Ross Defence Science and Technology Organisation 506 Lorimer Street Fishermans Bend VIC 3207 Australia 61 3 9626 7000 williamoliverpeterrossdstodefencegovau Keywords Distributed simulation enumerations schema bstract An essential resource for those ID: 83849
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4.Permitsecientviewing(orprocessing)ofpartorallofthedocumentasrequired.Forexample,layoutofthedocumentmaybechanged.2.1MachineReadableFormatsTherehavebeenatleasttwopublishedattemptsatcreatingamachinereadableformat.TheInstituteforSimulationandTrainingproducedthe`DISDataDictionary',adatabaseofentity-typeenumer-ationsandDISmessagestructures.ItwasaMicrosoftAccessdatabaseandexploitedthereportandquerytoolsprovidedbyMicrosoftAccessandcompatibledatabaseen-gines.AnHTMLversionwasavailableontheInternet[7],thoughthedatabasecontenthasnotbeenupdatedsince1996.In2005thefollowingrequirementsforamachinereadableversionoftheenumerationsdocumentwereproposed[8]:1.Bothahumanreadabledocumentandatleastonema-chinereadableformatarerequired;2.theremustbeaprocesstoconvertbetweenthehumanreadabledocumentandthemachinereadableformat;3.anyconversiontoolsthatsupportthisprocessmustbeavailableatno-cost(orindustrystandard),andnotbeencumberedbyrestrictivelicensingconditions;4.anytoolsmustnothaveasteeplearningcurveorre-quireexpertlevelknowledgetouse;and5.anytoolsmustbeavailableforMicrosoftWindows.TheenumerationsmaintainerthenreleasedanXMLdoc-umentnamed`XMLencodingofDISEBV'(XoDIS),to-getherwithapartiallypopulatedXMLdatalecontainingentity-typeandvalue-pairenumerations.2.2AnImprovedFormatAthirdmachinereadableformatwaspublishedin2007.ThisimprovedontheXoDISproposal,asito eredafullypopulatedXMLdatale,encouragingmoreimmediateadoption.Italsousedasimpler,moregeneral,informa-tionschemathatdidnothavetobeupdatedeachtimeta-bleswereaddedorremovedfromthedocument.BoththeXoDISrequirementsandthe2007proposalhaveformedthebasisoftheSISO-REF-010XMLdocument.2.2.1WhichTechnologytoUse(orWhyXML)?Themainpurposeistohaveasinglesourceofinforma-tionthatcanbemadeeasilyaccessiblebybothhumansandcomputers.Therearetwoapproachesthatcanbetaken,haveahumanreadablemasterformatthatcanbeprocessedbyacomputer,oracomputerreadablemasterthatcanbeprocessedtobehumanreadable.TheXoDISrequire-mentsnotedpreviously,calledonMSWindowsavailabil-ity,howevermanysimulationsrunonolderworkstations,someonunusualmachines.Recentsimulationstypicallyrunonx86oramd64compatiblecomputers,andthusitisalsoessentialthatthetechnologybecrossplatform.Tech-nologiesthathavebeenproposedincludeStructuredQueryLanguage(SQL),MicrosoftAccess,theLightweightDi-rectoryAccessProtocol(LDAP)andplainCommaSepa-ratedValueles(CSV).Thepurposeoftheenumerationsdocumentistoactasarepositoryforsimulationenumerationsdata:itshouldnotputanyconstraintsonhowitisusedandimplemented.Thismeansthatitmustbeconvertibleintoaformatac-ceptabletotheenduser.Thisimpliestherequirementthatthemachinereadabledocumentbeeasilyconvertedtootherformats.ThedecisiontouseXMLcamefromthefactthatofallthetechnologiessuggested,XMLisanopenstandardfromtheWorldWideWebConsortium(W3C);XMLiswidelyusedandcrossplatform;Itsopennessandubiquityensuretherearemanytools,bothfreeandexpensive,openandproprietary;UnlikeLDAPorSQLitrequiresnoserversoftware;Ithasaformfordescribingtransformationstootherforms(XSLT—whichisitselfanopenstandard);XMLisadevelopmentofolderandproventechnolo-gies(bothSGMLandHTML);Itisatextformat,–Itisreadablebybothhumansandcomputers(al-thoughrawXMLisnotidealforhumans);–Therearemanyrevisioncontrolsystemsanddif-ferencetoolstocompareversions.2.2.2Whichinformationmodeltouse(orwhynotXoDIS)?Theoriginalenumerationsdocumentspeciedatotalof279tables,whereeachtablelistsenumeratedvaluesforthevariousDISProtocolDataUnit(PDU)elds.Thesetablesweregroupedtogetherandarrangedintosections.Eachsectionbeginswithabriefdescriptionofthetable,followedbythetableitself. Figure1:ThemachinereadableenumerationsdocumentXMLhierarchy.Notethatcrandcr_rangeelementsarenotshownastheycanbechildrenofanyelement(excepttherootelement).allowthereuseandextensionofelements,simplifyingthedesignoftheschema.TheXMLschemahierarchyhasanumberofgenericab-stracttypes,whichdenemostoftheattributes.Elementsthatappearinthemachinereadableenumerationsdocu-mentareinstancesoftypesthatinheritfromoneofthesegenerictypes.TheinformationmodelandXMLelementsintroducedinsection3areexpandedonbelow.4.1SchemaGenericTypesTheschemadenesanumberofabstracttypes.Anab-stracttypeinXMLcannotbeusedasaninstanceinadoc-ument.Thepurposeistodeneattributesorrestrictionsthatarecommontoanumberofelements,suchthatanotherXMLtypecanthenbederivedfromtheabstracttypeandinherititspropertiesaswellasadditsown.Theabstracttypesofthemachinereadableenumerationsdocumentare:generictable_tThisisthebasetypeforallelementsthatdeneatable.Itsattributesareshownintable5.genericentry_tThisisthebasetypeforallentitiesandobjects.Itsattributesareshownintable4.genericentrydescription_textendsgenericentry_tbyaddingamandatoryattributedescription(astring).genericentrystring_tisthebasetypeforallsin-glevaluedentriesthatarestrings.Itextendsgenericentrydescription_t,addingamandatoryattributevalue(astring).genericentrysingle_tisthebasetypeforallsinglevaluedentriesthatareintegers.Itextendsgenericentrydescription_t,addingamandatoryattributevalue(aninteger).genericentryrange_tisthebasetypeforallrangevaluesthatareintegers.Itextendsgenericentrydescription_t,addingtheat-tributesvalue_minandvalue_max(integers).4.2DocumentRootAllXMLdocumentsarerequiredtohaveasinglerootele-ment[12].Therootelementforthemachinereadableenu-merationsdocumentisebv.Itsattributesareshownintable6andthehierarchyhasbeenshowninsection3andgraph-icallyingure1. Nameannotation titleTitleofthedocument(e.g.SISO-REF-010-2010.1).releaseReleaseorversionnumber(e.g.Draft3,Final).hrefInternethyperlinkwherethisdocumentispublished.datePublicationdatespeciedinISO8601dateformat(YYYY-MM-DD).descriptionDescriptionofthedocument.organisationPublishingorganisation. Table6:AttributesoftheRootElement(ëv0;).keyMeta-datanameassociatedwiththecolumn—amandatoryattribute(astring).nameNameofthecolumn—amandatoryattribute(astring).enumrowextendsthetypegenericentrysingle_tbyallowingmetaelementsaschildren.enumrow_rangeextendsthetypegenericentryrange_tbyallowingmetaele-mentsaschildren.metapermitsarbitrarymeta-datatobeassociatedwithanenumeration.IthastwoattributeskeyMeta-datanameoridentier(e.g.units)—amandatoryattribute(astring).valueMeta-datavalue(e.g.meterspersecond)—amandatoryattribute(astring).4.5BiteldTableAbit-encodedvalueinDISisadatastructurewhereanumberofenumerationsarepackedintoarangeofbitsinaeld;thatisabitmaskcontainsanumberofenumera-tionvalues.Intheenumerationsdocumentabiteldtableshowstheenumerationscontainedinabit-encodedvalue.Biteldtablesarerepresentedbytheelementbitmaskwhileindividualbiteldsarerepresentedbybitmaskrowwhichcontainsenumrow(orenumrow_range)elementstorepresentanindividualenumerationvalue(orrow)inthetable.bitmaskextendsthetypegenerictable_tbyallowingchildelementsbitmaskrowandbitmaskrow_range.bitmaskrowextendsthetypegenericentrysingle_tbyallowingenumrowandenumrow_rangeelementsaschildren.bitmaskrow_rangeextendsthetypegenericentryrange_tbyallowingenumrowandenumrow_rangeelementsaschildren.4.6ComprehensiveEntityTypeThecetelementisusedtorepresentthebaseofthecom-prehensiveentitytypetables.Intheschemathecetel-ementcontainsalistofentityelements.Thesecorre-spondtothetablesinthepreviousEBV-DOC,thatis,theyareuniquelydenedbyacombinationofkind,domainandcountry.Beneaththeentityelementthereisahier-archicalstructureofcategory,subcategory,specificandextraelementsthatuniquelydeneanentity.cetextendsgenerictable_tbyallowingentityele-mentsaschildren.entityisaninstanceofentity_twhichextendsgenericentry_tbyallowingcategoryandcategory_rangeelements,andthefollowingattributes:kindamandatoryinteger.domainamandatoryinteger.countryamandatoryinteger.uidUniquenumericidentier.categoryextendsthetypegenericentrysingle_tbyaddingthemandatoryattributeuid(aninteger)andallowsthechildelementssubcategoryandsubcategory_range.category_rangeextendsthetypegenericentryrange_tbyaddingthemanda-toryattributeuid(aninteger)andallowsthechildelementssubcategoryandsubcategory_range.subcategoryextendsthetypegenericentrysingle_tbyaddingthemandatoryattributeuid(aninte-ger)andallowsthechildelementsspecificandspecific_range.subcategory_rangeextendsthetypegenericentryrange_tbyaddingthemanda-toryattributeuid(aninteger)andallowsthechildelementsspecificandspecific_range.specificextendsthetypegenericentrysingle_tbyaddingthemandatoryattributeuid(aninteger)and &#x/ele;&#xment;TheXMLenumerationsdocumenthasnodataastextnodes;alldataisencodedasattributesofelements,ratherthanastextnodesenclosedbyelements.Thiswasnotaconsciousdesigndecisionbutcameaboutastheauthorsoftheschemasimplychosetoencodetheinformationinthisway.6.4TheLackofDescriptiveTextTheXMLenumerationsdocumentdoesnotcontainthede-scriptivetextbeforeand/oraftertablesthatappearintheMSWordversion.Thedescriptivetextexistsatpresentinthetemplatestowhichthevarioustransformtoolswritetheirdata.Thisisapotentialproblemasitmeanstherearetwosourcesofdata.Itisgenerallygoodpracticetosep-aratedataandpresentation.Infact,theXMLlanguageschosenmakethisexplicit,XMLforthedataandXSLforthepresentationlogic.Havingtheenumerationsandthetextdescribingenumerationtables,inseparatedocuments(theXMLandtheXSLdocuments)meanstherearepoten-tiallytwoplacestoeditdata.Wheninitiallyembarkingondevelopingthemachineread-ableenumerationsdocument,agoalwastocreateahumanreadableversionthatmimickedtheexistingoneascloselyaspossible.AtthetimetheonlywaytoachievethiswastoputthetextintheXSLscript.InfutureitshouldbepossibletoputthistextintotheXMLleandremoveitfromtheXSLle,providingasmallnumberofstylechangescanbemadetothehumanread-ableform.6.5TheuseofTypename_ttoDescribeTypesTheschemamakesextensiveuseofabstracttypestodenetheelements.Forexample,theenumelementisaninstanceoftheenum_ttype.Theuseof_tattheendofatypenameisaconventiontheauthorsadoptedfromtheCprogram-minglanguage.Whilethisisperfectlyvalid,itisnottheusualXMLcon-vention.Itismorecommontoseesomevariationofthesocalledcamelcase,wherewordsarestrungtogetherandtherstletteriscapitalised.So,ourenumelementwouldbeaninstanceofenumTypeorEnumType.Aswithallstylecon-ventions,consistencyisusuallymoreimportantthantheconventionchosen.7ConclusionInthispaperwehavedetailedthedevelopmenthistoryofthemachinereadableenumerationsdocumentandde-scribedtheschemaintermsofitsconstituentelementsandattributes.HavingstartedwiththerequirementssetforthinXoDISitishopedthisevolutionofthedocumenthaspro-ducedaschemathatisbothrelativelyeasilyunderstood,yetcomprehensiveenoughtocapturealltheenumerationsdataandseewidespreadadoptioninthesimulationcom-munity.ItsrstformaluseistobethenextreleaseofSISO-REF-010.8References[1]G.Sauerborn,“Nonwordversion?,”1997.http://discussions.sisostds.org/default.asp?action=9&read=14433&fid=162&boardid=2.[2]T.DeCarlo,“LookingforenumdocinMSAccessformat,”1999.http://discussions.sisostds.org/default.asp?action=9&read=14488&fid=163&boardid=2.[3]B.Clay,“DISenumerationslist,”2003.http://discussions.sisostds.org/default.asp?action=9&read=14915&fid=167&BoardID=2.[4]G.Shanks,“MachinereadableDISEnumerations,”2005.http://discussions.sisostds.org/default.asp?action=9&read=15143&fid=31&BoardID=2.[5]D.Bruztman,“DISEnumerationDatabaseandXML,”2005.http://discussions.sisostds.org/default.asp?action=9&read=15188&fid=31&BoardID=2.[6]P.Ross,“Machinereadableenumerationsforim-proveddistributedsimulationinitialisationinteroper-ability,”inSimTecT2008ConferenceProceedings,(Melbourne,Australia),SimulationIndustryAssocia-tionofAustralia,SimulationIndustryAssociationofAustralia,12–15May2008.[7]InstituteforSimulationandTraining,“DISDataDic-tionary(on-lineversion).”http://siso.sc.ist.ucf.edu/dis-dd.[8]G.Shanks,“MachineReadableEnumerations-DISProductDevelopmentGroupMeeting,”inFallSim-ulationInteroperabilityWorkshop,no.05F-SIW-212,(Orlando,Florida,USA),September2005.