2. The SMIL 3.0 Modules

This section is informative.

Since the publication of SMIL 1.0 [SMIL10], interest in the integration of SMIL concepts with the HTML, the HyperText Markup Language [HTML4], and other XML languages, has grown. Likewise, the W3C HTML Working Group has specified XHTML, the Extensible HyperText Markup Language [XHTML10], in preparation to subset, extend, and integrate it with other languages. The strategy considered for integrating respective functionality with other XML-based languages is based on the concepts of modularization and profiling [SMIL-MOD], [XMOD].

Modularization is an approach in which markup functionality is specified as a set of modules that contain semantically-related XML elements, attributes, and attribute values. Profiling is the creation of an XML-based language through combining these modules, in order to provide the functionality required by a particular application.

Profiling introduces the ability to tailor an XML-based language to specific needs, e.g. to optimize presentation and interaction for the client's capabilities. Profiling also adds the ability for integrating functionality from other markup languages, releasing the language designer from specifying that functionality. Moreover, it provides for consistency in markup through the use of the same model to incorporate a function. Identical constructs ease authoring, while at the user agent side there is a potential for re-use of code. For example, a scheduler supporting SMIL timing and synchronization functionality could be used for SMIL documents, XHTML+SMIL documents, and SVG documents.

Modularization enables language designers to specify dedicated markup intended for integration with other, existing, profiles. Examples of specifications intended for such integration are MathML and XForms [MathML], [XFORMS10].

Modularization and profiling use the extensibility properties of XML, and related technology like XML namespaces and XML Schema [XML11], [XML-NS], [XSCHEMA].

This part of the SMIL 3.0 specification describes the framework on which SMIL modularization and profiling is based, and specifies the SMIL 3.0 Modules, their identifiers, and the requirements for conformance within this framework.

This section is informative.

The modularization approach used in this specification derives from that set forth in XHTML Modularization [XMOD]. The framework on which SMIL modularization and profiling is based, is informally described here.

A Module is a collection of semantically-related XML elements, attributes, and attribute values that represents a unit of functionality. Modules are defined in coherent sets.

A Profile is a combination of modules. Modules are atomic, i.e. they may not be subset when included in a profile. Furthermore, a module specification may include a set of integration requirements, to which profiles that include the module must comply.

Commonly, there is a main profile that incorporates nearly all the modules associated with a single namespace. For this version of SMIL, this is the SMIL 3.0 Language profile.

Other profiles may be specified that are subsets of the larger one, or that incorporate a mixture of modules associated with different namespaces. SMIL 3.0 Tiny is an example of the first, XHTML+SMIL of the latter.

Several of SMIL's modules define features that that characterize the core of the functionality provided by SMIL. This is expressed by the notions of host language and integration set. Both of them relate to a set of conformance requirements for language profiles, which includes the requirement to incorporate at least the core set of modules. The set may be different for a host language and an integration set. A host language must incorporate the Structure module; an integration set need not. There may be other differences as well.

The main purpose of profile conformance is to enhance interoperability. Preferably, the mandatory modules for host language conformance are defined in such a way that any document interchanged in a conforming profile will yield a reasonable presentation when the document renderer, while supporting the associated mandatory module set, would ignore all other (unknown) elements and attributes. Here, "reasonable presentation" is to be understood as something intelligible, which is not necessarily a close reflection of the author's original intentions. To achieve the latter, a negotiation would have to be conducted to agree on the specific profile to be used for the document interchange.

This section is informative.

SMIL 3.0 specification provides three classes of changes to the SMIL 2.1 Recommendation, among the functional areas;

1. New Modules are introduced (e.g. the MediaPanZoom module, MediaOpacity, BasicText, TextStyling, TextMotion; StateTest, UserState, StateSubmission, StateInterpolation; StructureLayout modules and DOMTimingMethods.
2. Former SMIL Modules are revised allowing extended functionalities (example are Metainformation, BasicLayout, MediaParam modules).
3. Former SMIL Modules are unchanged; the modules, elements and attributes semantics remain the same as in SMIL2.1 [SMIL21]. There are no major changes to the modules; apart from minor issues related to typos, links and references.

The following functional areas are affected by SMIL 3.0:

DOM

• The new chapter SMIL 3.0 DOM describes how the DOM may be used in SMIL 3.0.

Content Control

This functional area is currently unchanged, apart from repartitioning of the content control module structure in order to support the SMIL Tiny profile. In a future version the content control mechanisms specified will be modified to better align with the expression and test logic being developed within the SMIL 3.0 State modules.

• The RequiredContentControl, defining the systemRequired attribute to specify the URI of modules required to process a particular SMIL file.

Layout

SMIL 3.0 extends the Layout capabilities as follows:

• The BasicLayout module is extended with the backgroundOpacity attribute, which specifies the background opacity of a region;
• A new StructureLayout module defines the layout element, to identify the layout mechanism used by a SMIL profile independently of the SMIL basic layout architecture.

Linking

SMIL 3.0 linking integrates the general features of the XHTML-2 access and role attributes as an extension and replacement for the accessKey attribute.

Media Object

• Introduction of the new MediaPanZoom module for panning and zooming over media content;
• Introduction of the new MediaOpacity module containing new rendering attributes for chroma key and opacity control;
• The former MediaParam module is extended with new attributes and split into MediaParam module and MediaRenderAttributes module.

SmilText

This new smilText functionality provides a new media type for use in SMIL presentations. The smilText modules provide a text container element with an explicit content model for defining in-line text, and a set of additional elements and attributes to control explicit in-line text rendering.

The following 3 modules are introduced in the new Text functional area allowing use of in-line text content:

• Introduction of the new BasicText module provides basic support for in-line text within a SMIL presentation;
• The new TextStyling adds styling capabilities of text;
• The new TextMotion module defines how text is added.

In addition, SMIL 3.0 also defines the smilText profile, which allows timed text markup to be placed in a light-weight external container.

Metainformation

Metainformation mechanisms in SMIL 3.0 provide a general purpose approach to attaching metainformation to any element within the presentation.

• The Metainformation module is extended as follows :
  - allowing meta-information to be placed on elements within the body instead of only in the head element.
  - the label attribute is added so that extended content information may be provided for document components.
  - the text in this section makes it clear that several different types of metainformation encodings may be used within a single presentation.

Structure

The new Identity module identifies the SMIL version and the SMIL profile. This replaces the former SMIL approach of defining separate namespaces for individual modules and profiles.

Timing

The SMIL 3.0 specification leaves the basic syntax and semantics of the SMIL 2.1 timing model [SMIL21-timing] unchanged apart from the following changes:

• The new module, DOMTimingMethods adds DOM methods;

State

The new modules in this section provide a mechanism whereby the document author may create more complex controlflow than what SMIL provides through the timing and content control modules, without having to go all the way of using a scripting language. One way to provide this is to allow a document to have some explicit state (think: variables) along with ways to modify, use and save this state.

The following 4 modules are introduced in the State functional areas:

• Introduction of the new StateTest module, containing extended content selection;
• The new UserState module, containing author-defined state;
• The new StateSubmission module, saving author-defined state;
• The new StateInterpolation module, allowing runtime modification to attribute values.

This section is informative.

This section describes how profiles could be defined using the SMIL 3.0 modular DTDs. The reader is assumed to be familiar with the mechanisms defined in "Modularization of XHTML" [XMOD], in particular Appendix D [XMOD-APPD] and Appendix E [XMOD-APPE]. In general, the SMIL 3.0 modular DTDs use the same mechanisms as the XHTML modular DTDs use. Exceptions to this are:

1. SMIL supports qualified attribute names for SMIL attributes that may appear on non-SMIL elements. This enables these attributes to use prefixes to indicate that they belong to the SMIL 3.0 namespace.
2. SMIL supports module level INCLUDE/IGNORE instead of XHTML's element/attlist level. Similar to XHTML Modularization, this prohibits profiles from importing only part of a module -- they have to support either all the elements and attributes or none.

Below, we give a short description of the files that are used to define the SMIL 3.0 modular DTDs. See the table and the end of the section for a complete list of the filenames involved.

Following the same mechanisms as the XHTML modular DTDs, the SMIL 3.0 specification places the XML element declarations (e.g. <!ELEMENT...>) and attribute list declarations (e.g. <!ATTLIST...>) of all SMIL 3.0 elements in separate files, the SMIL module files. A SMIL module file is provided for each functional area in the SMIL 3.0 specification (that is, there is a SMIL module file for animation, layout, timing, etc).

The SMIL module files are used in the normative definitions of the specification of the SMIL 3.0 Language profile. Usage of the same module files for defining other SMIL profiles is recommended, but not required. The requirements that SMIL profiles must follow are stated in the SMIL 3.0 specification, not in the DTD code.

To make the SMIL module files independent of each other, and independent of the profiles, the element and attribute declarations make heavy use of XML entities. This provides profiles with the necessary hooks to define the actual content models and attributes of the SMIL elements.

The SMIL 3.0 Language profile provides examples of how the SMIL module files may be used. Most of the DTD files are reused across the different profiles. Reused are the SMIL module files, the files that define the data types and the common attributes, the "qname" file that takes care of adding namespace prefixes if necessary, and the framework file, which takes care of including files in the appropriate order.

The file that is different for each profile is the driver file, and possibly the document model file. To define a new profile, one has to write the extension module(s), the driver file that defines which modules are used, and a document model file that defines the extended document model. A new profile that merely reuses SMIL 3.0 modules may not need a new document model file. The driver file and document model file are described in more detail below.

The driver file.

This is the file that would be referenced by a document's DOCTYPE declaration. Its main job is to define the modules and features that are included in the DTD. The file contains the following parts.

• If the SMIL element names are to be prefixed, this can be done by adding something like the following to the start of the profile:

  <!ENTITY % SMIL.prefixed "INCLUDE" >
<!ENTITY % SMIL.prefix "foobar" >

  Elements defined in their modules as, for example, <video> will become parsed as <foobar:video>. This also applies for SMIL attributes that appear on other elements, so, for example, "begin" becomes "foobar:begin". The default is that the qname prefix is empty -- that is, it is effectively turned off by default.

• The default value of the baseProfile should be defined. If not defined, the value defaults to #IMPLIED. For example:

  <!ENTITY % SMIL.baseProfile.default "#FIXED 'Language'">

• The modules to be included in the DTD need to be specified using entity definitions such as this, one for each included module:

  <!ENTITY % SMIL.Structure.module "INCLUDE" >

  The entity names are all of the form SMIL.ModuleName.module. The default for all modules is that they are not included.

• For each of the optional features and variants that are to be included, an entity needs to be defined as "INCLUDE". Here is a list of all possible entities:

  SMIL.animation-targetElement

  The targetElement attribute to specify the animation target is included. See The target element.

  SMIL.animation-XLinkTarget

  The XLink attributes to specify the animation target are included. See The target element.

  SMIL.transition-targetElement

  The targetElement attribute to specify the transitionFilter target is included.

  SMIL.transition-XLinkTarget

  The XLink attributes href, type, actuate, and show, to specify the transitionFilter target are included.

  SMIL.ITS-Attributes.module

  The Internationalization Tag Set (ITS) [ITS] attributes are included.

  SMIL.RoleAttributes.module

  The XHTML Role attributes are included. See XHTML Role Attribute Module.

  SMIL.submission-post

  The method attribute in the SMIL 3.0 State module is extended with the "post" value.

  SMIL.ContentControl.deprecated.module

  The deprecated hyphenated content control attributes are included.

  SMIL.MediaClipping.deprecated.module

  The deprecated hyphenated MediaClipping attributes are included.

  SMIL.RepeatTiming.deprecated.module

  The deprecated repeat attribute is included.

  SMIL.BasicLinking.deprecated.module

  The deprecated anchor element is included.

  SMIL.TextExternal.module

  Extra attributes needed by the smilText profile are included.

  The default for these optional features is that they are not included.

• The document model file that is to be used needs to be defined:

  <!ENTITY % smil-model.mod PUBLIC "-//W3C//ENTITIES SMIL 3.0 Document Model 1.0//EN" "smil-profile-model-1.mod" >

  All standard SMIL DTDs use the same document model file.

• The framework file needs to be included. The framework file will subsequently include the data type, common attributes, qname and document model file.

• The SMIL module files that are used by this profile need to be included.

The document model file.

The document model file contains the XML entities that are used by the SMIL module files to define the content models and attribute lists of the elements in that profile.

Content models generally differ from profile to profile, or contain elements from other modules. To avoid these dependencies in the SMIL module files, content models may be defined in the document model file. The (dummy) default content model as defined in the SMIL module files is "EMPTY" for all SMIL 3.0 elements.

For the same reasons, the SMIL module files only define a default attribute list for their elements. This default list only contains the SMIL 3.0 core attributes and the attributes that are defined in the same SMIL module file. All other attributes may be added to this default list by defining the appropriate XML entities. For example, the Media Objects Module file only adds the core and media related attributes on the media objects; other attributes, such as the timing attributes, are added to this list by the document model file.

Table 7: Formal public identifiers and system identifiers of all files used in the SMIL 3.0 modular DTDs.

Driver files for the predefined profiles
-//W3C//DTD SMIL 3.0 Language//EN	http://www.w3.org/2008/SMIL30/SMIL30Language.dtd
-//W3C//DTD SMIL 3.0 Unified Mobile//EN	http://www.w3.org/2008/SMIL30/SMIL30UnifiedMobile.dtd
-//W3C//DTD SMIL 3.0 Daisy//EN	http://www.w3.org/2008/SMIL30/SMIL30Daisy.dtd
-//W3C//DTD SMIL 3.0 Tiny//EN	http://www.w3.org/2008/SMIL30/SMIL30Tiny.dtd
-//W3C//DTD SMIL 3.0 smilText//EN	http://www.w3.org/2008/SMIL30/SMIL30smilText.dtd

Document model files for the predefined profiles
-//W3C//ENTITIES SMIL 3.0 Document Model 1.0//EN	http://www.w3.org/2008/SMIL30/smil-profile-model-1.mod

SMIL 3.0 module files
-//W3C//ELEMENTS SMIL 3.0 Animation//EN	http://www.w3.org/2008/SMIL30/SMIL-anim.mod
-//W3C//ELEMENTS SMIL 3.0 Content Control//EN	http://www.w3.org/2008/SMIL30/SMIL-control.mod
-//W3C//ELEMENTS SMIL 3.0 Layout//EN	http://www.w3.org/2008/SMIL30/SMIL-layout.mod
-//W3C//ELEMENTS SMIL 3.0 Linking//EN	http://www.w3.org/2008/SMIL30/SMIL-link.mod
-//W3C//ELEMENTS SMIL 3.0 Media Objects//EN	http://www.w3.org/2008/SMIL30/SMIL-media.mod
-//W3C//ELEMENTS SMIL 3.0 Document Metainformation//EN	http://www.w3.org/2008/SMIL30/SMIL-metainformation.mod
-//W3C//ELEMENTS SMIL 3.0 SMILtext//EN	http://www.w3.org/2008/SMIL30/SMIL-smiltext.mod
-//W3C//ELEMENTS SMIL 3.0 State//EN	http://www.w3.org/2008/SMIL30/SMIL-state.mod
-//W3C//ELEMENTS SMIL 3.0 Document Structure//EN	http://www.w3.org/2008/SMIL30/SMIL-struct.mod
-//W3C//ELEMENTS SMIL 3.0 Timesheet//EN	http://www.w3.org/2008/SMIL30/SMIL-timesheet.mod
-//W3C//ELEMENTS SMIL 3.0 Timing//EN	http://www.w3.org/2008/SMIL30/SMIL-timing.mod
-//W3C//ELEMENTS SMIL 3.0 Transition//EN	http://www.w3.org/2008/SMIL30/SMIL-transition.mod

Other utilities: data types, common attributes, qname and frame work files
-//W3C//ENTITIES SMIL 3.0 Common Attributes 1.0//EN	http://www.w3.org/2008/SMIL30/smil-attribs-1.mod
-//W3C//ENTITIES SMIL 3.0 Datatypes 1.0//EN	http://www.w3.org/2008/SMIL30/smil-datatypes-1.mod
-//W3C//ENTITIES SMIL 3.0 Modular Framework 1.0//EN	http://www.w3.org/2008/SMIL30/smil-framework-1.mod
-//W3C//ENTITIES SMIL 3.0 Qualified Names 1.0//EN	http://www.w3.org/2008/SMIL30/smil-qname-1.mod