This element holds text (mixed content) in places where alternatives can be presented, providing a textual alternative. For example, inside the <alternatives> wrapper element, a <textual-form> can provide an alternative version of an equation, graphic, or table. This alternative textual version may be a direct textual representation of an object (such as a Unicode value for a special character or the full text of an equation in ASCII characters), or a simplified textual version of the object (for display by devices not able to cope with the object), or a text-dump of the contents of a binary object (for example, the full text-dump of the cells of a table to accompany a graphic version of the table).
Usage Display Alternative: One use of the <textual-form> element is inside a display object (such as an equation or figure) to provide an equivalent display alternative for a graphic object. For example, a display equation (<disp-formula>), may be provided in several equivalent, interchangeable forms within an <alternatives> element:
- as a MathML-encoded equation (<mml:math>),
- as a plain text alternative which uses ASCII characters and superscripts (<textual-form>), and
- as a <graphic> such as a tif or jpg.
Similarly, a graphic can be provided with a simpler (as opposed to equivalent) alternative form, to provide gentle degradation for hardware that cannot process the graphic or media object.
Usage Special Characters: The <textual-form> element can also be used to supply a textual or Unicode description of a special character that is being defined using a <private-char> element, as an alternative to bitmaps or graphics. For example, an <alternatives> element could be used to describe multiple ways of defining the character:
- one as a graphic (<inline-graphic>),
- one as a bitmap (<glyph-data> bitmap inside <private-char> element), and
- one or more as textual alternatives (<textual-form>) to name alternative characters in the Unicode Standard that can be used to create a visual approximation of the character being defined.
Usage Search Text: The <textual-form> element can also be used to supply the text of an object for searching. In such a usage, it is not intended that the <textual-form> be displayed to the user, only that it provide a textual view of the object to a search system. This technique can allow unsearchable binary formats, such as graphics and untagged tables represented as graphics, to be represented in a form that can be searched or indexed.
<!ELEMENT textual-form (#PCDATA %textual-form-elements;)* >
Expanded Content Model
(#PCDATA | bold | fixed-case | italic | monospace | overline | roman | sans-serif | sc | strike | underline | ruby | inline-graphic | private-char | tex-math | mml:math | named-content | styled-content | sub | sup)*
Any combination of:
- Text, numbers, or special characters
- Emphasis Elements
- Inline Display Elements
- Math Elements
- <named-content> Named Special (Subject) Content
- <styled-content> Styled Special (Subject) Content
- Baseline Change Elements
This element may be contained in:
A formula/equation as a graphic, a MathML-tagged equation, and a textual form:
... <disp-formula> <alternatives> <textual-form>(a + 3)<sup>2</sup> - (10 - b) = 24</textual-form> <graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fors2682.f3" > <object-id>463492</object-id> </graphic> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mfenced> <mml:mrow> <mml:mi>a</mml:mi> <mml:mo>+</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:mfenced> <mml:mn>2</mml:mn> </mml:msup> <mml:mo>−</mml:mo> <mml:mfenced> <mml:mrow> <mml:mi>10</mml:mi> <mml:mo>−</mml:mo> <mml:mn>b</mml:mn> </mml:mrow> </mml:mfenced> <mml:mo>=</mml:mo> <mml:mn>24</mml:mn> </mml:mrow> </mml:math> </alternatives> </disp-formula> ...
An example of a triple bond glyph. To a chemist, a triple bond is not the same as Unicode x2261, but using alternatives, as shown below, is sometimes the easiest way to display the character visually and still stay within Unicode:
... <alternatives> <textual-form specific-use="unicode-look-alike">≡</textual-form> <private-char name="Triple Bond" description="Chemistry Triple Bond"> <glyph-data id="tbond" format="PBM" resolution="300" x-size="16" y-size="32"> 0000000000000000000000000000000 0000000000000000000000000000000 0000000000000000000000000000000 0000000000000000000000000000000 0000000000000000000000000000000 0001111111111111111111111100000 0000000000000000000000000000000 0000000000000000000000000000000 0001111111111111111111111100000 0000000000000000000000000000000 0000000000000000000000000000000 0001111111111111111111111100000 0000000000000000000000000000000 0000000000000000000000000000000 0000000000000000000000000000000 0000000000000000000000000000000 0000000000000000000000000000000 0000000000000000000000000000000 </glyph-data> </private-char> </alternatives> ...
A text-dump of a table, for use in searching and indexing:
... <table-wrap id="tbl-3"> <label>3</label> <caption> <title>Categories of Color Immediacy</title> </caption> <alternatives> <graphic id="tbl3-jpg" xlink:href="immediacy-tab3.jpg" /> <textual-form specific-use="search/index"> Description of Color Category Number of Immediacy Events 1. Drew parallels between green and blue relationships 21 events 2. Encouraged expression of yellow feelings 12 events 3. Admitted red termination 8 events ... Note. These results are based on 44 immediacy events. Categories were not mutually exclusive, and several types of immediacy may occur in each event. Each category was recorded only once per event. </textual-form> </alternatives> </table-wrap> ...
An alternate textual description of a graphical object, that may include face markup. In this usage, the <textual-form> element is intended for display in devices that do not possess the full power of a browser or do not have the ability to display graphics. (The element <alt-text> performs a similar function but has an even simpler face-markup-free model for accessibility uses.)
... <fig id="f1"> <caption> <title>Stable and Nondisruptive <italic>In Vitro</italic>/ <italic>In Vivo</italic> Labeling of Mesenchymal Stem Cells</title> <p>by Internalizing Quantum Dots ...</p> </caption> <alternatives> <textual-form> <italic>In Vitro</italic>/<italic>In Vivo</italic> Labeling of Mesenchymal Stem Cells </textual-form> <graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fors2662.f1"> <alt-text>Mesenchymal stem labeling</alt-text> </graphic> </alternatives> </fig> ...