Digital Talking Book Expanded Document Type Definition Documentation for Version V110

3.3. Element Declaration Form

For each of the element declarations the following information is supplied:

1. <!ELEMENT elementname>
2. Description. Repeats the description shown in Section 3.2. If the element is from HTML 4.0 strict, the suffix appears: [XHTML 4.0]
3. Contains: original element content model.
4. Expanded: only if the original has any parameter entity references in its content model, they are fully-expanded.
5. Occurs within: list of element names in which this element may (or must) occur directly, in their content models.
6. Attributes: Original: attribute list
   
7. Expanded: only if the original has any parameter entities.
8. Explanation of any unique attributes.

Element Declarations are shown as:

<!ELEMENT elementname

Contains:
	EMPTY or original content model:
Expanded:
	content model with parameter entities expanded

>

EMPTY declared content denotes that the element has no explicit content. Instead, its purpose is to mark a position, and to associate attribute values to that position. The XML-approved way to indicate the end-tag of such an element is by the special tag close ' />'. Some browsers presume that leading space (after the end of the final quoted value for an attribute).

For example, the XML-preferred way using the EMPTY horizontal rule tag:

<hr title="horizontal rule purpose" />

or for backward compatibility the explicit end tag form may be used:

<hr title="horizontal rule purpose"></hr>

Element content models are formed from a parenthesized list of names of other elements or parameter entities of the form %name; or #PCDATA, separated by connectors:

Connector	Use	Example
,	sequence	(x,y) is x followed by y
|	alternative	(x|y) is either x or y
(...)	grouping	(x,(y|z)) is x followed by either y or z

Individual names or groupings of them may have a following replicator. If there is no replicator, that means just one of what precedes it, possibly a parenthesized expression.

Replicator	Use	Example
?	optional	x? means zero or one of x
*	optional and repeatable	x* means zero or more of x
+	Repeatable	x+ means one or more of x
none	One only	x means just one x

#PCDATA stands for parsed character data. The name suggests that the content may include other inline element tags intermixed as allowed in the content model.

#PCDATA can occur as an entire content model. Or, it can occur first among alternatives. For examples:

Content Model	Meaning
(x | y)+	Either x or y, repeatable, in any order
(x,y?)	x, optionally followed by y
(x?,(y|z)*)	Optional x, followed by optional and repeatable choice of x or y
(#PCDATA)	Any text or character entities
(#PCDATA | x | y)+	#PCDATA, intermixed and repeatable, with x or y

The final example above with #PCDATA allows choice among 0 or more of x or y intermixed with text. Note that because the #PCDATA is present, even an empty string matches this model.

#PCDATA may also contain character entities that permit representing non-ASCII characters, intermixed with characters from the document character set. If this set is "ISO-8879-1" or the ASCII characters, a form for referencing such non-ASCII entities is:

&xHHHH;

where the HHHH denotes a Unicode hexadecimal code position.

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