html5最新标准.docx
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html5最新标准.docx
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html5最新标准
Adddeveloper-viewstyles
HTML5
AvocabularyandassociatedAPIsforHTMLandXHTML
W3CRecommendation28October2014
Tableofcontents – 2Commoninfrastructure→
1.1 Introduction
1.1.1 Background
2.1.2 Audience
3.1.3 Scope
4.1.4 History
5.1.5 Designnotes
1.1.5.1 Serializabilityofscriptexecution
2.1.5.2 Compliancewithotherspecifications
3.1.5.3 Extensibility
6.1.6 HTMLvsXHTML
7.1.7 Structureofthisspecification
1.1.7.1 Howtoreadthisspecification
2.1.7.2 Typographicconventions
8.1.8 Privacyconcerns
9.1.9 AquickintroductiontoHTML
1.1.9.1 WritingsecureapplicationswithHTML
2.1.9.2 CommonpitfallstoavoidwhenusingthescriptingAPIs
3.1.9.3 HowtocatchmistakeswhenwritingHTML:
validatorsandconformancecheckers
10.1.10 Conformancerequirementsforauthors
1.1.10.1 Presentationalmarkup
2.1.10.2 Syntaxerrors
3.1.10.3 Restrictionsoncontentmodelsandonattributevalues
11.1.11 Suggestedreading
1 Introduction
1.1 Background
Thissectionisnon-normative.
TheWorldWideWeb'smarkuplanguagehasalwaysbeenHTML.HTMLwasprimarilydesignedasalanguageforsemanticallydescribingscientificdocuments,althoughitsgeneraldesignandadaptationsovertheyearshaveenabledittobeusedtodescribeanumberofothertypesofdocuments.
ThemainareathathasnotbeenadequatelyaddressedbyHTMLisavaguesubjectreferredtoasWebApplications.Thisspecificationattemptstorectifythis,whileatthesametimeupdatingtheHTMLspecificationstoaddressissuesraisedinthepastfewyears.
1.2 Audience
Thissectionisnon-normative.
Thisspecificationisintendedforauthorsofdocumentsandscriptsthatusethefeaturesdefinedinthisspecification,implementorsoftoolsthatoperateonpagesthatusethefeaturesdefinedinthisspecification,andindividualswishingtoestablishthecorrectnessofdocumentsorimplementationswithrespecttotherequirementsofthisspecification.
ThisdocumentisprobablynotsuitedtoreaderswhodonotalreadyhaveatleastapassingfamiliaritywithWebtechnologies,asinplacesitsacrificesclarityforprecision,andbrevityforcompleteness.Moreapproachabletutorialsandauthoringguidescanprovideagentlerintroductiontothetopic.
Inparticular,familiaritywiththebasicsofDOMisnecessaryforacompleteunderstandingofsomeofthemoretechnicalpartsofthisspecification.AnunderstandingofWebIDL,HTTP,XML,Unicode,characterencodings,JavaScript,andCSSwillalsobehelpfulinplacesbutisnotessential.
1.3 Scope
Thissectionisnon-normative.
Thisspecificationislimitedtoprovidingasemantic-levelmarkuplanguageandassociatedsemantic-levelscriptingAPIsforauthoringaccessiblepagesontheWebrangingfromstaticdocumentstodynamicapplications.
Thescopeofthisspecificationdoesnotincludeprovidingmechanismsformedia-specificcustomizationofpresentation(althoughdefaultrenderingrulesforWebbrowsersareincludedattheendofthisspecification,andseveralmechanismsforhookingintoCSSareprovidedaspartofthelanguage).
Thescopeofthisspecificationisnottodescribeanentireoperatingsystem.Inparticular,hardwareconfigurationsoftware,imagemanipulationtools,andapplicationsthatuserswouldbeexpectedtousewithhigh-endworkstationsonadailybasisareoutofscope.Intermsofapplications,thisspecificationistargetedspecificallyatapplicationsthatwouldbeexpectedtobeusedbyusersonanoccasionalbasis,orregularlybutfromdisparatelocations,withlowCPUrequirements.Examplesofsuchapplicationsincludeonlinepurchasingsystems,searchingsystems,games(especiallymultiplayeronlinegames),publictelephonebooksoraddressbooks,communicationssoftware(e-mailclients,instantmessagingclients,discussionsoftware),documenteditingsoftware,etc.
1.4 History
Thissectionisnon-normative.
Foritsfirstfiveyears(1990-1995),HTMLwentthroughanumberofrevisionsandexperiencedanumberofextensions,primarilyhostedfirstatCERN,andthenattheIETF.
WiththecreationoftheW3C,HTML'sdevelopmentchangedvenueagain.AfirstabortiveattemptatextendingHTMLin1995knownasHTML3.0thenmadewaytoamorepragmaticapproachknownasHTML3.2,whichwascompletedin1997.HTML4quicklyfollowedlaterthatsameyear.
Thefollowingyear,theW3CmembershipdecidedtostopevolvingHTMLandinsteadbeginworkonanXML-basedequivalent,calledXHTML. ThiseffortstartedwithareformulationofHTML4inXML,knownasXHTML1.0,whichaddednonewfeaturesexceptthenewserialization,andwhichwascompletedin2000.AfterXHTML1.0,theW3C'sfocusturnedtomakingiteasierforotherworkinggroupstoextendXHTML,underthebannerofXHTMLModularization.Inparallelwiththis,theW3CalsoworkedonanewlanguagethatwasnotcompatiblewiththeearlierHTMLandXHTMLlanguages,callingitXHTML2.
AroundthetimethatHTML'sevolutionwasstoppedin1998,partsoftheAPIforHTMLdevelopedbybrowservendorswerespecifiedandpublishedunderthenameDOMLevel1(in1998)andDOMLevel2CoreandDOMLevel2HTML(startingin2000andculminatingin2003).Theseeffortsthenpeteredout,withsomeDOMLevel3specificationspublishedin2004buttheworkinggroupbeingclosedbeforealltheLevel3draftswerecompleted.
In2003,thepublicationofXForms,atechnologywhichwaspositionedasthenextgenerationofWebforms,sparkedarenewedinterestinevolvingHTMLitself,ratherthanfindingreplacementsforit.ThisinterestwasbornefromtherealizationthatXML'sdeploymentasaWebtechnologywaslimitedtoentirelynewtechnologies(likeRSSandlaterAtom),ratherthanasareplacementforexistingdeployedtechnologies(likeHTML).
AproofofconcepttoshowthatitwaspossibletoextendHTML4'sformstoprovidemanyofthefeaturesthatXForms1.0introduced,withoutrequiringbrowserstoimplementrenderingenginesthatwereincompatiblewithexistingHTMLWebpages,wasthefirstresultofthisrenewedinterest.Atthisearlystage,whilethedraftwasalreadypubliclyavailable,andinputwasalreadybeingsolicitedfromallsources,thespecificationwasonlyunderOperaSoftware'scopyright.
TheideathatHTML'sevolutionshouldbereopenedwastestedataW3Cworkshopin2004,wheresomeoftheprinciplesthatunderlietheHTML5work(describedbelow),aswellastheaforementionedearlydraftproposalcoveringjustforms-relatedfeatures,werepresentedtotheW3CjointlybyMozillaandOpera.TheproposalwasrejectedonthegroundsthattheproposalconflictedwiththepreviouslychosendirectionfortheWeb'sevolution;theW3CstaffandmembershipvotedtocontinuedevelopingXML-basedreplacementsinstead.
Shortlythereafter,Apple,Mozilla,andOperajointlyannouncedtheirintenttocontinueworkingontheeffortundertheumbrellaofanewvenuecalledtheWHATWG.Apublicmailinglistwascreated,andthedraftwasmovedtotheWHATWGsite.Thecopyrightwassubsequentlyamendedtobejointlyownedbyallthreevendors,andtoallowreuseofthespecification.
TheWHATWGwasbasedonseveralcoreprinciples,inparticularthattechnologiesneedtobebackwardscompatible,thatspecificationsandimplementationsneedtomatchevenifthismeanschangingthespecificationratherthantheimplementations,andthatspecificationsneedtobedetailedenoughthatimplementationscanachievecompleteinteroperabilitywithoutreverse-engineeringeachother.
ThelatterrequirementinparticularrequiredthatthescopeoftheHTML5specificationincludewhathadpreviouslybeenspecifiedinthreeseparatedocuments:
HTML4,XHTML1,andDOM2HTML.Italsomeantincludingsignificantlymoredetailthanhadpreviouslybeenconsideredthenorm.
In2006,theW3CindicatedaninteresttoparticipateinthedevelopmentofHTML5afterall,andin2007formedaworkinggroupcharteredtoworkwiththeWHATWGonthedevelopmentoftheHTML5specification.Apple,Mozilla,andOperaallowedtheW3CtopublishthespecificationundertheW3Ccopyright,whilekeepingaversionwiththelessrestrictivelicenseontheWHATWGsite.
Foranumberofyears,bothgroupsthenworkedtogetherunderthesameeditor:
IanHickson.In2011,thegroupscametotheconclusionthattheyhaddifferentgoals:
theW3CwantedtodrawalineinthesandforfeaturesforaHTML5Recommendation,whiletheWHATWGwantedtocontinueworkingonaLivingStandardforHTML,continuouslymaintainingthespecificationandaddingnewfeatures.Inmid2012,aneweditingteamwasintroducedattheW3CtotakecareofcreatingaHTML5RecommendationandprepareaWorkingDraftforthenextHTMLversion.
Sincethen,theW3CHTMLWGhasbeencherrypickingpatchesfromtheWHATWGthatresolvedbugsregisteredontheW3CHTMLspecificationormoreaccuratelyrepresentedimplementedrealityinUAs.Attimeofpublicationofthisdocument,patchesfromthe WHATWGHTMLspecification havebeenmergeduntilrevision8152 inclusive.TheW3CHTMLeditorshavealsoaddedpatchesthatresultedfromdiscussionsanddecisionsmadebytheW3CHTMLWGaswellabugfixesfrombugsnotsharedbytheWHATWG.
AseparatedocumentispublishedtodocumentthedifferencesbetweentheHTMLspecifiedinthisdocumentandthelanguagedescribedintheHTML4specification. [HTMLDIFF]
1.5 Designnotes
Thissectionisnon-normative.
ItmustbeadmittedthatmanyaspectsofHTMLappearatfirstglancetobenonsensicalandinconsistent.
HTML,itssupportingDOMAPIs,aswellasmanyofitssupportingtechnologies,havebeendevelopedoveraperiodofseveraldecadesbyawidearrayofpeoplewithdifferentprioritieswho,inmanycases,didnotknowofeachother'sexistence.
Fe
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