Note:

The notation "[X,Y]" denotes a closedinterval fromX toY, includingX andY;"[X,Y)" denotes a right half-openinterval fromX toY, includingX but not includingY;"(X,Y]" denotes a left half-openinterval fromX toY, not includingX but includingY;"(X,Y)" denotes an openinterval fromX toY, not includingX orY.

Note:

In this example, thep element is used as a presentationalelement rather than as a semantic element, i.e., as a linguistic paragraph.It is up to an author to determine which TTML elements are used to conveythe intended meaning. For instance, this example could be written to usetiming onspan elements in order to preserve the integrity ofsemantic paragraphs.

Note:

For example, the phrases "treat X as an error" and "consider Xas an error" are to be read as mandatory requirements in the context of use. Similarly, if the specificationprose is "X must apply", "X applies", or "X is mandatory", and "X" is further defined as "X is Y and Z",then, by transitive closure, this last declarative phrase is to be read as "Y is mandatory" and"Z is mandatory" in the context of use.

Note:

With the exception ofN.1 Element Derivation, the (possibly namespace qualified) name of an attributeis prefixed with an '@' (COMMERICAL AT) character in order to disambiguate between the attribute and a like-named element type, in which casethe '@' character is not intended to be part of the literal name of the attribute. For example,@ttm:agentrefers to thettm:agent attribute, whilettm:agent refers tottm:agent element.

Note:

Although they are expressed in well-formed XML, example code fragments depicted herein are not intended to be complete, valid TTML documents;rather, they are generally abbreviated in order to focus on the intended example. In particular, fragments will typically need to be augmentedwith additional elements and/or attributes in order to satisfy TTML document conformance requirements.

Note:

The conformance requirements defined by this section are scoped to processors that operate on staticrepresentations of a TTMLdocument instance. In particular,processors that modify a TTMLdocument instance, such as anauthoring or editing tool, are not governed by this specification except to the extent that the finalresult of performing a series of modifications to a TTMLdocument instancesatisfies the formal validity of TTML Content as defined by3.1 Document Conformance.

3.2.1 Generic Processor Conformance

A TTML2content processor conforms to this specification if the followinggeneric processor criteria aresatisfied:

1. The processor provides at least one mechanism for notionallyinstantiating areduced xml infosetrepresentation of a conformantdocument instance.

2. The processor performsprofile processing.

   Note:

   The performance ofprofile processing implies a certain degree of partial validation,short of performing the[validate document] proceduredescribed in the next item below. In particular, the syntactic expression of profile related vocabulary and any essential syntactic orsemantic constraint that applies to the usage of this vocabulary are expected to be nominally verified by an implementation prior to makinguse of this vocabulary. Ifprofile processing is completed without detecting a significant violationof a syntactic or semantic constraint, then more complete validation may be performed by the[validate document] procedure.

3. If a processor is avalidating content processor, then it

   1. provides at least one mechanism to implicitly or explicitly associate thereduced xml infoset representationof a candidatedocument instance with one of theAbstract Document Types defined by4 Document Types; and

   2. performs the[validate document] procedure.

   Note:

   This specification does not define a strict order between the performance ofvalidation processingand the performance ofprofile processing described in the previous item above. In particular, these twoprocessing steps may be interleaved (or repeated) such that both are completed prior to performing further (transformation or presentation) processingon adocument instance.

   Notwithstanding the above, there is an implied order relationship betweenvalidation processingandprofile processing; specifically, in order to performvalidation processing, it is necessary to resolve the value of theeffective validation profile, for which value it is necessary to resolve the value of theeffective content profile, or if that value isnull, then resolve the value of theeffective processor profile, the latter two values of which are obtained duringprofile processing.

   Note:

   For an example of interleavingvalidation processing andprofile processing, consider the following scenario (in the given order):

   • verify well-formedness of input document source (validation processing);

   • instantiate input document source as potentially valid abstract document instance (general processing);

   • initialize validation state using built-in application semantics (validation processing);

   • initialize profile state using built-in application semantics (profile processing);

   • validate validation related vocabulary (validation processing);

   • update validation state using valid validation related vocabulary (validation processing);

   • validate profile related vocabulary (validation processing);

   • update profile state using valid profile related vocabulary (profile processing);

   • perform abort steps of[abort ifunsupported processor profile] procedure (profile processing);

   • validate entire document, re-validating validation and profile vocabulary as required based on new profile state (validation processing);

   • if processing not aborted, continue with transformation or presentation processing (general processing).

4. The processor does nota priori reject or abort theprocessing of a conformantdocument instanceunless:

   1. the processor does not support some required(mandatory) feature specified or implied by a TTML profiledeclared to apply to thedocument instance; or

   2. avalidation error occurs when performing the[validate document] procedure.

5. The processor supports all mandatory processing semantics defined by this specification.

   Note:

   The phrasemandatory semantics refers to all explicit use of the conformancekey phrasesmust andmust not as well as anydeclarative statement that can be reasonably inferred from such key phrases.

   Note:

   Support for themandatory semantics of afeature orextension applies only when thefeature orextension is supported by a TTMLcontent processor.

6. If the processor supports some optional processing semantics defined by this specification,then it does so in a manner consistent with the defined semantics.

   Note:

   The phraseoptional semantics refers to all explicit use of the conformancekey phrasesshould,should not,may, andmay not,as well as any declarative statement that can be reasonably inferred from such key phrases.

3.2.2 Transformation Processor Conformance

A TTMLcontent processor is a conformant TTML2transformation processor ifthe following criteria are satisfied:

1. The processor satisfies all requirements specified by3.2.1 Generic Processor Conformance.

2. The processor supports the TTML Transformation profile as specifiedbyG.3 TTML2 Transformation Profile.

3. The processor supports the DFXP Transformation profile as specifiedbyG.6 DFXP Transformation Profile.

3.2.3 Presentation Processor Conformance

A TTMLcontent processor is a conformant TTML2presentation processor ifthe following criteria are satisfied:

1. The processor satisfies all requirements specified by3.2.1 Generic Processor Conformance.

2. The processor supports the TTML Presentation profile as specifiedbyG.2 TTML2 Presentation Profile.

3. The processor supports the DFXP Presentation profile as specifiedbyG.5 DFXP Presentation Profile.

4. The processor performs11.3.1.3 Intermediate Synchronic Document Construction and11.3.1.4 Synchronic Flow Processing.

Note:

The definitions ofTransformation Processor Conformance andPresentation Processor Conformance specified above requirethat each of these types of processors support (at a minimum) two specific profiles, a type specific profile defined by[TTML1]and a type specific profile defined by this specification.

Notwithstanding this requirement, it is possible to construct aTTMLcontent processorthat performs transformation or presentation processing functions and satisfiesGeneric Processor Conformance requirements but supports neither ofthe profiles required byTransformation Processor Conformance orPresentation Processor Conformance, and, instead,supports only profile(s) defined outside the scope of this specification. In such a case, the processor may be claimed to becompliant withGeneric Processor Conformance, and, further, be aTTMLtransformation processor or aTTMLpresentation processor,but may not claim compliance withTransformation Processor Conformance orPresentation Processor Conformance.

3.4.1 Forward Compatibility

A conforming TTML1 processor may be able to process a TTML2content document instance, provided it ignores unknown vocabulary and ignores known vocabulary that appears in a context where it is not permitted in a conforming TTML1content document instance; however, such processing may discard or fail to present content, or may present content differently than intended when processed by a conforming TTML2 processor.

3.4.2 Backward Compatibility

TTML2 is designed such that:

• A conforming TTML1content document instance is a conforming TTML2content document instance.

• A conforming TTML2 processor processes a conforming TTML1content document instance such that the output produced by the TTML2 processor is within the variations allowed per TTML1; however, it may emit warnings if it encounters deprecated features.

Note:

The schemas referenced by this specification do not validate all syntactic constraintsdefined by this specification, and, as such, represent a superset of conformantTTML Content. In particular, performing validation with one of the abovereferenced schemas may result in afalse positive indication of validity.For example, both the RNC and XSD schemas specifythat atts:fontFamily attribute mustsatisfy thexsd:string XSD data type; however, this data type is a supersetof the values permitted to be used with thetts:fontFamily attribute.

In addition, the RNC schema may produce afalse negativeindication of validity when using thexml:id attribute with an element ina foreign namespace, thus representing a subset of conformant TTML Content. This isdue to a specific limitation in expressing wildcard patterns involvingxsd:IDtyped attributes in Relax NG schemas. Note that this specification defines theformal validity of adocument instance to be based on anabstract document instance fromwhich all foreign namespace elements and attributes have been removed. Therefore, theexceptional reporting of this false negative does not impact the formal assessmentofdocument instance validity.

Note:

The schemas referenced by this specification are intended for use after the pruning steps (1)-(3) specified by4 Document Types have been applied.

Note:

A conformingGeneric Processor is required to support the ingestion and processingof atimed text content document.

Note:

A conformingGeneric Processor is not required to support the ingestion or processingof atimed text intermediate document.

Note:

A conformingGeneric Processor is recommended, but not required to support the ingestion or processingof atimed text profile document. However, acontent processorthat claims to support thehttp://www.w3.org/ns/ttml/feature/#profile feature is required to support this (ingestion and processing ofatimed text profile document).

Note:

In a specificdocument instance, it is not required that the defaultprefixes shown above be used. Any prefix or namespace binding that satisfies the constraintsof XML Namespaces[XML Namespaces 1.0] may be used that is associated with the specified namespace URI.

Note:

If a reference to an element type is used in this specification and the nameof the element type is not namespace qualified, then the TT Namespace applies.

If a reference to an attribute is used in this specification and the nameof the attribute is not namespace qualified, then the attribute is implicitly qualified bythe element type with which it is used. That is, the attribute resides in the so-calledper-element-type namespace partition[NSOriginal], the members of which are interpreted in accordance with the definition of the element type on which they appear.

For certain namespaces defined above, the default prefixis specified asnone if no XML vocabulary is defined inthe namespace by this specification (nor expected to be defined in afuture version of this specification). In such cases, the use of thenamespace URI is for purposes other than defining XML vocabulary,e.g., for designating profiles, features, extensions and fordereferencing standard profile definitions.

5.2.1 Introduction

This sub-section is non-normative.

A given profile may be used by a Timed Text Markup Language content author for one of two functions: (1) to declare that adocument instance adheres to a collection of constraints on whatvocabulary is used and how it is used, or (2) to declare that aprocessor must satisfy certain conditions on howcontent is processed. The first of these functions is termed acontent profile, whilethe second is termed aprocessor profile.

Acontent profile is used to allow an author to declare, at authoring time,what constraints the author intends to apply to adocument instance. Such adeclaration permits downstream processors to perform content validation or verification, as well as to guide or limit subsequenttransformation or editing of content in order to maintain adherence to an author specified content profile. In addition, adownstream processor may use a content profile declaration to perform an early determination of its ability to process the featuresimplied by the content profile.

Content profiles are declared by using (1) thettp:contentProfilesattribute on the roottt element, (2) one or more top-levelttp:profileelements of typecontent, or (3) a combination of these two mechanisms. If not declared, no content profile is implied.

Aprocessor profile is used to allow an author to declare, at authoring time,what processing must be supported when processing adocument instance, such that, if aprocessor is not able to perform the indicated processing, then processing should be aborted. Such a declaration permits downstreamprocessors to avoid processing content that cannot be processed in a manner that meets the requirements of the content author.

Processor profiles are declared by using (1) thettp:processorProfilesattribute on the roottt element, (2) one or morettp:profileelements of typeprocessor, or (3) thettp:profile attributeon the roottt element. If not declared, a processor profile is inferred from a declared content profile or from adefault processor profile.

A content author is not limited to using a single profile, but may make reference to multiple profiles of either type, i.e.,multiple content profiles and/or multiple processor profiles. When multiple profiles are referenced, their respective specificationsare combined to form a single effective content profile that applies to the document and a single effective processor profilethat applies to a processor when processing the document. In addition, an author is not limited to making reference to externallydefined profiles, but may define one or more profiles inline within a document.

5.2.2 Profile Examples

This sub-section is non-normative.

An example of an author definedadditive, derived profile of the TTML Presentationprofile is shownbelow inExample Fragment – TTML Additive Profile.

<tt xml:lang="" xmlns="http://www.w3.org/ns/ttml"> <head>   <profile use="ttml2-presentation" xmlns="http://www.w3.org/ns/ttml#parameter">     <features xml:base="http://www.w3.org/ns/ttml/feature/">       <feature value="required">#fontStyle-italic</feature>     </features>   </profile> </head> <body/></tt>

5.2.3 Profile Designators

A profile is referenced in one of two ways according to whether the profile is defined externally to the referring document oris defined inline within the referring document. When defined externally, a profile is referenced by means of an<absolute-profile-designator> or<relative-profile-designator> expression.When defined internally (inline), a profile is referenced either implicitlyor by means of a<fragment-profile-designator> expression.

A profile designator must adhere to the<uri> value syntax.If the profile designator is expressed as a relative URI,then it must be absolutized by using the TT Profile Namespace value asthe base URI.

All profile designators which have the TT Profile Namespace as a prefix but are otherwise not listed inTable 5-2 – Profiles are reserved for future standardization, and must not appear in a conformantdocument instance. Nothwithstanding this constraint, a profile designator is not restricted to the set of designators enumeratedinTable 5-2 – Profiles, but may be any URI that feasibly dereferences a TTMLprofile definition documentprovided it does not use the TT Profile Namespace as a prefix.

5.2.4 Profile Semantics

5.3.1 Validation Semantics

5.4.1 Core Catalog

The core vocabulary catalog is intended to satisfy the needs ofTTML while providing a baseline vocabulary for future profiles. This vocabularyis divided into distinct categories, specified in detailin the following sections:

• 6 Profile

• 7 Parameter

• 8 Content

• 9 Embedded Content

• 10 Styling

• 11 Layout

• 12 Timing

• 13 Animation

• 14 Metadata

The core element vocabulary specified for use with adocument instance is enumerated inTable 5-3 – Element Vocabulary.

Element vocabulary groups that are used in defining content modelsfor TTML element types are enumerated inTable 5-4 – Element Vocabulary Groups.

The attribute vocabulary specified for use with the core vocabularycatalog is enumerated inTable 5-5 – Attribute Vocabulary.

5.4.2 Extension Catalog

The extension vocabulary catalog is intended for use by futureprofiles of TTML, and is not further definedby this version of TTML.

In addition to standardized extension vocabulary, a conformingdocument instance may contain arbitrary namespace qualifiedelements that reside in any namespace other than those namespacesdefined for use with this specification. Furthermore, a conformingdocument instance may contain arbitrary namespace qualifiedattributes on TTML defined vocabulary where such attributes reside inany namespace other than those defined for use with thisspecification.

Note:

The sub-sections of this section are ordered logically (from highest to lowest level construct).

6.1.1 ttp:profile

Thettp:profile element is used to specify acontent profile or aprocessor profile.Aprocessor profile specifies acollection of required (mandatory) and optional (voluntary) features and extensions that must ormay be supported by acontent processor in order to process adocument instance that makes (or may make) use of such features andextensions.Acontent profile specifies acollection of prohibited, required, and optional features and extensions that, respectively,must not, must, and may be present in adocument instance that declares itsadherence to the profile.

This specification defines two distinct contexts of use for thettp:profile element:

• as a child of thehead element or attp:profile element within a TTMLdocument instance;

• as the root element of a TTMLprofile definition documentinstance;

When attp:profile element appears within a TTMLdocument instance,its purpose is to express authorial intentions about (1) whichfeatures and extensions must or may be supported by a recipientcontent processor in order to process that document or (2) which features and extensions must not, must, or may beincluded or otherwise used in thatdocument instance.

When attp:profile element is used by a TTMLprofile definition document instance,it serves to publish a machinereadable specification of a specific TTML profile that may be referenced by TTMLdocument instances.This specification defines a number of standardProfile Definition Documents inG Standard Profiles.

Thettp:profile element accepts as its children zero or moreelements in theMetadata.class element group, followed by either (1)zero or morettp:features elements followed byzero or morettp:extensions elements or (2)zero or morettp:profile elements.When attp:profile element contains a childttp:profile element, then the child is referred to asanested profile and the parent is referred to as anesting profile;otherwise it is referred to as anon-nesting profile.

<ttp:profile  combine = ("leastRestrictive" |"mostRestrictive" |"replace") : replace  designator =xsd:string  type = ("processor" |"content") : processor  use =xsd:stringxml:base =<uri>xml:id = IDContent:Metadata.class*, ((ttp:features*,ttp:extensions*)|ttp:profile*)</ttp:profile>

Thetype attribute is used to determine whether a profile is acontent profile or aprocessor profile. If not specified,the profile is considered to be aprocessor profile.If attp:profile element references abaseline profile or anested profile, then the type of the referenced profile must be the same as the type of the referencing profile. Forexample, attp:profile element that defines aprocessor profile may only make reference to otherprocessor profiles, and may not reference acontent profile.

Thecombine attribute is used to specify howfeature or extension specifications are combined in the case thatmultiple specifications apply to the same feature or extension, respectively.

If the value of thecombine attribute isreplace, then alexically subsequent feature or extension specification replaces a lexically priorspecification, where specification elements are ordered as follows:

1. specifications defined by abaseline profile referenced by auseattribute;

2. specifications defined by descendantttp:profile elements in post-ordertraversal order;

3. specifications defined as descendantttp:feature orttp:extensionelements in post-order traversal order.

If the value isleastRestrictive, then the least restrictive specification value applies;if the value ismostRestrictive, then the most restrictive specification valueapplies. The order of restrictiveness is as follows (from least to most):optional,required,prohibited.

If thecombine attribute is not specified, then replacement semantics apply.

If specified, thedesignator attribute must adhere to the<absolute-profile-designator> value syntax.Adesignator attribute maybe specified on attp:profile element that appears in a TTMLdocument instance, and, if not specified,the defined profile is considered to be an undesignated profile.Adesignator attribute shouldbe specified on attp:profile element that appears in a TTMLprofile definition document instance,and, if not specified, the defining context (e.g., an external specification) must specifya designator in its accompanying definition text.

If specified, theuse attribute must adhere to the<uri> value syntax, and, furthermore, must denote a profile designator inaccordance with5.2 Profiling. In this case,the profile designator must refer to (1) a standard, predefinedprofile definition document as defined by6 Profile,or (2) a feasibly dereferenceable resource representing a validProfile DefinitionDocument instance. In either case, the referenced profile serves as thebaseline profile of the specifyingttp:profile element.

If theuse attribute is not specified, then thebaseline profileof thettp:profile element must be considered to bethe empty (null) profile, i.e., an undesignated profile definition containing nofeature or extension specifications.

The combined profile specification setCPSS of features and extensions of a profilePis determined according to the following ordered rules, where merging a specificationSintoCPSS entails applying a combination method in accordance with the specified(or default) value of thecombine attribute, and where merging a combined specification setCPSS'  intoCPSS entails merging each ordered specification ofCPSS'  intoCPSS:

1. initializeCPSS to the empty set;

2. if ause attribute is present, then mergethe combined specification set of the referencedbaseline profile intoCPSS;

3. for eachttp:profile child of theP,using a post-order traversal, merge the combined specification set of the child profileintoCPSS;

4. for eachttp:feature andttp:extension child of thettp:profile element,using a post-order traversal, merge the feature or extension specificationintoCPSS.

A conformant TTML processor is not required to be able todereference aprofile definition document that is not one of thestandard, predefined profiles defined byG Standard Profiles. Furthermore,a conformant TTML processor may make use of a built-in, staticform of each standard, predefined profile so as not to requiredereferencing a network resource.

If a TTML processor is unable to dereference a non-standardprofile definition document, then it must not further process thedocument without the presence of an explicit override from an end-useror some implementation specific parameter traceable to an end-user orto a user or system configuration setting. If a TTML processor abortsprocessing of adocument instance due to the inability toreference a non-standardprofile definition document, then someend-user notification should be given unless the end-user or systemhas disabled such a notification, or if the processor does not permitor entail the intervention of an end-user.

A conformant TTML processor is not required to be able to support acombined profile oranesting profile. If(1)combined profiles are not supported and the processing of aprofilewould cause it to be considered acombined profile, or(2)nesting profiles are not supported and the processing of aprofilewould cause it to be considered anesting profile,then further processing of theprofile must not occur without the presence of an explicit override from an end-useror some implementation specific parameter traceable to an end-user or to a user or system configuration setting. If a TTML processor abortsprocessing of adocument instance due to lack of support forcombined profiles ornesting profiles,then some end-user notification should be given unless the end-user or system has disabled such a notification,or if the processor does not permit or entail the intervention of an end-user.

Thettp:profile element is illustrated by the following example.

<ttp:profile use="ttml2-presentation">  <ttp:features xml:base="http://www.w3.org/ns/ttml/feature/">    <ttp:feature>#text-outline</ttp:feature>  </ttp:features></ttp:profile>

6.1.2 ttp:features

Thettp:features element is a container element used to groupinformation about feature support and usage requirements.

Thettp:features element accepts as its children zero or moreelements in theMetadata.class element group, followed byzero or morettp:feature elements.

<ttp:featuresxml:base =<uri> :TT Feature Namespacexml:id = IDContent:Metadata.class*,ttp:feature*</ttp:features>

If specified, thexml:baseattribute must (1) adhere to the<uri> value syntax, (2) express an absolute URI thatadheres to[XML Base] and,(3) express a feature namespace as defined byE.1 Feature Designations. If not specified, thexml:base attribute's defaultvalue applies, which is the TT Feature Namespace.

Thexml:base attribute isused to permit the abbreviation of feature designation URIs expressedby childttp:feature elements.

6.1.3 ttp:feature

Thettp:feature element is used to specifyinformation about support and usage requirements for a particular feature.

<ttp:feature  extends =xsd:string  restricts =xsd:string  value = ("optional" |"required" |"use" |"prohibited") :see prose belowxml:id = IDContent: #PCDATA</ttp:feature>

The children of thettp:feature element must express a non-emptysequence ofcharacter information items the concatenation of which adheres to the<uri> value syntax.

If specified, theextends attribute and/or therestrictsattribute must (1) adhere to the<uri> value syntax, and(2) express a feature designation as defined byE.1 Feature Designations.

Theextends attribute may be used to indicate that the feature being definedis, from either (or both) a syntactic or (and) semantic perspective, a proper superset of thefeature referenced by theextends attribute.Therestricts attribute may be used to indicate that the feature being definedis, from either (or both) a syntactic or (and) semantic perspective, a proper subset of thefeature referenced by therestricts attribute.If anextends attribute is specified, then arestricts attribute mustnot be specified on attp:feature element; likewise, if arestricts attributeis specified, then anextends attribute must not be specified.

If the URI expressed by (1) the content of thettp:featureelement, (2) theextends attribute, or (3) therestricts attributeis a relative URI, then, when combined with thefeature namespace value expressed by thexml:base attribute of thenearest ancestorttp:features element, it must express anabsolute URI. In either case (original absolute URI or resultingabsolutized URI), the URI expressed by thettp:featureelement must further adhere to the syntax of a feature designation asdefined byE.1 Feature Designations, and, furthermore,the specific designation that appears in this URI, i.e., the portion of the feature designationthat starts with the fragment identifier separator '#', mustbe defined by this specification or some published version thereof (thathas achieved REC status).

If the URI expressed by the content of thettp:feature element,by theextends attribute, or by therestricts attributeis a relative URI, then anxml:base attribute should bespecified on the nearest ancestorttp:features element.

Thevalue attribute specifies constraints on support for or use ofthe designated feature according to the profile type.

If the profile is aprocessor profilethen the following semantics apply:

• if the value of thevalue attributeisoptional, then a processor may but neednot implement or otherwise support the feature in order to process the document;

• if the value isrequired, then perform the following steps:

  1. if the feature is implemented or otherwise supported by a processor, then continue processingthe document;

  2. otherwise, if(1) theextends attribute is specified on thisttp:feature element,(2) the value of theextends attribute designates a feature that is implemented or otherwise supported bya processor, and(3) the computed value of thettp:permitFeatureNarrowingproperty of the roottt element is notfalse,then continue processing the document;

  3. otherwise, if(1) therestricts attribute is specified on thisttp:feature element,(2) the value of therestricts attribute designates a feature that is implemented or otherwise supported bya processor, and(3) the computed value of thettp:permitFeatureWideningproperty of the roottt element is notfalse,then continue processing the document;

  4. otherwise, abort processing the document unless overridden by the end-user or some implementation specific parametertraceable to an end-user or to a user or system configuration setting.

• if the value attribute is not specified, then the feature specificationmust be interpreted as if the valuerequired were specified;

If the profile is acontent profilethen the following semantics apply:

• if the value of thevalue attributeisoptional, then the feature may but need not appear in a document thatclaims conformance with that profile;

• if the value of thevalue attributeisrequired, then the feature must appear in a document thatclaims conformance with that profile;

• if the value of thevalue attributeisprohibited, then the feature must not appear in a document thatclaims conformance with that profile;

• if the value attribute is not specified, then the feature specificationmust be interpreted as if the valueoptional were specified;

The valueuse of thevalue attribute isdeprecated. If itappears in a profile specification, then it must be interpreted as ifrequiredhad been specified.

If some defined (i.e., standardized) or otherwise well known feature is not specified byattp:feature element in a content profile, then it must be interpreted as if the feature were specifiedwith thevalue attribute equal tooptional. However, if not specified in a processor profile, no claimabout support or absence of support for the feature is implied.

If adocument instance makes use of a feature defined byE.1 Feature Designations and if the intended use of thedocument requires the recognition and processing of that feature, thenthe document must include arequired feature specification in one of its declared orreferenced profiles.

Thettp:feature element is illustrated by the following example.

<ttp:profile use="http://www.w3.org/ns/ttml/profile/ttml2-presentation">  <ttp:features xml:base="http://www.w3.org/ns/ttml/feature/"><ttp:feature value="required">#fontStyle-italic</ttp:feature><ttp:feature value="required">#textDecoration-under</ttp:feature><ttp:feature value="prohibited">#textOutline-blurred</ttp:feature>  </ttp:features></ttp:profile>

6.1.4 ttp:extensions

Thettp:extensions element is a container element used to groupinformation about extension support and usage requirements.

Thettp:extensions element accepts as its children zero or moreelements in theMetadata.class element group, followed byzero or morettp:extension elements.

<ttp:extensionsxml:base =<uri> :TT Extension Namespacexml:id = IDContent:Metadata.class*,ttp:extension*</ttp:extensions>

If specified, thexml:baseattribute must (1) adhere to the<uri> value syntax, (2) express an absolute URI thatadheres to[XML Base] and,(3) express an extension namespace as defined byF.1 Extension Designations. If not specified, thexml:base attribute's defaultvalue applies, which is the TT Extension Namespace.

Thexml:base attribute isused to permit the abbreviation of feature designation URIs expressedby childttp:extension elements.

6.1.5 ttp:extension

Thettp:extension element is used to specifyinformation about support and usage requirements for a particular extension.

<ttp:extension  extends =xsd:string  restricts =xsd:string  value = ("optional" |"required" |"use" |"prohibited") :see prose belowxml:id = IDContent: #PCDATA</ttp:extension>

The children of thettp:extension element must express a non-emptysequence ofcharacter information items the concatenation of which adheres to the<uri> value syntax.

If specified, theextends attribute and/or therestrictsattribute must (1) adhere to the<uri> value syntax, and(2) express a feature designation or extension designation as defined byE.1 Feature Designations orF.1 Extension Designations, respectively.

Theextends attribute may be used to indicate that the extension being definedis, from either (or both) a syntactic or (and) semantic perspective, a proper superset of thefeature or extension referenced by theextends attribute.Therestricts attribute may be used to indicate that the extension being definedis, from either (or both) a syntactic or (and) semantic perspective, a proper subset of thefeature or extension referenced by therestricts attribute.If anextends attribute is specified, then arestricts attribute mustnot be specified on attp:extension element; likewise, if arestricts attributeis specified, then anextends attribute must not be specified.

If the URI expressed by (1) the content of thettp:extensionelement, (2) theextends attribute, or (3) therestricts attributeis a relative URI, then, when combined with theextension namespace value expressed by thexml:base attribute of thenearest ancestorttp:extensions element, it must express anabsolute URI. In either case (original absolute URI or resultingabsolutized URI), the URI expressed by thettp:extensionelement must further adhere to the syntax of an extension designation asdefined byF.1 Extension Designations,while the URI expressed by theextends attribute and/or therestricts attribute must adhere to the syntax of a feature designationor an extension designation as defined byE.1 Feature Designations orF.1 Extension Designations, respectively.

If the URI expressed by the content of thettp:extension element,by theextends attribute, or by therestricts attributeis a relative URI, then anxml:base attribute should bespecified on the nearest ancestorttp:extensions element.

Thevalue attribute specifies constraints on support for or use ofthe designated extension according to the profile type.

If the profile is aprocessor profilethen the following semantics apply:

• if the value of thevalue attributeisoptional, then a processor may but neednot implement or otherwise support the extension in order to process the document;

• if the value isrequired, then perform the following steps:

  1. if the extension is implemented or otherwise supported by a processor, then continue processingthe document;

  2. otherwise, if(1) theextends attribute is specified on thisttp:extension element,(2) the value of theextends attribute designates an extension that is implemented or otherwise supported bya processor, and(3) the computed value of thettp:permitFeatureNarrowingproperty of the roottt element is notfalse,then continue processing the document;

  3. otherwise, if(1) therestricts attribute is specified on thisttp:extension element,(2) the value of therestricts attribute designates an extension that is implemented or otherwise supported bya processor, and(3) the computed value of thettp:permitFeatureWideningproperty of the roottt element is notfalse,then continue processing the document;

  4. otherwise, abort processing the document unless overridden by the end-user or some implementation specific parametertraceable to an end-user or to a user or system configuration setting.

• if the value attribute is not specified, then the extension specificationmust be interpreted as if the valuerequired were specified;

If the profile is acontent profilethen the following semantics apply:

• if the value of thevalue attributeisoptional, then the extension may but need not appear in a document thatclaims conformance with that profile;

• if the value of thevalue attributeisrequired, then the extension must appear in a document thatclaims conformance with that profile;

• if the value of thevalue attributeisprohibited, then the extension must not appear in a document thatclaims conformance with that profile;

• if the value attribute is not specified, then the extension specificationmust be interpreted as if the valueoptional were specified;

The valueuse of thevalue attribute isdeprecated. If itappears in a profile specification, then it must be interpreted as ifrequiredhad been specified.

If some well known extension is not specified byattp:extension element in a content profile, then it must be interpreted as if the extension were specifiedwith thevalue attribute equal tooptional. However, if not specified in a processor profile, no claimabout support or absence of support for the extension is implied.

If adocument instance makes useof an extension designatable byF.1 Extension Designations and if the intended use of the documentrequires the recognition and processing of that extension, then thedocument must include arequired extension specificationin one of its declared or referenced profiles.

Thettp:extension element is illustrated by the following example.

<ttp:profile use="http://www.w3.org/ns/ttml/profile/ttml2-transformation">  <ttp:extensions xml:base="http://example.org/ttml/extension/"><ttp:extension value="use">#prefilter-by-language</ttp:extension>  </ttp:extensions></ttp:profile>

6.2.1 ttp:contentProfiles

Thettp:contentProfiles attribute may be used by a content authorto express one or morecontent profiles ofthe Timed Text Markup Language (TTML) where theenclosing document instance claims conformance toall of a set ofspecifiedcontent profiles.

If specified, the value of this attribute must adhere to the following syntax,where eachprofile-designator item adheres to the<uri> value syntax, and,further, adheres to constraints defined on a profile designator in accordance with5.2 Profiling.

ttp:contentProfiles  : designators  | "all("<lwsp> designators<lwsp> ")"designators  : designator (<lwsp> designator)*designator  :<profile-designator>

If the list of designators is enclosed in the function syntaxall(...) or no function syntax is used,then conformance is claimed with all designatedcontent profiles.

If multiple designators are specified, then the absolutized form of each designator must be distinct; that is,after converting to absolutized form, duplicate designators are not permitted.

Attp:contentProfilesattribute is considered to be significant only when specified on thett element.

6.2.2 ttp:contentProfileCombination

Thettp:contentProfileCombination attribute is used to specify themethod for combining multiplecontent profiles.

If specified, the value of this attribute must adhere to the following syntax:

ttp:contentProfileCombination  : "leastRestrictive"  | "mostRestrictive"  | "replace"  | "ignore"

If not specified, the value of this parameter must be considered to beignore.

Given two ordered profile specification values,arg1 andarg2, and a content profile combination method,Table 6-1 – Content Profile Combination specifies the result of combining the two specification values, where the orderof arguments is determined in accordance with the lexical order ofcontent profiles in adocument instance.

Attp:contentProfileCombination attribute is considered to be significant onlywhen specified on thett element.

6.2.3 ttp:inferProcessorProfileMethod

Thettp:inferProcessorProfileMethod attribute is used to specify themethod for mapping a content profile specification value to a corresponding processorprofile specification value.

If specified, the value of this attribute must adhere to the following syntax:

ttp:inferProcessorProfileMethod  : "loose"  | "strict"

If this parameter's value isloose, then, when inferring a processor profile specification from a content profile specification,a loose (liberal) mapping applies.

If this parameter's value isstrict, then, when inferring a processor profile specification from a content profile specification,a strict (conservative) mapping applies.

If not specified, the value of this parameter must be consideredto beloose.

Given an input content profile specification value,input, and an infer processor profile method,Table 6-2 – Infer Processor Profile Method specifies the result of mapping the input specification value.

Attp:inferProcessorProfileMethod attribute is considered to be significant onlywhen specified on thett element.

6.2.4 ttp:inferProcessorProfileSource

Thettp:inferProcessorProfileSource attribute is used to specify thesource for mapping a content profile specification value to a corresponding processorprofile specification value.

If specified, the value of this attribute must adhere to the following syntax:

ttp:inferProcessorProfileSource  : "combined"  | "first"

If this parameter's value iscombined, then, when inferring a processor profile, the combined profile specificationset of theeffective content profile is used as the source of inference.

If this parameter's value isfirst, then, when inferring a processor profile, the first constituent profile ofthe combined profile specification set of theeffective content profile,where the processor profile inferred from that constituent profile is supported by thecontent processor,is used as the source of inference, about which see theconstruct inferred processor profile procedure for further details.

If not specified, the value of this parameter must be consideredto befirst.

Attp:inferProcessorProfileSource attribute is considered to be significant onlywhen specified on thett element.

6.2.5 ttp:permitFeatureNarrowing

Thettp:permitFeatureNarrowing attribute is used to specify whetherrequirements related to a feature or extension may be satisfied by a (syntactically or semantically) narrower interpretationof the feature or extension.

If specified, the value of this attribute must adhere to the following syntax:

ttp:permitFeatureNarrowing  :xsd:boolean                             // see[XML Schema Part 2], §3.2.2

If this parameter's value istrue, then, a requirement for support of a feature or extension may be satisfiedif the definition of the feature or extension specifies anextends attribute, and the feature or extension referencedby that attribute is supported by a processor.

If this parameter's value isfalse, then, a requirement for support of a feature or extension can not be satisfiedby a more narrowly defined feature or extension specified by anextends attribute.

If not specified, the value of this parameter must be consideredto befalse.

Attp:permitFeatureNarrowing attribute is considered to be significant onlywhen specified on thett element.

6.2.6 ttp:permitFeatureWidening

Thettp:permitFeatureWidening attribute is used to specify whetherrequirements related to a feature or extension may be satisfied by a (syntactically or semantically) wider interpretationof the feature or extension.

If specified, the value of this attribute must adhere to the following syntax:

ttp:permitFeatureWidening  :xsd:boolean                             // see[XML Schema Part 2], §3.2.2

If this parameter's value istrue, then, a requirement for support of a feature or extension may be satisfiedif the definition of the feature or extension specifies arestricts attribute, and the feature or extension referencedby that attribute is supported by a processor.

If this parameter's value isfalse, then, a requirement for support of a feature or extension can not be satisfiedby a more widely defined feature or extension specified by arestricts attribute.

If not specified, the value of this parameter must be consideredto befalse.

Attp:permitFeatureWidening attribute is considered to be significant onlywhen specified on thett element.

6.2.7 ttp:profile

Thettp:profile attributedenotes aprocessor profileof the Timed Text Markup Language (TTML) that applies when processingadocument instance.

If specified, the value of this attribute must adhere to the following syntaxwhere thedesignator adheres to the<uri> value syntax, and, further, must specify aprofile designator in accordance with5.2 Profiling.

ttp:profile  : designatordesignator  :<profile-designator>

Attp:profileattribute is considered to be significant only when specified on thett element.

If atop-levelprocessor profileis defined in adocument instance, then thettp:profileattribute should not be specified on thett element.

6.2.8 ttp:processorProfiles

Thettp:processorProfiles attribute may be used by a content authorto express one or moreprocessor profiles ofthe Timed Text Markup Language (TTML) where theenclosing document instance requires support for (1)all of a set ofspecifiedprocessor profiles or (2)any one of a set ofspecifiedprocessor profiles.

If specified, the value of this attribute must adhere to the following syntax,where eachprofile-designator item adheres to the<uri> value syntax, and,further, adheres to constraints defined on a profile designator in accordance with5.2 Profiling.

ttp:processorProfiles  : designators  | "all("<lwsp> designators<lwsp> ")"  | "any("<lwsp> designators<lwsp> ")"designators  : designator (<lwsp> designator)*designator  :<profile-designator>

If the list of designators is enclosed in the function syntaxall(...) or no function syntax is used,then support is required for all designatedprocessor profiles. If the listof designators is enclosed in the function syntaxany(...), then support is required for at least oneof the designatedprocessor profiles.

If multiple designators are specified, then the absolutized form of each designator must be distinct; that is,after converting to absolutized form, duplicate designators are not permitted.

Attp:processorProfilesattribute is considered to be significant only when specified on thett element.

6.2.9 ttp:processorProfileCombination

Thettp:processorProfileCombination attribute is used to specify themethod for combining multipleprocessor profiles.

If specified, the value of this attribute must adhere to the following syntax:

ttp:processorProfileCombination  : "leastRestrictive"  | "mostRestrictive"  | "replace"  | "ignore"

If not specified, the value of this parameter must be considered to beignore.

Given two ordered profile specification values,arg1 andarg2, and a processor profile combination method,Table 6-3 – Processor Profile Combination specifies the result of combining the two specification values, where the orderof arguments is determined in accordance with the lexical order ofprocessor profiles in adocument instance.

Attp:processorProfileCombination attribute is considered to be significant onlywhen specified on thett element.

6.2.10 ttp:validation

Thettp:validation attribute is used to specify whethervalidation processingmay or must be performed on adocument instance by avalidating content processor.

If specified, the value of this attribute must adhere to the following syntax:

ttp:validation  : "required"  | "optional"  | "prohibited"

If this parameter's value isrequired, then, avalidating content processormust performvalidation processing on a TTMLdocument instance prior to performingother types of processing, e.g., presentation or transformation processing.

If this parameter's value isoptional, then, avalidating content processormay, but need not, performvalidation processing on a TTMLdocument instance prior to performingother types of processing, e.g., presentation or transformation processing.

If this parameter's value isprohibited, then, avalidating content processormust not performvalidation processing on a TTMLdocument instance prior to performingother types of processing, e.g., presentation or transformation processing, unless the end-user or application overrides this prohibition.

Ifvalidation processing is performed on a TTMLdocument instance and validation fails, then the computed value ofthettp:validationAction property is used to determine what action to take before performing further processing.

If not specified, the value of this parameter must be consideredto beoptional.

Attp:validation attribute is considered to be significant onlywhen specified on thett element.

6.2.11 ttp:validationAction

Thettp:validationAction attribute is used to specify what action is to be takenby avalidating content processor whenvalidation of adocument instance fails.

If specified, the value of this attribute must adhere to the following syntax:

ttp:validationAction  : "abort"  | "warn"  | "ignore"

If this parameter's value isabort, then, unless abort processing is overridden by the end-user or application,avalidating content processormust abort processing of a TTMLdocument instance when avalidation error exception occurs.

If this parameter's value iswarn, then, avalidating content processorshould warn the end-user when avalidation error orvalidation warning exception occursand give the end-user the option to continue or abort processing.

If this parameter's value isignore, then, avalidating content processorshould not abort and should not warn the end-user when avalidation exceptionoccurs.

If not specified, the value of this parameter is determined as follows:if the computed value of thettp:validation property isrequired,then the value must be considered to beabort;if it isoptional,then the value must be considered to bewarn;otherwise, if it isprohibited,then the value must be considered to beignore.

Attp:validationAction attribute is considered to be significant onlywhen specified on thett element.

7.2.1 ttp:cellResolution

Thettp:cellResolution attribute may be used by an authorto express the number of horizontal and vertical cells into which theroot container regionarea is divided for the purpose of expressing presentation semantics in terms ofa uniform grid.

If specified, the value of this attribute must adhere to the following syntax:

ttp:cellResolution  : columns<lwsp> rows                     //columns != 0;rows != 0columns | rows  :<digit>+

If not specified, the number of columns and rows must be consideredto be 32 and 15, respectively. If specified, then columns or rows must not be zero (0).

Attp:cellResolution attribute is considered to be significant onlywhen specified on thett element.

Except where indicated otherwise, when a<length> expressed incells denotes a dimension parallel to the inline or block progression dimension,the cell's dimension in the inline or block progression dimension applies, respectively.

7.2.2 ttp:clockMode

Thettp:clockMode attribute is used to specify theinterpretation of time expressions as real-time time coordinates whenoperating with time base ofclock as defined by7.2.11 ttp:timeBase.

If specified, the value of this attribute must adhere to the following syntax:

ttp:clockMode  : "local"  | "gps"  | "utc"

If the time base, defined by7.2.11 ttp:timeBase, is designated asclock, then this parameter applies as follows: if theparameter's value islocal, then time expressions areinterpreted as local wall-clock time (and date) coordinates;ifutc, then time expressions areinterpreted as UTC time coordinates[UTC];ifgps, then time expressions areinterpreted as GPS time coordinates[GPS].

If not specified, the value of this parameter must be consideredto beutc.

Attp:clockMode attribute is considered to be significant onlywhen specified on thett element.

7.2.3 ttp:displayAspectRatio

Thettp:displayAspectRatio attribute is used to specify thedisplay aspect ratio of theroot container region as elaborated inH Root Container Region Semantics.

If specified, the value of this attribute must adhere to the following syntax:

ttp:displayAspectRatio  : numerator<lwsp> denominator            //numerator != 0;denominator != 0numerator | denominator  :<digit>+

If specified, then both numerator and denominator must be non-zero. If not specified, then the display aspect ratio oftheroot container region is determined byH Root Container Region Semantics.

Attp:displayAspectRatio attribute is considered to be significant onlywhen specified on thett element.

7.2.4 ttp:dropMode

Thettp:dropMode attribute is used to specifyconstraints on the interpretation and use of frame countsthat correspond with[SMPTE ST 12-1] time coordinates when operatingwith time base ofsmpte as defined by7.2.11 ttp:timeBase.

If specified, the value of this attribute must adhere to the following syntax:

ttp:dropMode  : "dropNTSC"  | "dropPAL"  | "nonDrop"

If the time base, defined by7.2.11 ttp:timeBase, is designated assmpte, then this parameter applies as follows: if theparameter's value isnonDrop, then, within any givensecond of a time expression, frames count from 0 toN−1, whereN is the value specified bythettp:frameRate parameter, but while ignoring any valuespecified by thettp:frameRateMultiplier parameter.

If this parameter's value isdropNTSC, then, within anygiven second of a time expression except the second00,frames count from 0 toN−1, whereN isthe value specified by thettp:frameRate parameter, butwhile ignoring any value specified by thettp:frameRateMultiplier parameter. If the second of a timeexpression is00 and the minute of the time expression isnot00,10,20,30,40, or50, then frame codes00and01 are dropped during that second; otherwise, theseframe codes are not dropped.

If this parameter's value isdropPAL, then, within anygiven second of a time expression except the second00,frames count from 0 toN−1, whereN isthe value specified by thettp:frameRate parameter, butwhile ignoring any value specified by thettp:frameRateMultiplier parameter. If the second of a timeexpression is00 and the minute of the time expression iseven but not00,20, or40,then frame codes00 through03 are droppedduring that second; otherwise, these frame codes are not dropped.

If not specified, thennonDrop must be assumed to apply.

Attp:dropMode attribute is considered to be significant onlywhen specified on thett element.

7.2.5 ttp:frameRate

Thettp:frameRate attribute is used to specify the frame rate of a relatedmedia object or the intrinsic frame rate of adocument instance in case it is intendedto function as an independent media object.

If specified, the value of this attribute must adhere to the following syntax:

ttp:frameRate  :<digit>+                                //value > 0

The frame rate that applies to adocument instance is used tointerpret time expressions that are expressed inframesas defined by12.3.1 <time-expression>.

If themedia time base applies and the effective frame rate isintegral, then a frame is interpreted as a division of a second of mediatime, such that if the frame rate is specified asF, thena second of media time is divided intoF intervals ofequal duration, where each interval is labeled as framef,withf ∈ [0…F−1].

If not specified, the frame rate must be considered to be equal to someapplication defined frame rate, or if no application defined frame rate applies,then thirty (30) frames per second. If specified, then the frame rate mustbe greater than zero (0).

Attp:frameRate attribute is considered to be significant onlywhen specified on thett element.

7.2.6 ttp:frameRateMultiplier

Thettp:frameRateMultiplier attribute is used tospecify a multiplier to be applied to the frame rate specified by attp:frameRate attribute in order to compute the effectiveframe rate.

If specified, the value of this attribute must adhere to the following syntax:

ttp:frameRateMultiplier  : numerator<lwsp> denominator            //numerator != 0;denominator != 0numerator | denominator  :<digit>+

A frame rate multiplier is used when the desired frame rate cannotbe expressed as an integral number of frames per second.

If not specified, the frame rate multiplier must be considered to be equal to some application defined frame rate multiplier,or if no application defined frame rate multiplier applies, then one (1:1). Both numerator and denominator must be non-zero.

Attp:frameRateMultiplier attribute is considered to be significant onlywhen specified on thett element.

7.2.7 ttp:markerMode

Thettp:markerMode attribute is used to specifyconstraints on the interpretation and use of time expressionsthat correspond with[SMPTE ST 12-1] time coordinates when operatingwith time base ofsmpte as defined by7.2.11 ttp:timeBase.

If specified, the value of this attribute must adhere to the following syntax:

ttp:markerMode  : "continuous"  | "discontinuous"

If the time base, defined by7.2.11 ttp:timeBase, is designated assmpte, then this parameter applies as follows: if theparameter's value iscontinuous, then[SMPTE ST 12-1] time coordinatesmay be assumed to be linear and either monotonically increasing ordecreasing; however, ifdiscontinuous, then any assumptionmust not be made regarding linearity or monotonicity of time coordinates.

If not specified, the value of this parameter must be consideredto bediscontinuous.

Attp:markerMode attribute is considered to be significant onlywhen specified on thett element.

If a value ofcontinuous applies, then timeexpressions may be converted to real timecoordinates by taking into account the computed frame rateand drop mode as expressed by thettp:dropMode parameter.In this case, thecontent processor must create and maintain asynthetic smpte document syncbase within which these timeexpressions are interpreted as further described in12.4 Timing Semantics.

If a value ofdiscontinuous applies, then timeexpressions must not be converted to real timecoordinates, arithmetical operators (addition, multiplication) are notdefined on time expressions, and, consequently, any (well-formed)expression of a duration must be considered to be invalid.

7.2.8 ttp:pixelAspectRatio

Thettp:pixelAspectRatio attribute is used to specify thepixel aspect ratio of theroot container region as elaborated inH Root Container Region Semantics

If specified, the value of this attribute must adhere to the following syntax:

ttp:pixelAspectRatio  : numerator<lwsp> denominator            //numerator != 0;denominator != 0numerator | denominator  :<digit>+

If specified, then both numerator and denominator must be non-zero. If not specified, then the pixel aspect ratio oftheroot container region is determined byH Root Container Region Semantics.

Attp:pixelAspectRatio attribute is considered to be significant onlywhen specified on thett element.

Thettp:pixelAspectRatio attribute should not be specifiedunless atts:extent attribute consistingof two<length> specifications usingpx (pixel) units is alsospecified on thett element,without which the use of attp:pixelAspectRatio attribute is deprecated.

7.2.9 ttp:subFrameRate

Thettp:subFrameRate attribute is used to specify the sub-frame rate of a relatedmedia object or the intrinsic sub-frame rate of adocument instance in case it is intendedto function as an independent media object.

If specified, the value of this attribute must adhere to the following syntax:

ttp:subFrameRate  :<digit>+                                //value > 0

The sub-frame rate that applies to adocument instance is used tointerpret time expressions that are expressed insub-framesas defined by12.3.1 <time-expression>.

If themedia time base applies and the effective frame rate isintegral, a sub-frame is interpreted as a division of a frame of mediatime, such that if the sub-frame rate is specified asS, thena frame of media time is divided intoS intervals ofequal duration, where each interval is labeled as sub-frames,withs ∈ [0…S−1].

If not specified, the sub-frame rate must be considered to be equal to some application defined sub-frame rate, or if no application definedsub-frame rate applies, then one (1). If specified, then the sub-frame rate must be greater than zero (0).

Attp:subFrameRate attribute is considered to be significant onlywhen specified on thett element.

7.2.10 ttp:tickRate

Thettp:tickRate attribute is used to specify the tick rate of a relatedmedia object or the intrinsic tick rate of content of adocument instance in case it is intendedto function as an independent media object.

If specified, the value of this attribute must adhere to the following syntax:

ttp:tickRate  :<digit>+                                //value > 0

The tick rate that applies to adocument instance is used tointerpret time expressions that are expressed inticks byusing thet metric as defined by12.3.1 <time-expression>.

If themedia time base applies,a tick is interpreted as an integral division of a second of mediatime, such that if the tick rate is specified asT, thena second of media time is divided intoT intervals ofequal duration, where each interval is labeled as tickt,witht ∈ [0…T−1].

If not specified, then if a frame rate is specified, the tick ratemust be considered to be the effective frame rate multiplied by thesub-frame rate (i.e., ticks are interpreted as sub-frames); or, if noframe rate is specified, the tick rate must be considered to be one (1)tick per second of media time. If specified, then the tick ratemust not be zero (0).

Attp:tickRate attribute is considered to be significant onlywhen specified on thett element.

7.2.11 ttp:timeBase

Thettp:timeBase attribute is used to specify thedocument temporal coordinate space.

If specified, the value of this attribute must adhere to the following syntax:

ttp:timeBase  : "media"  | "smpte"  | "clock"

If the time base is designated asmedia, then a timeexpression denotes a coordinate in some media object's time line,where the media object may be an external media object with which thecontent of adocument instance is to be synchronized, or it maybe the content of adocument instance itself in a case wherethe timed text content is intended to establish an independent timeline.

If the time base is designated assmpte,then a time expression denotes a[SMPTE ST 12-1] timecoordinate with which the content of adocument instance is tobe synchronized. In this case, the value of thettp:markerModeandttp:dropMode parameters apply, as defined by7.2.7 ttp:markerMode and7.2.4 ttp:dropMode, respectively.

If the time base is designated asclock, then the timeexpression denotes a coordinate in some real-world time line asestablished by some real-time clock, such as the local wall-clock timeor UTC (Coordinated Universal Time) or GPS (Global Positioning System)time lines.

If not specified, the default time base must be considered to bemedia.

Attp:timeBase attribute is considered to be significant onlywhen specified on thett element.

When operating with eithermedia orsmptetime bases, a diachronic presentation of adocument instance maybe subject to transformations of the controlling time line, such astemporal reversal, dilation (expansion), or constriction(compression); however, when operating with theclocktime base, no transformations are permitted, and diachronicpresentation proceeds on a linear, monotonically increasing time linebased on the passage of real time.

Note:

The sub-sections of this section are ordered logically (from highest to lowest level construct).

8.1.1 tt

Thett element serves as the root document element of adocument instance.

Thett element accepts as its children zero or onehead element followed byzero or onebody element.

<tttts:extent =xsd:stringxml:base =<uri>xml:id = IDxml:lang =xsd:stringxml:space = ("default" |"preserve") : default  {any attributes in TT Parameter Namespace}Content:head?,body?</tt>

Theroot temporal extent, i.e., the time interval over which adocument instance is active, has an implicit duration that is equal to theimplicit duration of thebody element of the document, if thebody element is present, or zero, if thebody element is absent.

If thetts:extent attribute is specified on thettelement, then it must adhere to10.2.16 tts:extent, in which case itspecifies thespatial extent of theroot container region inwhichcontent regions are located and presented. If notts:extentattribute is specified, then thespatial extent of theroot container region is determined by rules specified inH Root Container Region Semantics.The origin of theroot container region is determined by thedocument processing context.

Anxml:lang attribute must be specified on thett element.If the attribute value is empty, it signifies that there is no default language that appliesto the text contained within thedocument instance.

If noxml:space attribute is specified upon thett element, then it mustbe considered as if the attribute had been specified with a value ofdefault.

8.1.2 head

Thehead element is a container element used to group header matter, including metadata,profile, embedded content resources, styling, and layout information.

Thehead element accepts as its children zero or moreelements in theMetadata.class element group,followed by zero or more elements in theProfile.class element group,followed by zero or oneresources element,followed by zero or onestyling element,followed by zero or onelayout element,followed by zero or oneanimation element.

Any metadata specified by children in theMetadata.classelement group applies semantically to thedocument instance as awhole, and not just thehead element.

Any parameters specified by children in theParameters.classelement group applies semantically to thedocument instance as awhole, and not just thehead element.

Aresources child element is used to specify embedded content constructsthat are referenced from certain style constructs andembedded content elements.

Astyling child element is used to specify style constructsthat are referenced from other style constructs, by layout constructs, and bycontent elements.

Alayout child element is used to specify layout constructs thatare referenced bycontent elements.

Ananimation child element is used to specify animation constructs thattarget animatablecontent elementorLayout elements.

<headxml:base =<uri>xml:id = IDxml:lang =xsd:stringxml:space = ("default" |"preserve")Content:Metadata.class*,Profile.class*,resources?,styling?,layout?,animation?</head>

To the extent that time semantics apply to the content of thehead element, the implied time interval of this element isdefined to be coterminous with theroot temporal extent.

8.1.3 body

Thebody element functions as a logical container and a temporalstructuring element for a sequence of textual content units represented aslogical divisions.

Thebody element accepts as its children zero or moreelements in theMetadata.class element group,followed by zero or moreelements in theAnimation.class element group,followed byzero or morediv elements.

Any metadata specified by children in theMetadata.classelement group applies semantically to thebody element and its descendants as a whole.

Any animation elements specified by children in theAnimation.classelement group apply semantically to thebody element.

<bodyanimate = IDREFSbegin =<time-expression>condition =<condition>dur =<time-expression>end =<time-expression>region = IDREFstyle = IDREFStimeContainer = ("par" |"seq")xml:base =<uri>xml:id = IDxml:lang =xsd:stringxml:space = ("default" |"preserve")  {any attributes in TT Metadata Namespace}  {any attributes inTT Style Namespaces}Content:Metadata.class*,Animation.class*,div*</body>

An author may specify a temporal interval for abody element usingthebegin,dur, andend attributes. If the begin pointof this interval remains unspecified, then the begin point is interpreted as the later of the beginningpoint of thedocument temporal coordinate spaceand the beginning point of theroot temporal extent.If the end point of this interval remains unspecified, then theend point is interpreted as the ending point of theroot temporal extent.

If relative begin or end times are specified on thebodyelement, then these times are resolved by reference to the beginningof thedocument temporal coordinate space.

If theroot temporal extent is shorter than the computed duration of thebody element, then the active time interval of abody element istruncated to the active end point of theroot temporal extent.

An author may associate a set of style properties with abody element by means of either thestyleattribute or inline style attributes or a combination thereof.

If notimeContainer attribute is specified on abody element, then it must be interpreted as havingparalleltime containment semantics.

8.1.4 div

Thediv element functions as a logical container and a temporalstructuring element for a sequence of textual content units represented aslogical sub-divisions or paragraphs.

Thediv element accepts as its children zero or moreelements in theMetadata.class element group,followed by zero or moreelements in theAnimation.class element group,followed by zero or oneelement in theLayout.class element group,followed by zero or more elements in theBlock.class orEmbedded.class element groups.

Any metadata specified by children in theMetadata.classelement group applies semantically to thediv element and its descendants as a whole.

Any animation elements specified by children in theAnimation.classelement group apply semantically to thediv element.

<divanimate = IDREFSbegin =<time-expression>condition =<condition>dur =<time-expression>end =<time-expression>region = IDREFstyle = IDREFStimeContainer = ("par" |"seq")xml:base =<uri>xml:id = IDxml:lang =xsd:stringxml:space = ("default" |"preserve")  {any attributes in TT Metadata Namespace}  {any attributes inTT Style Namespaces}Content:Metadata.class*,Animation.class*,Layout.class?, (Block.class|Embedded.class)*</div>

An author may associate a set of style properties with adiv element by means of eitherthestyle attribute or inline style attributes or a combination thereof.

If notimeContainer attribute is specified onadiv element, then it must be interpreted as havingparallel time containment semantics.

8.1.5 p

Ap element represents a logical paragraph, serving asa transition between block level and inline level formatting semantics.

Thep element accepts as its children zero or moreelements in theMetadata.class element group,followed by zero or moreelements in theAnimation.class element group,followed by zero or oneelement in theLayout.class element group,followed by zero or more elements in theInline.class orEmbedded.class element groups.

Any metadata specified by children in theMetadata.classelement group applies semantically to thep element and its descendants as a whole.

Any animation elements specified by children in theAnimation.classelement group apply semantically to thep element.

<panimate = IDREFSbegin =<time-expression>condition =<condition>dur =<time-expression>end =<time-expression>region = IDREFstyle = IDREFStimeContainer = ("par" |"seq")xml:base =<uri>xml:id = IDxml:lang =xsd:stringxml:space = ("default" |"preserve")  {any attributes in TT Metadata Namespace}  {any attributes inTT Style Namespaces}Content:Metadata.class*,Animation.class*,Layout.class?, (Inline.class|Embedded.class)*</p>

An author may associate a set of style properties with ap element by means of either thestyleattribute or inline style attributes or a combination thereof.

If notimeContainer attribute is specified onap element, then it must be interpreted as havingparallel time containment semantics.

If a sequence of children of ap elementconsists solely ofcharacter information items, then that sequence mustbe considered to be ananonymous span for the purpose ofapplying style properties that apply tospan elements, for details about which, see the[construct anonymous spans] procedure.

8.1.6 span

Thespan element functions as a logical container and a temporalstructuring element for a sequence of textual content units having inlinelevel formatting semantics.

When presented on a visual medium, aspan element is intended togenerate a sequence of inline areas, each containing one or moreglyph area.

Thespan element accepts as its children zero or moreelements in theMetadata.class element group,followed by zero or moreelements in theAnimation.class element group,followed by zero or more elements in theInline.class orEmbedded.class element groups.

Any metadata specified by children in theMetadata.classelement group applies semantically to thespan element and its descendants as a whole.

Any animation elements specified by children in theAnimation.classelement group apply semantically to thespan element.

<spananimate = IDREFSbegin =<time-expression>condition =<condition>dur =<time-expression>end =<time-expression>region = IDREFstyle = IDREFStimeContainer = ("par" |"seq")xlink:arcrole =<uri-list>xlink:href =<uri>xlink:role =<uri-list>xlink:show = ("new" |"replace" |"embed" |"other" |"none") : newxlink:title =xsd:stringxml:base =<uri>xml:id = IDxml:lang =xsd:stringxml:space = ("default" |"preserve")  {any attributes in TT Metadata Namespace}  {any attributes inTT Style Namespaces}Content:Metadata.class*,Animation.class*, (Inline.class|Embedded.class)*</span>

An author may associate a set of style properties with aspan element by means of either thestyleattribute or inline style attributes or a combination thereof.

If notimeContainer attribute is specified onaspan element, then it must be interpreted as havingparallel time containment semantics.

The linking attributesxlink:* may be used to link aspan element with related content, using thespecified location (href), roles, and title. The behavior of link activation is affected by thexlink:show attribute,the precise meaning of which is determined by thedocument processing context.

If aspan element specifies anxlink:href attribute, then a nestedspan element descendant must not specifyanxlink:href attribute, and, if it does, then the latter must be ignored for the purpose of presentation or activation processing.

If a sequence of children of aspan elementconsists solely ofcharacter information items, then that sequence mustbe considered to be ananonymous span for the purpose ofapplying style properties that apply tospan elements, for details about which, see the[construct anonymous spans] procedure.

8.1.7 br

Thebr element denotes an explicit line break.

Any metadata specified by children in theMetadata.classelement group applies semantically to thebr element and its descendants as a whole.

The use ofAnimation.class children is deprecated.

<brcondition =<condition>style = IDREFSxml:base =<uri>xml:id = IDxml:lang =xsd:stringxml:space = ("default" |"preserve")  {any attributes in TT Metadata Namespace}  {any attributes inTT Style Namespaces}Content:Metadata.class*,Animation.class*</br>

When presented on a visual medium, the presence of abr element must beinterpreted as a forced line break.

8.2.1 condition

Thecondition attribute is used toconditionally exclude an element(and its descendants) from semantic processing,in which case the element is referred to as aconditionalized element.

Thecondition attribute may be used with any element in the core vocabulary catalogexcept profile matter, i.e., elements of theProfile Module.

The value of acondition attribute must adhere to a<condition> expressionwhich is evaluated at the time of presentation processing (lazy evaluation)or prior to the time of presentation processing (eager evaluation), where eager evaluation may occur only when the value resultingfrom evaluation cannot change or is known to not change during presentation processing.

For the purpose of presentation processing, if an element specifies acondition attribute, andits<condition> expression value evaluates tofalse,then the semantics of the element and its descendant elementsmust be ignored unless those semantics are explicitly excepted,which is to say, the element and its descendant elements areconditionally excludedregardless of the evaluation of any<condition> expressionsspecified on those descendant elements.

Unless ahigher level protocol applies, the following exceptions apply for thepurpose of determining which semantics are to be ignored when a<condition> expressionvalue evaluates tofalse:

• thetiming semantics of atimed element are not ignored;

• thechained referential semantics of astyle element are not ignored;

8.2.2 xlink:arcrole

Thexlink:arcrole attribute is used as defined by[XLink 1.1].

Thexlink:arcrole attribute may be used with anyspan orimage element.

8.2.3 xlink:href

Thexlink:href attribute is used as defined by[XLink 1.1].

Thexlink:href attribute may be used with anyspan orimage element.

8.2.4 xlink:role

Thexlink:role attribute is used as defined by[XLink 1.1].

Thexlink:role attribute may be used with anyspan orimage element.

8.2.5 xlink:show

Thexlink:show attribute is used as defined by[XLink 1.1].

Thexlink:show attribute may be used with anyspan orimage element.

8.2.6 xlink:title

Thexlink:title attribute is used as defined by[XLink 1.1].

Thexlink:title attribute may be used with anyspan orimage element.

8.2.7 xml:base

Thexml:base attribute is used as defined by[XML Base].

Thexml:base attribute may be used with any element in the core vocabulary catalogthat admits (1) acondition attribute, (2) a descendantelement in theMetadata.class element group, or(3) a descendant element that admits anxml:base attribute.

8.2.8 xml:id

Thexml:id attribute is used as defined by[XML ID].

Thexml:id attribute may be used with any element in the core vocabulary catalog.

8.2.9 xml:lang

Thexml:lang attribute is used as defined by[XML 1.0], §2.12,Language Identification.

Thexml:lang attribute must be specified on thettelement and may be specified by an instance of any other element typein the core vocabulary catalog except parameter vocabulary.

The use ofxml:lang on content and metadata elements is illustrated by the following example.

<tt ...xml:lang="">...<pxml:lang="en">Jean said hello.</p><pxml:lang="fr">Jean dit bonjour.</p><p>  <image src="#talking-image">    <ttm:item name="altText"xml:lang="en">Talking</ttm:item>    <ttm:item name="altText"xml:lang="fr">Parlant</ttm:item>  </image></p>...</tt>

8.2.10 xml:space

Thexml:space attribute is used as defined by[XML 1.0], §2.10,White Space Handling.

Thexml:space attribute may be used with any element inthe core vocabulary catalog except parameter vocabulary.

The semantics of the valuedefault are fixed to mean thatwhen performing presentation processing of adocument instance asdescribed by11.3.1.4 Synchronic Flow Processing,processing must occur asif the following properties were specified on the affectedelements of an equivalent intermediate XSL-FO document:

• suppress-at-line-break="auto"

• linefeed-treatment="treat-as-space"

• white-space-collapse="true"

• white-space-treatment="ignore-if-surrounding-linefeed"

Similarly, the semantics of the valuepreserve are fixed to mean thatwhen performing presentation processing, processing must occur asif the following properties were specified on the affectedelements of an equivalent intermediate XSL-FO document:

• suppress-at-line-break="retain"

• linefeed-treatment="preserve"

• white-space-collapse="false"

• white-space-treatment="preserve"

If an unnormalized horizontal tab	 (HT) character appearsin acharacter information itemof areduced xml infoset, then, when presented visually, that tabcharacter is treated as if it were a single (SPACE) character.

When performing other types of processing intended to eventuallyresult in a visual presentation by means other than those describedin this specification, the semantics of space collapsing andpreservation as described above should be respected. For other typesof processing, the treatment of thexml:space attributeis processor dependent, but should respect the semantics describedabove if possible.

8.3.1 <absolute-profile-designator>

An <absolute-profile-designator> value expression is used to either (1) define the absolute designator associated witha locally defined profile or (2) refer to a remotely defined profile.

<absolute-profile-designator>  :<absolute-uri>

8.3.2 <absolute-uri>

An <absolute-uri> value expression is used to specify an absolute URI[URI].

<absolute-uri>  :<uri>                                     // absolute form only

In the context of an <absolute-uri> value expression, the value syntax of the<uri> expressionmust adhere to the absolute form of a URI as defined by[URI], §4.3.

8.3.3 <arguments>

A <arguments> value is a sub-expression used with afunction-expression non-terminal of an<expression> value.

<arguments>  : "("<lwsp>? ")"  | "("<lwsp>? argument-list<lwsp>? ")"argument-list  :<expression> (<lwsp>? ","<lwsp>?<expression>)*

8.3.4 <bound-parameter>

A <bound-parameter> value is one of an enumerated collection of named parameters bound to a value by thecontent processor.

<bound-parameter>  : "forced"  | "mediaAspectRatio"  | "mediaLanguage"  | "userLanguage"

forced

Evaluates to a boolean value that denotes whether thecontent processor is operating withforced subtitles enabled.If used in adocument instance, then ausesForcednamed metadata item should be specified as a child of thehead element.

mediaAspectRatio

Evaluates to a numeric value equal to the aspect ratio of therelated media object.

mediaLanguage

Evaluates to a string value equal to the (primary) language of therelated media object.

userLanguage

Evaluates to a string value equal to the (primary) language of the user as determined by thedocument processing context.

8.3.5 <condition>

A <condition> value is used to specify an expression that evaluates to a binary valuewhich is used to determine if the semantics of aconditionalized element is respected or ignored during content processing.

<condition>  :<expression>

Afunction-expression that appears in a <condition> value must take the formof a<condition-function> expression.

8.3.6 <condition-function>

A <condition-function> value is a sub-expression that may be used in a<condition> value expression.

<condition-function>  :<media-function>  |<parameter-function>  |<supports-function>

8.3.7 <expression>

An <expression> value is a sub-expression of a<condition> value.

<expression>  : logical-or-expressionlogical-or-expression  : logical-and-expression  | logical-or-expression<lwsp>? "||"<lwsp>? logical-and-expressionlogical-and-expression  : equality-expression  | logical-and-expression<lwsp>? "&&"<lwsp>? equality-expressionequality-expression  : relational-expression  | equality-expression<lwsp>? "=="<lwsp>? relational-expression  | equality-expression<lwsp>? "!="<lwsp>? relational-expressionrelational-expression  : additive-expression  | relational-expression<lwsp>? "<"<lwsp>? additive-expression  | relational-expression<lwsp>? ">"<lwsp>? additive-expression  | relational-expression<lwsp>? "<="<lwsp>? additive-expression  | relational-expression<lwsp>? ">="<lwsp>? additive-expressionadditive-expression  : multiplicitive-expression  | additive-expression<lwsp>? "+"<lwsp>? multiplicitive-expression  | additive-expression<lwsp>? "-"<lwsp>? multiplicitive-expressionmultiplicitive-expression  : unary-expression  | multiplicitive-expression<lwsp>? "*"<lwsp>? unary-expression  | multiplicitive-expression<lwsp>? "/"<lwsp>? unary-expression  | multiplicitive-expression<lwsp>? "%"<lwsp>? unary-expressionunary-expression  : primary-or-function-expression  | "+"<lwsp>? unary-expression  | "-"<lwsp>? unary-expression  | "!"<lwsp>? unary-expressionprimary-or-function-expression  : primary-expression  | function-expressionprimary-expression  : identifier  | literal  | "("<lwsp>? expression<lwsp>? ")"function-expression  : identifier<arguments>identifier  :xsd:NCNameliteral  : boolean-literal  | numeric-literal  | string-literalboolean-literal  : "true"  | "false"numeric-literal  : decimal-literaldecimal-literal  : decimal-integer-literal "." decimal-digits? exponent-part?  | decimal-integer-literal exponent-part?  | "." decimal-digits exponent-part?decimal-integer-literal  : "0"  | non-zero-digit decimal-digits?decimal-digits  : decimal-digit  | decimal-digits decimal-digitdecimal-digit  : "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"non-zero-digit  : "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"exponent-part  : exponent-indicator signed-integerexponent-indicator  : "e" | "E"signed-integer  : decimal-digits  | "+" decimal-digits  | "-" decimal-digitsstring-literal  :<quoted-string>

8.3.8 <fragment-profile-designator>

A <fragment-profile-designator> value expression is used to designate a local profile by reference.

<fragment-profile-designator>  :<fragment-uri>

8.3.9 <fragment-uri>

A <fragment-uri> value expression is used to specify a fragment URI[URI].

<fragment-uri>  :<uri>                                     // fragment component only

In the context of a <fragment-uri> value expression, the value syntax of the<uri> expressionmust adhere to the fragment component of a URI as defined by[URI], §3 and §3.5,i.e., the scheme, authority, path, and query components are empty (not specified), and only the fragment component is non-empty (specified).

8.3.10 <media-function>

A <media-function> value is a sub-expression that may be used in a<condition> value expressionin order to perform a media query on therelated media object or thedocument processing context.

<media-function>  : "media("<lwsp>? media-query<lwsp>? ")"media-query  :<quoted-string>

Themedia-query argument of a <media-function> value expression must adhere tothe syntax of themedia_query_list defined by[Media Queries], §3.

A <media-function> value expression evaluates totrue if the specified media queryevaluates totrue, otherwise, the value expression evaluates tofalse.

If the semantics of a <media-function> expression is not supported, then that expression mustevaluate tofalse.

8.3.11 <profile-designator>

A <profile-designator> value expression is used to designate a profile, either for the purpose of defining a profileor for the purpose of referencing a defined profile.

<profile-designator>  :<absolute-profile-designator>  |<relative-profile-designator>  |<fragment-profile-designator>

8.3.12 <parameter-function>

A <parameter-function> value is a sub-expression that may be used in a<condition> value expressionin order to obtain a named parameter of thedocument processing context.

<parameter-function>  : "parameter("<lwsp>? parameter-name<lwsp>? ")"parameter-name  :<quoted-string>

When de-quoted, theparameter-name argument of a <parameter-function> value expression must adhere to anxsd:NCName, which must, in turn, be one of the values enumeratedby<bound-parameter>.

A <parameter-function> value expression evaluates to the value associated with (bound to) thespecified parameter name.

8.3.13 <quoted-string>

A <quoted-string> value expression is used to specify a double or single quoted string.

<quoted-string>  : double-quoted-string  | single-quoted-stringdouble-quoted-string  : '"' ([^"\\] | escape)* '"'single-quoted-string  : "'" ([^'\\] | escape)* "'"escape  : '\\'char

8.3.14 <relative-profile-designator>

A <relative-profile-designator> value expression is used to refer to a standardized profile with respect tothe TT Profile Namespace, which serves as the base URI with which relative profile designators are absolutized.

<relative-profile-designator>  :<relative-uri>

8.3.15 <relative-uri>

A <relative-uri> value expression is used to specify a relative URI[URI].

<relative-uri>  :<uri>                                     // no scheme component present

In the context of a <relative-uri> value expression, the value syntax of the<uri> expressionmust adhere to the relative form of a URI as defined by[URI], §3,i.e., the scheme and authority components are empty (not specified), but the path, and, optionally, the query and fragment components are specified.

8.3.16 <supports-function>

A <supports-function> value is a sub-expression that may be used in a<condition> value expressionin order to obtain a boolean value that denotes whether a specifiedfeature orextensionis supported or not.

<supports-function>  : "supports("<lwsp>? feature-or-extension-designator<lwsp>? ")"feature-or-extension-designator  :<quoted-string>

Thefeature-or-extension-designator argument of a <supports-function> value expression must expressa feature designation or an extension designation as defined byE.1 Feature Designations andF.1 Extension Designations, respectively, and where thefeature-namespace orextension-namespace component of the designation is optional, and, ifnot specified, is considered to be equal to theTT Feature Namespace orTT Extension Namespace,respectively.

A <supports-function> value expression evaluates totrue if the specified feature or extensiondesignator is (semantically) supported by thecontent processor.

8.3.17 <uri>

A <uri> value expression is used to specify a URI[URI].

<uri>  :xsd:anyURI

The value syntax of thexsd:anyURI data type must adhere to the definition specified by[XML Schema Part 2], §3.2.17.

8.3.18 <uri-list>

A <uri-list> value expression is used to specify a non-empty list of URI[URI] expressions.

<uri-list>  :<uri> (<lwsp><uri>)*

9.1.1 audio

Theaudio element is used to define or refer to anaudio resource.

Anaudio element may appear in two contexts: (1) as a child of aresources element and(2) as a child of an element in theBlock.class element group, namely, as a child of adiv orp element, oras a child of aspan element. The former is referred to as anaudio defining context, the latter as anaudio presentation context.

When anaudio element appears in anaudio defining context, itserves as a sharable definition of anaudio resource that may be referenced by otheraudio elements in theenclosing document instance.

When anaudio element appears in anaudio presentation context, itserves as a non-sharable definition of anaudio resource that implies presentation (rendering) semantics, i.e., that it is intended to be played.

Theaudio element accepts as its childrenzero or more elements in theMetadata.class element group, followed byzero or more elements in theAnimation.class element group, followed by zero or moresource elements.

<audioanimate = IDREFSbegin =<time-expression>  clipBegin =<time-expression>  clipEnd =<time-expression>condition =<condition>dur =<time-expression>end =<time-expression>src =<audio>style = IDREFStimeContainer = ("par" |"seq")type =xsd:stringxml:base =<uri>xml:id = IDxml:lang =xsd:stringxml:space = ("default" |"preserve")  {any attributes inTT Style Namespaces}  {any attributes in TT Metadata Namespace}Content:Metadata.class*,Animation.class*,source*</audio>

Anaudio element designates anaudio resource by(1) referring to abuilt-in data resource,(2) referring to anexternal data resource, or(3) defining or referring to anembedded data resource,where thedata resource contains audio content.

If anaudio element specifies asrc attribute, then it must not specify achildsource element. Conversely,if anaudio element does not specify asrc attribute, then it must specify one or morechildsource elements.

If anaudio element specifies asrc attribute and its value does not refer to a fragment of theenclosing document instance, then it should specify atype attribute, in which case the value of thetype attribute must correspond with the media (content) typeof the referenced resource. Otherwise, atype attribute must not be specified.

If specified, the value of theclipBegin attribute must adhere to theoffset-time form of a12.3.1 <time-expression>, in which case, the value of this expression denotes a normal play time offset relative to thebeginning of the referenced audio content, and designates the point where audio presentation commences.If this specified value is greater than the intrinsic durationof the referenced audio content, then the resolved value ofclipBegin is considered to be the intrinsic duration.If noclipBegin attribute is specified, then a value of0 applies.

Similarly, if specified, the value of theclipEnd attribute must adhere to theoffset-time form of a12.3.1 <time-expression>, in which case, the value of this expression denotes a normal play time offset relative to thebeginning of the referenced audio content, and designates the point where presentation ceases.If this specified value is greater than the intrinsic durationof the referenced audio content, then the resolved value ofclipEnd is considered to be the intrinsic duration.If noclipEnd attribute is specified, then a value equal to the intrinsic duration of the audio content applies.

The use of theaudio element is illustrated by the following example.

...<audio src="http://example.com/audio/description.mp3" type="audio/mp3"/>...

9.1.2 chunk

Thechunk element is used to represent a distinct chunk (fragment) of data.

Achunk element may appear as a child of adata element.

<chunkcondition =<condition>encoding = ("base16" |"base32" |"base32hex" |"base64" |"base64url") : base64  length =xsd:nonNegativeIntegerxml:base =<uri>xml:id = IDContent: #PCDATA</chunk>

If anencoding attribute is specified, then it must denote the actual encoding of the byte sequence represented by thechunk element. If noencoding attribute is specified, then the encoding must be considered to bebase64.

If alength attribute is specified, then it must denote the number of decoded bytes in the byte sequence represented by thechunk element. When decoding, if a specified length value does not match the number of decoded bytes, then the chunk and its containerdataelement must return a zero length byte sequence.If nolength attribute is specified, then the chunk is considered to have a length equal to the actual number of decoded bytes.

The use of chunked data is illustrated by the following example.

...<data type="text/plain; charset=us-ascii" length="44">  <chunk length="19">    VGhlIHF1aWNrIGJyb3duIGZveA==  </chunk>  <chunk length="25">    IGp1bXBzIG92ZXIgdGhlIGxhenkgZG9nLg==  </chunk></data>...

9.1.3 data

Thedata element functions as a generic container for or reference to arbitrary data.

Adata element may appear in three contexts:(1) as a child of aresources element,referred to as adata defining context,(2) as a child of ametadata element,referred to as adata binding context for metadata, or(3) as a child of asource element,referred to as adata binding context for source,and where these latter two contexts are referred to collectively asdata binding contexts.

When adata element appears in adata defining context, itserves as a sharable definition of a data resource that may be referenced by thesrc attribute of(1) anotherdata element,(2) anembedded content element, or(3) asource element.In this case, the contextualized active time interval of thedata element is the intersection ofthe active time interval of its parentresources element andthe active time interval of its referring element.

When adata element appears in adata binding context, itserves as a non-sharable definition of a data resource that implies binding semantics, i.e., that it is intended to bound to (associated with) its immediate contextof reference. In this case, the active time interval of thedata element is the same as the active time interval of its closest ancestortimed element.

Thedata element accepts one of the following three content models:(1) one or more text nodes (i.e.,#PCDATA),(2) zero or more elements in theMetadata.class element group followed by one or morechunk elements, or(3) zero or more elements in theMetadata.class element group followed by one or moresource elements, wherethe first is referred to assimple data embedding,the second aschunked data embedding, andthe third assourced data embedding.

Whensimple data embedding is used, the data resource is obtained by decoding the#PCDATA content.Whenchunked data embedding is used, the data resource is obtained by concatenating the byte sequences obtained by decoding eachchildchunk element.Whensourced data embedding is used, the data resource is obtained from the first resolvablechildsource element. Furthermore,a childsource element must notcontain adata element, but may refer to adata element in adata defining context.

<datacondition =<condition>encoding = ("base16" |"base32" |"base32hex" |"base64" |"base64url") :see prose belowformat =<data-format>  length =xsd:nonNegativeIntegersrc =<data>type =xsd:string :see prose belowxml:base =<uri>xml:id = IDxml:lang =xsd:stringxml:space = ("default" |"preserve")Content: #PCDATA | (Metadata.class*,chunk+) | (Metadata.class*,source+)</data>

If simple data embedding is used, i.e., the content of thedata element is one or more text nodes, then anencoding attributemay be specified, and, if not specified, must be considered to bebase64.If chunked or sourced data embedding is used, i.e., the content of thedata element contains any childchunk orsource element, thenanencoding attribute must not be specified, and, if specified, must be ignoredfor the purpose of content processing.

If alength attribute is specified, then it must denote the number of decoded bytes in the byte sequence represented by thedata element. When decoding, if a specified length value does not match the number of decoded bytes, then a zero length byte sequence must be returned.If nolength attribute is specified, then the data resource is considered to have a length equal to the actual number of decoded bytes.Alength attribute must not be specified when using sourced data embedding.

If simple or chunked data embedding is used, atype attribute must be specified,and must correspond with the media (content) type of the data resource. In these cases, if there is no defined type, the typeapplication/octet-streamshould be used. In the case of sourced data embedding, the media (content) type of the resolvedsource elementis used as the type.

If atype attribute is not specified or resolved or is specified as a generic type,such asapplication/octet-stream, and additional format information is known about a referenced data resource that cannot beexpressed in a Media Type[MIME Media Types] parameter,then aformat attribute may be specified as a hint to the content processor.

The use of simple data embedding is illustrated by the following examples.

<head>  <resources>    <data xml:id="sharedImageData" type="image/png" length="119">      iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAIAAACQd1PeAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8      YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAAAMSURBVBhXY2BgYAAAAAQAAVzN/2kAAAAASUVORK5CYII=    </data>    <image xml:id="sharedImage">      <source src="#sharedImageData"/>    </image>  </resources></head>...<body xmlns:tts="http://www.w3.org/ns/ttml#styling">  <div tts:backgroundImage="#sharedImage"/>  <div tts:backgroundImage="#sharedImage"/></body>

<div>  <metadata xmlns:ttm="http://www.w3.org/ns/ttml#metadata">    <ttm:desc>caption with metadata containing tunneled data</ttm:desc>    <data encoding="base64">      TWFuIGlzIGRpc3Rpbmd1aXNoZWQsIG5vdCBvbmx5IGJ5IGhpcyByZWFzb24sIGJ1dCBieSB0aGlz      IHNpbmd1bGFyIHBhc3Npb24gZnJvbSBvdGhlciBhbmltYWxzLCB3aGljaCBpcyBhIGx1c3Qgb2Yg      dGhlIG1pbmQsIHRoYXQgYnkgYSBwZXJzZXZlcmFuY2Ugb2YgZGVsaWdodCBpbiB0aGUgY29udGlu      dWVkIGFuZCBpbmRlZmF0aWdhYmxlIGdlbmVyYXRpb24gb2Yga25vd2xlZGdlLCBleGNlZWRzIHRo      ZSBzaG9ydCB2ZWhlbWVuY2Ugb2YgYW55IGNhcm5hbCBwbGVhc3VyZS4=    </data>  </metadata>  <p>Caption with Tunneled Data</p></div>

<div>  <image>    <source>      <data type="image/png" length="119">        iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAIAAACQd1PeAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8        YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAAAMSURBVBhXY2BgYAAAAAQAAVzN/2kAAAAASUVORK5CYII=      </data>    </source>  </image></div>

9.1.4 font

Thefont element is used to define or refer to afont resource.

Afont element may appear as a child of aresources element, referred to as afont defining context.

Thefont element accepts as its childrenzero or more elements in theMetadata.class element group followed by zero or moresource elements.

<fontcondition =<condition>  family =xsd:string  range =<unicode-range>  style = ("normal" |"italic" |"oblique") :see prose belowsrc =<font>type =xsd:string  weight = ("normal" |"bold") :see prose belowxml:base =<uri>xml:id = IDxml:lang =xsd:stringxml:space = ("default" |"preserve")Content:Metadata.class*,source*</font>

Afont element defines afont resource by(1) referring to abuilt-in data resource,(2) referring to anexternal data resource, or(3) defining or referring to anembedded data resource,where thedata resource contains font content.

If afont element specifies asrc attribute, then it must not specify achildsource element. Conversely,if afont element does not specify asrc attribute, then it must specify one or morechildsource elements.

If afont element specifies asrc attribute and its value does not refer to a fragment of theenclosing document instance, then it should specify atype attribute, in which case the value of thetype attribute must correspond with the media (content) typeof the referenced resource. Otherwise, atype attribute must not be specified.

If any of thefamily,range,style, orweight attributes are specified, thenthey override the family name, supported character ranges, style, and weight of the actualfont resource. In particular,if the specified attribute value(s) differ from the value(s) of these font characteristics as encoded in thefont resource, thenthe specified attribute value(s) are to be used instead of the font characteristics encoded in thefont resource.

If any of thefamily,range,style, orweight attributes are not specified, then their valuesmust be considered to be equal to the value(s) of the same named font characteristics encoded in thefont resource.

For the purpose of dereferencing (downloading) font resources, acontent processormay defer the downloading process until such time that the content of the font resource is necessary in order to perform the necessary(transformation or presentation) processing.

The use of thefont element is illustrated by the following example.

...<head>  <resources>    <data xml:id="lastResortFont" type="application/font-woff">      ...base64 encoded data ...    </data>    <font family="MyFont" range="u+20-7f,u+90-9f">      <source src="http://example.com/fonts/myfont.otf" type="font/otf"/>      <source src="#lastResortFont"/>    </font>  </resources></head>...<p tts:fontFamily="MyFont">use my font or last resort font</p>...

9.1.5 image

Theimage element is used to define or refer to animage resource.

Animage element may appear in two contexts: (1) as a child of aresources element and(2) as a child of an element in theBlock.class element group, namely, as a child of adiv orp element, oras a child of aspan element. The former is referred to as animage defining context, the latter as animage presentation context.

When animage element appears in animage defining context, itserves as a sharable definition of animage resource that may be referenced by anotherimage element or byatts:backgroundImage style attributein theenclosing document instance.

When animage element appears in animage presentation context, itserves as a non-sharable definition of animage resource that implies presentation (rendering) semantics.

When animage element appears as a child of adiv element, then its presentationproduces a block area in which the image is rendered; i.e., a block boundary is implied before and after theimage element. In contrast,when animage element appears as a child of ap orspanelement, then its presentation produces an inline area in which the image is rendered; i.e., no block boundary is implied before and after theimage element.

The presentation of animage resource referenced by atts:backgroundImage style attribute must not affect content layout.

Theimage element accepts as its childrenzero or more elements in theMetadata.class element group, followed byzero or more elements in theAnimation.class element group, followed byzero or moresource elements.

<imageanimate = IDREFSbegin =<time-expression>condition =<condition>dur =<time-expression>end =<time-expression>region = IDREFsrc =<image>style = IDREFStimeContainer = ("par" |"seq")type =xsd:stringxlink:arcrole =<uri-list>xlink:href =<uri>xlink:role =<uri-list>xlink:show = ("new" |"replace" |"embed" |"other" |"none") : newxlink:title =xsd:stringxml:base =<uri>xml:id = IDxml:lang =xsd:stringxml:space = ("default" |"preserve")  {any attributes inTT Style Namespaces}  {any attributes in TT Metadata Namespace}Content:Metadata.class*,Animation.class*,source*</image>

Animage element defines animage resource by(1) referring to abuilt-in data resource,(2) referring to anexternal data resource, or(3) defining or referring to anembedded data resource,where thedata resource contains image content.

If animage element specifies asrc attribute, then it must not specify achildsource element. Conversely,if animage element does not specify asrc attribute, then it must specify one or morechildsource elements.

If animage element specifies asrc attribute and its value does not refer to a fragment of theenclosing document instance, then it should specify atype attribute, in which case the value of thetype attribute must correspond with the media (content) typeof the referenced resource. Otherwise, atype attribute must not be specified.

Animage element may specify antts:extentstyle attribute in order to specify the presentation width or height of the imagewhen intrinsic width or height information is not available or is intended to be overridden. If this attribute is specified on both animage element in animage presentation context and on theimage element in animage defining context to which the former refers, thenthe attribute specified on the former takes precedence over the one specified on the latter. Presentation of an image to which atts:extent style attribute applies is subject to a (possibly anamorphic)scaling operation in order to obtain the width and height of the specified extent.

The linking attributesxlink:* may be used to link animage element with related content, using thespecified location (href), roles, and title. The behavior of link activation is affected by thexlink:show attribute,the precise meaning of which is determined by thedocument processing context.

When animage appears in animage defining context the following additionalconstraints apply:

1. attributesanimate,begin,dur,end,region, andtimeContainer must not be specified, and, if they appear, must be ignored for the purpose of presentation processing;

2. elements from theAnimation.class element group must not appear as child elements, and, if they appear, must be ignored for the purpose of presentation processing.

The use of theimage element is illustrated by the following examples.

<div>  <p>This division has a content image that appears as a block area after this paragraph.</p>  <image src="http://example.com/images/caption.png" type="image/png"/><div>...<div tts:backgroundImage="http://example.com/images/background.png">  <p>This division has a background image that appears under this paragraph.</p><div>...

<head>  <resources>    <data xml:id="caption" type="image/png" length="119">      iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAIAAACQd1PeAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8      YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAAAMSURBVBhXY2BgYAAAAAQAAVzN/2kAAAAASUVORK5CYII=    </data>  </resources></head><body>  <div>    <p>      <image>        <source src="#caption"/>      </image>    <p>    ...    <p>      <image>        <source src="#caption"/>      </image>    <p>  </div></body>

<div>  <image>    <source src="http://example.com/images/caption.png" type="image/png"/>    <source>      <data type="image/png" length="119">        iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAIAAACQd1PeAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8        YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAAAMSURBVBhXY2BgYAAAAAQAAVzN/2kAAAAASUVORK5CYII=      </data>    </source>  </image></div>

9.1.6 resources

Theresources element is a container element used to groupdefinitions of embedded content, including metadata that applies to this embedded content.

Theresources element accepts as its children zero or moreelements in theMetadata.class element group,followed by zero or more elements in theData.class,Embedded.class, orFont.class element groups.

<resourcesxml:base =<uri>xml:id = IDxml:lang =xsd:stringxml:space = ("default" |"preserve")Content:Metadata.class*, (Data.class|Embedded.class|Font.class)*</resources>

To the extent that time semantics apply to the content of theresources element, the implied time interval of this element isdefined to be coterminous with theroot temporal extent.

9.1.7 source

Thesource element is used to specify the source of anembedded content resource.

Thesource element accepts as its childrenzero or more elements in theMetadata.class element group followed by zero or onedata element.

If asource element specifies asrc attribute, then it must not specify achilddata element, in which case it is referred to asanexternal source if thesrc attribute refers to an external resource, oranon-nested embedded sourceif thesrc attribute refers to an embedded resourcein theenclosing document instance.

If asource element does not specify asrc attribute, then it must specify achilddata element, in which case it is referred to asanested embedded source.

Asource element must not have an ancestorsource element.

<sourcecondition =<condition>format =<data-format>src =<data>type =xsd:stringxml:base =<uri>xml:id = IDxml:lang =xsd:stringxml:space = ("default" |"preserve")Content:Metadata.class*,data?</source>

If aformat attribute is specified, then it provides additional hint information about the format (i.e., formal syntax) of theembedded content. Such information may be useful in cases where no standard media (content) type label has been defined or the information cannot beexpressed in a Media Type parameter[MIME Media Types]. Depending on thecontext of use of asource element, the values of this attribute may be further constrained.

If asrc attribute is specified and its value refers to a fragment of theenclosing document instance,then there must be adata element child of aresourceselement which is identified by that fragment, i.e., has anxml:id attribute, the value of which matches the fragment identifier.

If asrc attribute is specified and its value does not refer to a fragment of theenclosing document instance, thenatype attribute should be specified, in which case it must correspond with the media (content) typeof the referenced resource.

If asrc attribute is specified and its value does refer to a fragment of theenclosing document instance, thenatype attribute must not be specified; rather, the content type of the embedded resource is determined bythe value of thetype attribute on the referenced or embeddeddata element.

The use of thesource element is illustrated by the following examples.

...<image>  <source src="http://example.com/images/caption.png" type="image/png"/></image>...

...<data xml:id="caption" type="image/png" length="119">  iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAIAAACQd1PeAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8  YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAAAMSURBVBhXY2BgYAAAAAQAAVzN/2kAAAAASUVORK5CYII=</data>...<image>  <source src="#caption"/></image>...

...<image>  <source>    <data type="image/png" length="119">      iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAIAAACQd1PeAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8      YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAAAMSURBVBhXY2BgYAAAAAQAAVzN/2kAAAAASUVORK5CYII=    </data>  </source></image>...

9.2.1 encoding

Theencoding attribute is used to specify the encoding format of data.

Theencoding attribute may be specified by an instance of the followingelement types:

• chunk

• data

If specified, the value of anencoding attribute must take one of the following values as defined by[Data Encodings]:

• base16

• base32

• base32hex

• base64

• base64url

If not specified, thenbase64 semantics apply.

9.2.2 format

Theformat attribute is used to specify hints about the media (content) format ofan embedded content resource beyond media (content) type informationprovided by atype attribute.

Theformat attribute may be specified by an instance of the followingelement types:

• data

• source

The value of aformat attribute must adhere to a<data-format> expression.

Depending on the context of use, additional constraints may apply.

9.2.3 src

Thesrc attribute is used to specify the location or an identifier that maps to the location of data resource.

Thesrc attribute may be specified by an instance of the followingelement types:

• audio

• data

• font

• image

• source

If specified, the value of asrc attribute must adhere to the value syntax of the<uri> value syntax.

Depending on the context of use, additional constraints may apply.

9.2.4 type

Thetype attribute is used to specify the media (content) type of data resource, and may express additionalparameters that characterize the data.

Thetype attribute may be specified by an instance of the followingelement types:

• audio

• data

• font

• image

If specified, the value of atype attribute must adhere to the value syntax of theContent-TypeMIME header defined by[MIME], §5.1.

If not specified, then the media (content) type is unknown or deliberately unspecified.

When decoding a data resource for which atype attribute is specified, then content processingmust respect the specified type whether it is correct or not. That is, if atype attribute mis-specifies thetype of a data resource, then content processing must not attempt to override that type by performing contentsniffing.