Compound Document by Reference Framework 1.0

1.1 Scope

(This section is informative)

Combining content delivery formats can often be desirable in order to provide a seamless experience for the user.

For example, XHTML-formatted content can be augmented by SVG objects, to create a more dynamic, interactive and self adjusting presentation. A set of standard rules is required in order to provide this capability across a range of user agents and devices.

These are examples of possible Compound Document profiles:

• XHTML + SVG + MathML
• XHTML + SMIL
• XHTML + XForms
• XHTML + VoiceML

This document defines a generic Compound Document by Reference Framework (CDRF) that defines a language-independent processing model for combining arbitrary document formats.

NOTE: The Compound Document Framework is language-independent. While it is clearly meant to serve as the basis for integrating W3C's family of XML formats within its Interaction Domain (e.g., CSS, MathML, SMIL, SVG, VoiceXML, XForms, XHTML, XSL) with each other, it can also be used to integrate non-W3C formats with W3C formats or integrate non-W3C formats with other non-W3C formats.

1.2 Related Documents

(This section is informative)

WICD Core

WICD Core [WICDCORE] is the foundation of rich multimedia content and describes rules for combining Hypertext Markup Language (XHTML) and scalable child objects, such as Scalable Vector Graphics (SVG) in a non device specific manner. WICD stands for Web Integrated Compound Document.

WICD Core builds upon CDRF.

1.3 Reference and Inclusion

(This section is informative)

A namespace uniquely identifies a set of names so that there is no ambiguity when objects having different origins but the same names are mixed together. An XML namespace is a collection of element type and attribute names. These element types and attribute names are uniquely identified by the name of the unique XML namespace of which they are a part. In an XML document, any element type or attribute name can thus have a two-part name consisting of the namespace name and the element or attribute name.

A Compound Document by inclusion combines XML markup from several namespaces into a single physical document. A number of standards exist, and continue to be developed, that are descriptions of XML markup within a single namespace. XHTML, XForms, VoiceXML, and MathML are some of the prominent examples of such standards, each having its own namespace. Each of these specifications focuses on one aspect of rich-content development. For example, XForms focuses on data collection and submission, VoiceXML on speech, and MathML on the display of mathematical notations.

To authors of content, each of these many standards is useful and important. However, it is the combination of elements of any number of these standards that lends true flexibility and power to rich document creation. A document may exist to be displayed within a web browser, to display an input form, with a scalable graphic and a bit of mathematical notation, all on the same page. XHTML, XForms, SVG, and MathML, respectively, serve these needs, and could therefore be combined into a single multi-namespace document.

Consider this simple example, a Compound Document combining XHTML and MathML. The namespace declarations are marked by an appended comment to match the numbered namespaces listed below in the XML source in Example 1.

1. XHTML Namespace declaration. The namespace for XHTML 1.0 is declared. Each XHTML element in the example below is qualified with the xhtml: namespace prefix.

2. MathML Namespace declaration. The namespace for MathML 2.0 is declared. Each MathML element in the example below is qualified with the mathml: prefix.

A Compound Document example:

<?xml version="1.0" encoding="iso-8859-1"?>
<xhtml:html xmlns:xhtml="http://www.w3.org/1999/xhtml">   <!-- 1 -->
  <xhtml:body>
    <xhtml:h1>A Compound Document</xhtml:h1>
    <xhtml:p>A simple formula using MathML in XHTML.</xhtml:p>
    <mathml:math xmlns:mathml="http://www.w3.org/1998/Math/MathML">   <!-- 2 -->
      <mathml:mrow>
        <mathml:msqrt>
          <mathml:mn>49</mathml:mn>
        </mathml:msqrt>
        <mathml:mo>=</mathml:mo>
        <mathml:mn>7</mathml:mn>
      </mathml:mrow>
    </mathml:math>
  </xhtml:body>
</xhtml:html>
          

Example 1: A Simple Compound Document

Figure 1 (above): Rendered Simple Compound Document - This is a rendered version of the simple Compound Document in Example 1 which combines XHTML and MathML for rich content.

Compound Documents may be composed of a single document that contains multiple namespaces, as seen in Example 1. This is a Compound Document “by Inclusion” (CDI). However, a Compound Document may also be composed over several documents in which one document of a particular namespace references another separate document of a different namespace.

For example, a root or top-most document might contain XHTML content for defining and formatting a page. This parent XHTML document can reference another document, of another namespace, through the use of the XHTML <object> tag. This can be repeated for as many documents as necessary. The root document plus this collection of separate, referenced documents is considered a Compound Document “by Reference” (CDR). See Figure 2 for a simple CDR document in which an XHTML root document contains a reference to a separate SVG child document having markup for three colored circles.

Figure 2 (above): Compound Document by Reference - A simple Compound Document by reference where a XHTML document references a separate SVG document. Below you see the two markup fragments.

XHTML:

<?xml version="1.0"?>
<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <title>circles</title>
  </head>
  <body>
    <object height="350" width="600" type="image/svg+xml" data="circles.svg"/>
  </body>
</html>

SVG:

<?xml version="1.0" encoding="UTF-8"?>
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" baseProfile="tiny" version="1.2">
  <g fill-opacity="0.7" stroke="black" stroke-width="0.2cm">
    <circle fill="red" cx="6cm" cy="2cm" transform="translate(0,50)" r="100"/>
    <circle fill="blue" cx="6cm" cy="2cm" transform="translate(70,150)" r="100"/>
    <circle fill="green" cx="6cm" cy="2cm" transform="translate(-70,150)" r="100"/>
  </g>
</svg>

And of course, a Compound Document may be a hybrid of both compound document by inclusion and Compound Document by reference.

1.4 Referencing Child Objects

(This section is informative)

Each hosting language has its own methods for referencing child objects. These provide different functionality, but the following section describes (some of) the common functionality.

<object type="..." data="...">
  <param name="param1" value="true" />
  <param name="param2" value="123" />
</object>

<svg xmlns="http://www.w3.org/2000/svg">
    <foreignObject>
        <metadata>
           param=value;
           param=value
        </metadata>
    </foreignObject>
</svg>

<ref src="http://www.example.com/herbert.face">
  <param name="mood" value="surly" valuetype="data"/>
  <param name="accessories" value="baseball-cap,nose-ring" valuetype="data"/>
</ref>

1.5 Identification and Versioning

(This section is informative)

A distinct identification of the supported Compound Document capabilities is often not possible by advertising a list of supported content types. Such a list is not sufficient to describe the supported capabilities between compound languages. A unique profile identifier is often better suited to describe such characteristics. CDRF profiles may define their identification and versioning criteria, which should utilize the mechanisms readily available from the root language. For example, if the root language is XHTML, then the content type of "application/xhtml+xml" can be used. It can then be used with the optional parameter of "profile", with a value of a URI that both identifies the profile and its version.

2.1 Document Object Model

Compound document profiles which leverage the Compound Document Framework and which support scripting must have scripting interfaces that are compatible with the uDOM, or implement a superset such as the DOM Level 3 Core Specification [DOM3CORE].

Compound Document profiles may subset DOM Level 3 Core [DOM3CORE], but any DOM Core subsetting should be coordinated with other related DOM subsetting standards efforts. For example, mobile subset efforts for W3C languages such as XHTML, SVG, SMIL and XForms should be coordinated with each other because of the high probability that Compound Document profiles will be defined that combine these languages.

A Compound Document using references consists of a root document which may have one or more child documents, which may in turn have its own child documents. Each child document contains elements and attributes from one or more namespaces. The consequence of this is that each child document generates its own DOM. The interaction points between parent and child documents of a Compound Document are at referencing DOM nodes in a parent document. The Compound Document framework provides a means of accessing the DOMs of the child and parent documents.

Each child document DOM generates its own scripting execution context. Each child DOM scripting execution context provides access to its corresponding global object. The CSS [CSS21] style-sheet cascade is applied to each DOM in isolation. CSS property inheritance is inhibited at document boundaries. It is possible for a content author to use child-to-parent (see 2.1.2 Child to Parent DOM Access) or parent-to-child (see 2.1.3 Parent to Child DOM Access) to propagate specific styling properties.

<?xml version="1.0" encoding="UTF-8"?>
<svg xmlns="http://www.w3.org/2000/svg"
  height="20" version="1.1" width="20">
	<title>child-svg</title>
	<rect fill="blue" height="20"
		onload="alert('Child has seen: ' + 
          document.defaultView.frameElement.ownerDocument.title)"
		width="20" x="10" y="10" />
</svg>

<?xml version="1.0" encoding="UTF-8"?>
<html xmlns="http://www.w3.org/1999/xhtml"> 
  <head> 
    <title>parent-xhtml</title>
  </head> 
  <body> 
    <object data="child.svg" 
      onload="alert('Parent has seen: ' + 
        this.contentDocument.getElementsByTagNameNS(
          'http://www.w3.org/2000/svg',
          'title') [0].textContent)"  />
  </body>
</html>

2.2 Events

Compound Document profiles which leverage the Compound Document Framework and which support events and interactivity must have event interfaces and an event processing model that are compatible with the DOM Level 3 Events Specification [DOM3EVENTS].

Compound Document profiles may subset DOM Level 3 Events [DOM3EVENTS], but any DOM Events subsetting should be coordinated with other related DOM subsetting standards efforts. For example, mobile subset efforts for W3C languages such as XHTML, SVG, SMIL and XForms should be coordinated with each other because of the high probability that Compound Document profiles will be defined that combine these languages.

var x = document.createEvent("CustomEvent");
x.initCustomEventNS("http://example.org/test", "test", true, false, null);
window.frameElement.dispatchEvent(x);