchangeFileFormat(ASCII) DrawingInterchangeFileFormat(ASCII) DrawingInterchangeFileFormat(ASCII)
DrawingInterchangeFileFormat(ASCII) DrawingInterchangeFileFormat(ASCII) DrawingInterchangeFileFormat(ASCII) DrawingInterchangeFileFormat(ASCII) DrawingInterchangeFileFormat(ASCII) DrawingInterchangeFileFormat(ASCII)
R14 2000–2002 2004–2005 2010/2011/2012 2013/2014 Generic R11/12 R13 R14 2000–2002 2004–2005 1 1.2 1.3 1.4 2 2.1 2.2 2.5 2.6 R9 R10 R11/12 R13 R14
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2000–2002 2004/2005/2006 R10 2007/2008/2009 2010/2011/2012 2013/2014 1
